| /* |
| * Read-Copy Update mechanism for mutual exclusion |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| * |
| * Copyright IBM Corporation, 2008 |
| * |
| * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
| * Manfred Spraul <manfred@colorfullife.com> |
| * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version |
| * |
| * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
| * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
| * |
| * For detailed explanation of Read-Copy Update mechanism see - |
| * Documentation/RCU |
| */ |
| #include <linux/types.h> |
| #include <linux/kernel.h> |
| #include <linux/init.h> |
| #include <linux/spinlock.h> |
| #include <linux/smp.h> |
| #include <linux/rcupdate.h> |
| #include <linux/interrupt.h> |
| #include <linux/sched.h> |
| #include <linux/nmi.h> |
| #include <linux/atomic.h> |
| #include <linux/bitops.h> |
| #include <linux/export.h> |
| #include <linux/completion.h> |
| #include <linux/moduleparam.h> |
| #include <linux/percpu.h> |
| #include <linux/notifier.h> |
| #include <linux/cpu.h> |
| #include <linux/mutex.h> |
| #include <linux/time.h> |
| #include <linux/kernel_stat.h> |
| #include <linux/wait.h> |
| #include <linux/kthread.h> |
| #include <linux/prefetch.h> |
| #include <linux/delay.h> |
| #include <linux/stop_machine.h> |
| #include <linux/random.h> |
| |
| #include "rcutree.h" |
| #include <trace/events/rcu.h> |
| |
| #include "rcu.h" |
| |
| /* Data structures. */ |
| |
| static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; |
| static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; |
| |
| #define RCU_STATE_INITIALIZER(sname, sabbr, cr) { \ |
| .level = { &sname##_state.node[0] }, \ |
| .call = cr, \ |
| .fqs_state = RCU_GP_IDLE, \ |
| .gpnum = 0UL - 300UL, \ |
| .completed = 0UL - 300UL, \ |
| .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \ |
| .orphan_nxttail = &sname##_state.orphan_nxtlist, \ |
| .orphan_donetail = &sname##_state.orphan_donelist, \ |
| .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ |
| .onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \ |
| .name = #sname, \ |
| .abbr = sabbr, \ |
| } |
| |
| struct rcu_state rcu_sched_state = |
| RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched); |
| DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); |
| |
| struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); |
| DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
| |
| static struct rcu_state *rcu_state; |
| LIST_HEAD(rcu_struct_flavors); |
| |
| /* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */ |
| static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF; |
| module_param(rcu_fanout_leaf, int, 0444); |
| int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; |
| static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */ |
| NUM_RCU_LVL_0, |
| NUM_RCU_LVL_1, |
| NUM_RCU_LVL_2, |
| NUM_RCU_LVL_3, |
| NUM_RCU_LVL_4, |
| }; |
| int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ |
| |
| /* |
| * The rcu_scheduler_active variable transitions from zero to one just |
| * before the first task is spawned. So when this variable is zero, RCU |
| * can assume that there is but one task, allowing RCU to (for example) |
| * optimize synchronize_sched() to a simple barrier(). When this variable |
| * is one, RCU must actually do all the hard work required to detect real |
| * grace periods. This variable is also used to suppress boot-time false |
| * positives from lockdep-RCU error checking. |
| */ |
| int rcu_scheduler_active __read_mostly; |
| EXPORT_SYMBOL_GPL(rcu_scheduler_active); |
| |
| /* |
| * The rcu_scheduler_fully_active variable transitions from zero to one |
| * during the early_initcall() processing, which is after the scheduler |
| * is capable of creating new tasks. So RCU processing (for example, |
| * creating tasks for RCU priority boosting) must be delayed until after |
| * rcu_scheduler_fully_active transitions from zero to one. We also |
| * currently delay invocation of any RCU callbacks until after this point. |
| * |
| * It might later prove better for people registering RCU callbacks during |
| * early boot to take responsibility for these callbacks, but one step at |
| * a time. |
| */ |
| static int rcu_scheduler_fully_active __read_mostly; |
| |
| #ifdef CONFIG_RCU_BOOST |
| |
| /* |
| * Control variables for per-CPU and per-rcu_node kthreads. These |
| * handle all flavors of RCU. |
| */ |
| static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); |
| DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
| DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); |
| DEFINE_PER_CPU(char, rcu_cpu_has_work); |
| |
| #endif /* #ifdef CONFIG_RCU_BOOST */ |
| |
| static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); |
| static void invoke_rcu_core(void); |
| static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); |
| |
| /* |
| * Track the rcutorture test sequence number and the update version |
| * number within a given test. The rcutorture_testseq is incremented |
| * on every rcutorture module load and unload, so has an odd value |
| * when a test is running. The rcutorture_vernum is set to zero |
| * when rcutorture starts and is incremented on each rcutorture update. |
| * These variables enable correlating rcutorture output with the |
| * RCU tracing information. |
| */ |
| unsigned long rcutorture_testseq; |
| unsigned long rcutorture_vernum; |
| |
| /* |
| * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s |
| * permit this function to be invoked without holding the root rcu_node |
| * structure's ->lock, but of course results can be subject to change. |
| */ |
| static int rcu_gp_in_progress(struct rcu_state *rsp) |
| { |
| return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); |
| } |
| |
| /* |
| * Note a quiescent state. Because we do not need to know |
| * how many quiescent states passed, just if there was at least |
| * one since the start of the grace period, this just sets a flag. |
| * The caller must have disabled preemption. |
| */ |
| void rcu_sched_qs(int cpu) |
| { |
| struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
| |
| if (rdp->passed_quiesce == 0) |
| trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs"); |
| rdp->passed_quiesce = 1; |
| } |
| |
| void rcu_bh_qs(int cpu) |
| { |
| struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
| |
| if (rdp->passed_quiesce == 0) |
| trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs"); |
| rdp->passed_quiesce = 1; |
| } |
| |
| /* |
| * Note a context switch. This is a quiescent state for RCU-sched, |
| * and requires special handling for preemptible RCU. |
| * The caller must have disabled preemption. |
| */ |
| void rcu_note_context_switch(int cpu) |
| { |
| trace_rcu_utilization("Start context switch"); |
| rcu_sched_qs(cpu); |
| rcu_preempt_note_context_switch(cpu); |
| trace_rcu_utilization("End context switch"); |
| } |
| EXPORT_SYMBOL_GPL(rcu_note_context_switch); |
| |
| DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
| .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, |
| .dynticks = ATOMIC_INIT(1), |
| }; |
| |
| static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */ |
| static long qhimark = 10000; /* If this many pending, ignore blimit. */ |
| static long qlowmark = 100; /* Once only this many pending, use blimit. */ |
| |
| module_param(blimit, long, 0444); |
| module_param(qhimark, long, 0444); |
| module_param(qlowmark, long, 0444); |
| |
| static ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS; |
| static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS; |
| |
| module_param(jiffies_till_first_fqs, ulong, 0644); |
| module_param(jiffies_till_next_fqs, ulong, 0644); |
| |
| static void rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, |
| struct rcu_data *rdp); |
| static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)); |
| static void force_quiescent_state(struct rcu_state *rsp); |
| static int rcu_pending(int cpu); |
| |
| /* |
| * Return the number of RCU-sched batches processed thus far for debug & stats. |
| */ |
| long rcu_batches_completed_sched(void) |
| { |
| return rcu_sched_state.completed; |
| } |
| EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
| |
| /* |
| * Return the number of RCU BH batches processed thus far for debug & stats. |
| */ |
| long rcu_batches_completed_bh(void) |
| { |
| return rcu_bh_state.completed; |
| } |
| EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); |
| |
| /* |
| * Force a quiescent state for RCU BH. |
| */ |
| void rcu_bh_force_quiescent_state(void) |
| { |
| force_quiescent_state(&rcu_bh_state); |
| } |
| EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); |
| |
| /* |
| * Record the number of times rcutorture tests have been initiated and |
| * terminated. This information allows the debugfs tracing stats to be |
| * correlated to the rcutorture messages, even when the rcutorture module |
| * is being repeatedly loaded and unloaded. In other words, we cannot |
| * store this state in rcutorture itself. |
| */ |
| void rcutorture_record_test_transition(void) |
| { |
| rcutorture_testseq++; |
| rcutorture_vernum = 0; |
| } |
| EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); |
| |
| /* |
| * Record the number of writer passes through the current rcutorture test. |
| * This is also used to correlate debugfs tracing stats with the rcutorture |
| * messages. |
| */ |
| void rcutorture_record_progress(unsigned long vernum) |
| { |
| rcutorture_vernum++; |
| } |
| EXPORT_SYMBOL_GPL(rcutorture_record_progress); |
| |
| /* |
| * Force a quiescent state for RCU-sched. |
| */ |
| void rcu_sched_force_quiescent_state(void) |
| { |
| force_quiescent_state(&rcu_sched_state); |
| } |
| EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); |
| |
| /* |
| * Does the CPU have callbacks ready to be invoked? |
| */ |
| static int |
| cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) |
| { |
| return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] && |
| rdp->nxttail[RCU_DONE_TAIL] != NULL; |
| } |
| |
| /* |
| * Does the current CPU require a not-yet-started grace period? |
| * The caller must have disabled interrupts to prevent races with |
| * normal callback registry. |
| */ |
| static int |
| cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| int i; |
| |
| if (rcu_gp_in_progress(rsp)) |
| return 0; /* No, a grace period is already in progress. */ |
| if (rcu_nocb_needs_gp(rsp)) |
| return 1; /* Yes, a no-CBs CPU needs one. */ |
| if (!rdp->nxttail[RCU_NEXT_TAIL]) |
| return 0; /* No, this is a no-CBs (or offline) CPU. */ |
| if (*rdp->nxttail[RCU_NEXT_READY_TAIL]) |
| return 1; /* Yes, this CPU has newly registered callbacks. */ |
| for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) |
| if (rdp->nxttail[i - 1] != rdp->nxttail[i] && |
| ULONG_CMP_LT(ACCESS_ONCE(rsp->completed), |
| rdp->nxtcompleted[i])) |
| return 1; /* Yes, CBs for future grace period. */ |
| return 0; /* No grace period needed. */ |
| } |
| |
| /* |
| * Return the root node of the specified rcu_state structure. |
| */ |
| static struct rcu_node *rcu_get_root(struct rcu_state *rsp) |
| { |
| return &rsp->node[0]; |
| } |
| |
| /* |
| * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state |
| * |
| * If the new value of the ->dynticks_nesting counter now is zero, |
| * we really have entered idle, and must do the appropriate accounting. |
| * The caller must have disabled interrupts. |
| */ |
| static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval, |
| bool user) |
| { |
| trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting); |
| if (!user && !is_idle_task(current)) { |
| struct task_struct *idle = idle_task(smp_processor_id()); |
| |
| trace_rcu_dyntick("Error on entry: not idle task", oldval, 0); |
| ftrace_dump(DUMP_ORIG); |
| WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
| current->pid, current->comm, |
| idle->pid, idle->comm); /* must be idle task! */ |
| } |
| rcu_prepare_for_idle(smp_processor_id()); |
| /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
| smp_mb__before_atomic_inc(); /* See above. */ |
| atomic_inc(&rdtp->dynticks); |
| smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */ |
| WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); |
| |
| /* |
| * It is illegal to enter an extended quiescent state while |
| * in an RCU read-side critical section. |
| */ |
| rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), |
| "Illegal idle entry in RCU read-side critical section."); |
| rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), |
| "Illegal idle entry in RCU-bh read-side critical section."); |
| rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), |
| "Illegal idle entry in RCU-sched read-side critical section."); |
| } |
| |
| /* |
| * Enter an RCU extended quiescent state, which can be either the |
| * idle loop or adaptive-tickless usermode execution. |
| */ |
| static void rcu_eqs_enter(bool user) |
| { |
| long long oldval; |
| struct rcu_dynticks *rdtp; |
| |
| rdtp = &__get_cpu_var(rcu_dynticks); |
| oldval = rdtp->dynticks_nesting; |
| WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0); |
| if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) |
| rdtp->dynticks_nesting = 0; |
| else |
| rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; |
| rcu_eqs_enter_common(rdtp, oldval, user); |
| } |
| |
| /** |
| * rcu_idle_enter - inform RCU that current CPU is entering idle |
| * |
| * Enter idle mode, in other words, -leave- the mode in which RCU |
| * read-side critical sections can occur. (Though RCU read-side |
| * critical sections can occur in irq handlers in idle, a possibility |
| * handled by irq_enter() and irq_exit().) |
| * |
| * We crowbar the ->dynticks_nesting field to zero to allow for |
| * the possibility of usermode upcalls having messed up our count |
| * of interrupt nesting level during the prior busy period. |
| */ |
| void rcu_idle_enter(void) |
| { |
| unsigned long flags; |
| |
| local_irq_save(flags); |
| rcu_eqs_enter(false); |
| local_irq_restore(flags); |
| } |
| EXPORT_SYMBOL_GPL(rcu_idle_enter); |
| |
| #ifdef CONFIG_RCU_USER_QS |
| /** |
| * rcu_user_enter - inform RCU that we are resuming userspace. |
| * |
| * Enter RCU idle mode right before resuming userspace. No use of RCU |
| * is permitted between this call and rcu_user_exit(). This way the |
| * CPU doesn't need to maintain the tick for RCU maintenance purposes |
| * when the CPU runs in userspace. |
| */ |
| void rcu_user_enter(void) |
| { |
| rcu_eqs_enter(1); |
| } |
| |
| /** |
| * rcu_user_enter_after_irq - inform RCU that we are going to resume userspace |
| * after the current irq returns. |
| * |
| * This is similar to rcu_user_enter() but in the context of a non-nesting |
| * irq. After this call, RCU enters into idle mode when the interrupt |
| * returns. |
| */ |
| void rcu_user_enter_after_irq(void) |
| { |
| unsigned long flags; |
| struct rcu_dynticks *rdtp; |
| |
| local_irq_save(flags); |
| rdtp = &__get_cpu_var(rcu_dynticks); |
| /* Ensure this irq is interrupting a non-idle RCU state. */ |
| WARN_ON_ONCE(!(rdtp->dynticks_nesting & DYNTICK_TASK_MASK)); |
| rdtp->dynticks_nesting = 1; |
| local_irq_restore(flags); |
| } |
| #endif /* CONFIG_RCU_USER_QS */ |
| |
| /** |
| * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle |
| * |
| * Exit from an interrupt handler, which might possibly result in entering |
| * idle mode, in other words, leaving the mode in which read-side critical |
| * sections can occur. |
| * |
| * This code assumes that the idle loop never does anything that might |
| * result in unbalanced calls to irq_enter() and irq_exit(). If your |
| * architecture violates this assumption, RCU will give you what you |
| * deserve, good and hard. But very infrequently and irreproducibly. |
| * |
| * Use things like work queues to work around this limitation. |
| * |
| * You have been warned. |
| */ |
| void rcu_irq_exit(void) |
| { |
| unsigned long flags; |
| long long oldval; |
| struct rcu_dynticks *rdtp; |
| |
| local_irq_save(flags); |
| rdtp = &__get_cpu_var(rcu_dynticks); |
| oldval = rdtp->dynticks_nesting; |
| rdtp->dynticks_nesting--; |
| WARN_ON_ONCE(rdtp->dynticks_nesting < 0); |
| if (rdtp->dynticks_nesting) |
| trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting); |
| else |
| rcu_eqs_enter_common(rdtp, oldval, true); |
| local_irq_restore(flags); |
| } |
| |
| /* |
| * rcu_eqs_exit_common - current CPU moving away from extended quiescent state |
| * |
| * If the new value of the ->dynticks_nesting counter was previously zero, |
| * we really have exited idle, and must do the appropriate accounting. |
| * The caller must have disabled interrupts. |
| */ |
| static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval, |
| int user) |
| { |
| smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ |
| atomic_inc(&rdtp->dynticks); |
| /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ |
| smp_mb__after_atomic_inc(); /* See above. */ |
| WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); |
| rcu_cleanup_after_idle(smp_processor_id()); |
| trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting); |
| if (!user && !is_idle_task(current)) { |
| struct task_struct *idle = idle_task(smp_processor_id()); |
| |
| trace_rcu_dyntick("Error on exit: not idle task", |
| oldval, rdtp->dynticks_nesting); |
| ftrace_dump(DUMP_ORIG); |
| WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
| current->pid, current->comm, |
| idle->pid, idle->comm); /* must be idle task! */ |
| } |
| } |
| |
| /* |
| * Exit an RCU extended quiescent state, which can be either the |
| * idle loop or adaptive-tickless usermode execution. |
| */ |
| static void rcu_eqs_exit(bool user) |
| { |
| struct rcu_dynticks *rdtp; |
| long long oldval; |
| |
| rdtp = &__get_cpu_var(rcu_dynticks); |
| oldval = rdtp->dynticks_nesting; |
| WARN_ON_ONCE(oldval < 0); |
| if (oldval & DYNTICK_TASK_NEST_MASK) |
| rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; |
| else |
| rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
| rcu_eqs_exit_common(rdtp, oldval, user); |
| } |
| |
| /** |
| * rcu_idle_exit - inform RCU that current CPU is leaving idle |
| * |
| * Exit idle mode, in other words, -enter- the mode in which RCU |
| * read-side critical sections can occur. |
| * |
| * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to |
| * allow for the possibility of usermode upcalls messing up our count |
| * of interrupt nesting level during the busy period that is just |
| * now starting. |
| */ |
| void rcu_idle_exit(void) |
| { |
| unsigned long flags; |
| |
| local_irq_save(flags); |
| rcu_eqs_exit(false); |
| local_irq_restore(flags); |
| } |
| EXPORT_SYMBOL_GPL(rcu_idle_exit); |
| |
| #ifdef CONFIG_RCU_USER_QS |
| /** |
| * rcu_user_exit - inform RCU that we are exiting userspace. |
| * |
| * Exit RCU idle mode while entering the kernel because it can |
| * run a RCU read side critical section anytime. |
| */ |
| void rcu_user_exit(void) |
| { |
| rcu_eqs_exit(1); |
| } |
| |
| /** |
| * rcu_user_exit_after_irq - inform RCU that we won't resume to userspace |
| * idle mode after the current non-nesting irq returns. |
| * |
| * This is similar to rcu_user_exit() but in the context of an irq. |
| * This is called when the irq has interrupted a userspace RCU idle mode |
| * context. When the current non-nesting interrupt returns after this call, |
| * the CPU won't restore the RCU idle mode. |
| */ |
| void rcu_user_exit_after_irq(void) |
| { |
| unsigned long flags; |
| struct rcu_dynticks *rdtp; |
| |
| local_irq_save(flags); |
| rdtp = &__get_cpu_var(rcu_dynticks); |
| /* Ensure we are interrupting an RCU idle mode. */ |
| WARN_ON_ONCE(rdtp->dynticks_nesting & DYNTICK_TASK_NEST_MASK); |
| rdtp->dynticks_nesting += DYNTICK_TASK_EXIT_IDLE; |
| local_irq_restore(flags); |
| } |
| #endif /* CONFIG_RCU_USER_QS */ |
| |
| /** |
| * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle |
| * |
| * Enter an interrupt handler, which might possibly result in exiting |
| * idle mode, in other words, entering the mode in which read-side critical |
| * sections can occur. |
| * |
| * Note that the Linux kernel is fully capable of entering an interrupt |
| * handler that it never exits, for example when doing upcalls to |
| * user mode! This code assumes that the idle loop never does upcalls to |
| * user mode. If your architecture does do upcalls from the idle loop (or |
| * does anything else that results in unbalanced calls to the irq_enter() |
| * and irq_exit() functions), RCU will give you what you deserve, good |
| * and hard. But very infrequently and irreproducibly. |
| * |
| * Use things like work queues to work around this limitation. |
| * |
| * You have been warned. |
| */ |
| void rcu_irq_enter(void) |
| { |
| unsigned long flags; |
| struct rcu_dynticks *rdtp; |
| long long oldval; |
| |
| local_irq_save(flags); |
| rdtp = &__get_cpu_var(rcu_dynticks); |
| oldval = rdtp->dynticks_nesting; |
| rdtp->dynticks_nesting++; |
| WARN_ON_ONCE(rdtp->dynticks_nesting == 0); |
| if (oldval) |
| trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting); |
| else |
| rcu_eqs_exit_common(rdtp, oldval, true); |
| local_irq_restore(flags); |
| } |
| |
| /** |
| * rcu_nmi_enter - inform RCU of entry to NMI context |
| * |
| * If the CPU was idle with dynamic ticks active, and there is no |
| * irq handler running, this updates rdtp->dynticks_nmi to let the |
| * RCU grace-period handling know that the CPU is active. |
| */ |
| void rcu_nmi_enter(void) |
| { |
| struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| |
| if (rdtp->dynticks_nmi_nesting == 0 && |
| (atomic_read(&rdtp->dynticks) & 0x1)) |
| return; |
| rdtp->dynticks_nmi_nesting++; |
| smp_mb__before_atomic_inc(); /* Force delay from prior write. */ |
| atomic_inc(&rdtp->dynticks); |
| /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ |
| smp_mb__after_atomic_inc(); /* See above. */ |
| WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); |
| } |
| |
| /** |
| * rcu_nmi_exit - inform RCU of exit from NMI context |
| * |
| * If the CPU was idle with dynamic ticks active, and there is no |
| * irq handler running, this updates rdtp->dynticks_nmi to let the |
| * RCU grace-period handling know that the CPU is no longer active. |
| */ |
| void rcu_nmi_exit(void) |
| { |
| struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| |
| if (rdtp->dynticks_nmi_nesting == 0 || |
| --rdtp->dynticks_nmi_nesting != 0) |
| return; |
| /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ |
| smp_mb__before_atomic_inc(); /* See above. */ |
| atomic_inc(&rdtp->dynticks); |
| smp_mb__after_atomic_inc(); /* Force delay to next write. */ |
| WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); |
| } |
| |
| /** |
| * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle |
| * |
| * If the current CPU is in its idle loop and is neither in an interrupt |
| * or NMI handler, return true. |
| */ |
| int rcu_is_cpu_idle(void) |
| { |
| int ret; |
| |
| preempt_disable(); |
| ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0; |
| preempt_enable(); |
| return ret; |
| } |
| EXPORT_SYMBOL(rcu_is_cpu_idle); |
| |
| #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) |
| |
| /* |
| * Is the current CPU online? Disable preemption to avoid false positives |
| * that could otherwise happen due to the current CPU number being sampled, |
| * this task being preempted, its old CPU being taken offline, resuming |
| * on some other CPU, then determining that its old CPU is now offline. |
| * It is OK to use RCU on an offline processor during initial boot, hence |
| * the check for rcu_scheduler_fully_active. Note also that it is OK |
| * for a CPU coming online to use RCU for one jiffy prior to marking itself |
| * online in the cpu_online_mask. Similarly, it is OK for a CPU going |
| * offline to continue to use RCU for one jiffy after marking itself |
| * offline in the cpu_online_mask. This leniency is necessary given the |
| * non-atomic nature of the online and offline processing, for example, |
| * the fact that a CPU enters the scheduler after completing the CPU_DYING |
| * notifiers. |
| * |
| * This is also why RCU internally marks CPUs online during the |
| * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. |
| * |
| * Disable checking if in an NMI handler because we cannot safely report |
| * errors from NMI handlers anyway. |
| */ |
| bool rcu_lockdep_current_cpu_online(void) |
| { |
| struct rcu_data *rdp; |
| struct rcu_node *rnp; |
| bool ret; |
| |
| if (in_nmi()) |
| return 1; |
| preempt_disable(); |
| rdp = &__get_cpu_var(rcu_sched_data); |
| rnp = rdp->mynode; |
| ret = (rdp->grpmask & rnp->qsmaskinit) || |
| !rcu_scheduler_fully_active; |
| preempt_enable(); |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); |
| |
| #endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ |
| |
| /** |
| * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle |
| * |
| * If the current CPU is idle or running at a first-level (not nested) |
| * interrupt from idle, return true. The caller must have at least |
| * disabled preemption. |
| */ |
| static int rcu_is_cpu_rrupt_from_idle(void) |
| { |
| return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1; |
| } |
| |
| /* |
| * Snapshot the specified CPU's dynticks counter so that we can later |
| * credit them with an implicit quiescent state. Return 1 if this CPU |
| * is in dynticks idle mode, which is an extended quiescent state. |
| */ |
| static int dyntick_save_progress_counter(struct rcu_data *rdp) |
| { |
| rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); |
| return (rdp->dynticks_snap & 0x1) == 0; |
| } |
| |
| /* |
| * Return true if the specified CPU has passed through a quiescent |
| * state by virtue of being in or having passed through an dynticks |
| * idle state since the last call to dyntick_save_progress_counter() |
| * for this same CPU, or by virtue of having been offline. |
| */ |
| static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
| { |
| unsigned int curr; |
| unsigned int snap; |
| |
| curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); |
| snap = (unsigned int)rdp->dynticks_snap; |
| |
| /* |
| * If the CPU passed through or entered a dynticks idle phase with |
| * no active irq/NMI handlers, then we can safely pretend that the CPU |
| * already acknowledged the request to pass through a quiescent |
| * state. Either way, that CPU cannot possibly be in an RCU |
| * read-side critical section that started before the beginning |
| * of the current RCU grace period. |
| */ |
| if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) { |
| trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti"); |
| rdp->dynticks_fqs++; |
| return 1; |
| } |
| |
| /* |
| * Check for the CPU being offline, but only if the grace period |
| * is old enough. We don't need to worry about the CPU changing |
| * state: If we see it offline even once, it has been through a |
| * quiescent state. |
| * |
| * The reason for insisting that the grace period be at least |
| * one jiffy old is that CPUs that are not quite online and that |
| * have just gone offline can still execute RCU read-side critical |
| * sections. |
| */ |
| if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies)) |
| return 0; /* Grace period is not old enough. */ |
| barrier(); |
| if (cpu_is_offline(rdp->cpu)) { |
| trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl"); |
| rdp->offline_fqs++; |
| return 1; |
| } |
| |
| /* |
| * There is a possibility that a CPU in adaptive-ticks state |
| * might run in the kernel with the scheduling-clock tick disabled |
| * for an extended time period. Invoke rcu_kick_nohz_cpu() to |
| * force the CPU to restart the scheduling-clock tick in this |
| * CPU is in this state. |
| */ |
| rcu_kick_nohz_cpu(rdp->cpu); |
| |
| return 0; |
| } |
| |
| static void record_gp_stall_check_time(struct rcu_state *rsp) |
| { |
| rsp->gp_start = jiffies; |
| rsp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check(); |
| } |
| |
| /* |
| * Dump stacks of all tasks running on stalled CPUs. This is a fallback |
| * for architectures that do not implement trigger_all_cpu_backtrace(). |
| * The NMI-triggered stack traces are more accurate because they are |
| * printed by the target CPU. |
| */ |
| static void rcu_dump_cpu_stacks(struct rcu_state *rsp) |
| { |
| int cpu; |
| unsigned long flags; |
| struct rcu_node *rnp; |
| |
| rcu_for_each_leaf_node(rsp, rnp) { |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| if (rnp->qsmask != 0) { |
| for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
| if (rnp->qsmask & (1UL << cpu)) |
| dump_cpu_task(rnp->grplo + cpu); |
| } |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| } |
| |
| static void print_other_cpu_stall(struct rcu_state *rsp) |
| { |
| int cpu; |
| long delta; |
| unsigned long flags; |
| int ndetected = 0; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| long totqlen = 0; |
| |
| /* Only let one CPU complain about others per time interval. */ |
| |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| delta = jiffies - rsp->jiffies_stall; |
| if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| |
| /* |
| * OK, time to rat on our buddy... |
| * See Documentation/RCU/stallwarn.txt for info on how to debug |
| * RCU CPU stall warnings. |
| */ |
| printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks:", |
| rsp->name); |
| print_cpu_stall_info_begin(); |
| rcu_for_each_leaf_node(rsp, rnp) { |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| ndetected += rcu_print_task_stall(rnp); |
| if (rnp->qsmask != 0) { |
| for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
| if (rnp->qsmask & (1UL << cpu)) { |
| print_cpu_stall_info(rsp, |
| rnp->grplo + cpu); |
| ndetected++; |
| } |
| } |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| |
| /* |
| * Now rat on any tasks that got kicked up to the root rcu_node |
| * due to CPU offlining. |
| */ |
| rnp = rcu_get_root(rsp); |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| ndetected += rcu_print_task_stall(rnp); |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| |
| print_cpu_stall_info_end(); |
| for_each_possible_cpu(cpu) |
| totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; |
| pr_cont("(detected by %d, t=%ld jiffies, g=%lu, c=%lu, q=%lu)\n", |
| smp_processor_id(), (long)(jiffies - rsp->gp_start), |
| rsp->gpnum, rsp->completed, totqlen); |
| if (ndetected == 0) |
| printk(KERN_ERR "INFO: Stall ended before state dump start\n"); |
| else if (!trigger_all_cpu_backtrace()) |
| rcu_dump_cpu_stacks(rsp); |
| |
| /* Complain about tasks blocking the grace period. */ |
| |
| rcu_print_detail_task_stall(rsp); |
| |
| force_quiescent_state(rsp); /* Kick them all. */ |
| } |
| |
| static void print_cpu_stall(struct rcu_state *rsp) |
| { |
| int cpu; |
| unsigned long flags; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| long totqlen = 0; |
| |
| /* |
| * OK, time to rat on ourselves... |
| * See Documentation/RCU/stallwarn.txt for info on how to debug |
| * RCU CPU stall warnings. |
| */ |
| printk(KERN_ERR "INFO: %s self-detected stall on CPU", rsp->name); |
| print_cpu_stall_info_begin(); |
| print_cpu_stall_info(rsp, smp_processor_id()); |
| print_cpu_stall_info_end(); |
| for_each_possible_cpu(cpu) |
| totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; |
| pr_cont(" (t=%lu jiffies g=%lu c=%lu q=%lu)\n", |
| jiffies - rsp->gp_start, rsp->gpnum, rsp->completed, totqlen); |
| if (!trigger_all_cpu_backtrace()) |
| dump_stack(); |
| |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
| rsp->jiffies_stall = jiffies + |
| 3 * rcu_jiffies_till_stall_check() + 3; |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| |
| set_need_resched(); /* kick ourselves to get things going. */ |
| } |
| |
| static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long j; |
| unsigned long js; |
| struct rcu_node *rnp; |
| |
| if (rcu_cpu_stall_suppress) |
| return; |
| j = ACCESS_ONCE(jiffies); |
| js = ACCESS_ONCE(rsp->jiffies_stall); |
| rnp = rdp->mynode; |
| if (rcu_gp_in_progress(rsp) && |
| (ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { |
| |
| /* We haven't checked in, so go dump stack. */ |
| print_cpu_stall(rsp); |
| |
| } else if (rcu_gp_in_progress(rsp) && |
| ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { |
| |
| /* They had a few time units to dump stack, so complain. */ |
| print_other_cpu_stall(rsp); |
| } |
| } |
| |
| /** |
| * rcu_cpu_stall_reset - prevent further stall warnings in current grace period |
| * |
| * Set the stall-warning timeout way off into the future, thus preventing |
| * any RCU CPU stall-warning messages from appearing in the current set of |
| * RCU grace periods. |
| * |
| * The caller must disable hard irqs. |
| */ |
| void rcu_cpu_stall_reset(void) |
| { |
| struct rcu_state *rsp; |
| |
| for_each_rcu_flavor(rsp) |
| rsp->jiffies_stall = jiffies + ULONG_MAX / 2; |
| } |
| |
| /* |
| * Update CPU-local rcu_data state to record the newly noticed grace period. |
| * This is used both when we started the grace period and when we notice |
| * that someone else started the grace period. The caller must hold the |
| * ->lock of the leaf rcu_node structure corresponding to the current CPU, |
| * and must have irqs disabled. |
| */ |
| static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| if (rdp->gpnum != rnp->gpnum) { |
| /* |
| * If the current grace period is waiting for this CPU, |
| * set up to detect a quiescent state, otherwise don't |
| * go looking for one. |
| */ |
| rdp->gpnum = rnp->gpnum; |
| trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart"); |
| rdp->passed_quiesce = 0; |
| rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask); |
| zero_cpu_stall_ticks(rdp); |
| } |
| } |
| |
| static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| struct rcu_node *rnp; |
| |
| local_irq_save(flags); |
| rnp = rdp->mynode; |
| if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ |
| !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
| local_irq_restore(flags); |
| return; |
| } |
| __note_new_gpnum(rsp, rnp, rdp); |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| |
| /* |
| * Did someone else start a new RCU grace period start since we last |
| * checked? Update local state appropriately if so. Must be called |
| * on the CPU corresponding to rdp. |
| */ |
| static int |
| check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| int ret = 0; |
| |
| local_irq_save(flags); |
| if (rdp->gpnum != rsp->gpnum) { |
| note_new_gpnum(rsp, rdp); |
| ret = 1; |
| } |
| local_irq_restore(flags); |
| return ret; |
| } |
| |
| /* |
| * Initialize the specified rcu_data structure's callback list to empty. |
| */ |
| static void init_callback_list(struct rcu_data *rdp) |
| { |
| int i; |
| |
| if (init_nocb_callback_list(rdp)) |
| return; |
| rdp->nxtlist = NULL; |
| for (i = 0; i < RCU_NEXT_SIZE; i++) |
| rdp->nxttail[i] = &rdp->nxtlist; |
| } |
| |
| /* |
| * Determine the value that ->completed will have at the end of the |
| * next subsequent grace period. This is used to tag callbacks so that |
| * a CPU can invoke callbacks in a timely fashion even if that CPU has |
| * been dyntick-idle for an extended period with callbacks under the |
| * influence of RCU_FAST_NO_HZ. |
| * |
| * The caller must hold rnp->lock with interrupts disabled. |
| */ |
| static unsigned long rcu_cbs_completed(struct rcu_state *rsp, |
| struct rcu_node *rnp) |
| { |
| /* |
| * If RCU is idle, we just wait for the next grace period. |
| * But we can only be sure that RCU is idle if we are looking |
| * at the root rcu_node structure -- otherwise, a new grace |
| * period might have started, but just not yet gotten around |
| * to initializing the current non-root rcu_node structure. |
| */ |
| if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed) |
| return rnp->completed + 1; |
| |
| /* |
| * Otherwise, wait for a possible partial grace period and |
| * then the subsequent full grace period. |
| */ |
| return rnp->completed + 2; |
| } |
| |
| /* |
| * Trace-event helper function for rcu_start_future_gp() and |
| * rcu_nocb_wait_gp(). |
| */ |
| static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, |
| unsigned long c, char *s) |
| { |
| trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum, |
| rnp->completed, c, rnp->level, |
| rnp->grplo, rnp->grphi, s); |
| } |
| |
| /* |
| * Start some future grace period, as needed to handle newly arrived |
| * callbacks. The required future grace periods are recorded in each |
| * rcu_node structure's ->need_future_gp field. |
| * |
| * The caller must hold the specified rcu_node structure's ->lock. |
| */ |
| static unsigned long __maybe_unused |
| rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| unsigned long c; |
| int i; |
| struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); |
| |
| /* |
| * Pick up grace-period number for new callbacks. If this |
| * grace period is already marked as needed, return to the caller. |
| */ |
| c = rcu_cbs_completed(rdp->rsp, rnp); |
| trace_rcu_future_gp(rnp, rdp, c, "Startleaf"); |
| if (rnp->need_future_gp[c & 0x1]) { |
| trace_rcu_future_gp(rnp, rdp, c, "Prestartleaf"); |
| return c; |
| } |
| |
| /* |
| * If either this rcu_node structure or the root rcu_node structure |
| * believe that a grace period is in progress, then we must wait |
| * for the one following, which is in "c". Because our request |
| * will be noticed at the end of the current grace period, we don't |
| * need to explicitly start one. |
| */ |
| if (rnp->gpnum != rnp->completed || |
| ACCESS_ONCE(rnp->gpnum) != ACCESS_ONCE(rnp->completed)) { |
| rnp->need_future_gp[c & 0x1]++; |
| trace_rcu_future_gp(rnp, rdp, c, "Startedleaf"); |
| return c; |
| } |
| |
| /* |
| * There might be no grace period in progress. If we don't already |
| * hold it, acquire the root rcu_node structure's lock in order to |
| * start one (if needed). |
| */ |
| if (rnp != rnp_root) |
| raw_spin_lock(&rnp_root->lock); |
| |
| /* |
| * Get a new grace-period number. If there really is no grace |
| * period in progress, it will be smaller than the one we obtained |
| * earlier. Adjust callbacks as needed. Note that even no-CBs |
| * CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed. |
| */ |
| c = rcu_cbs_completed(rdp->rsp, rnp_root); |
| for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++) |
| if (ULONG_CMP_LT(c, rdp->nxtcompleted[i])) |
| rdp->nxtcompleted[i] = c; |
| |
| /* |
| * If the needed for the required grace period is already |
| * recorded, trace and leave. |
| */ |
| if (rnp_root->need_future_gp[c & 0x1]) { |
| trace_rcu_future_gp(rnp, rdp, c, "Prestartedroot"); |
| goto unlock_out; |
| } |
| |
| /* Record the need for the future grace period. */ |
| rnp_root->need_future_gp[c & 0x1]++; |
| |
| /* If a grace period is not already in progress, start one. */ |
| if (rnp_root->gpnum != rnp_root->completed) { |
| trace_rcu_future_gp(rnp, rdp, c, "Startedleafroot"); |
| } else { |
| trace_rcu_future_gp(rnp, rdp, c, "Startedroot"); |
| rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp); |
| } |
| unlock_out: |
| if (rnp != rnp_root) |
| raw_spin_unlock(&rnp_root->lock); |
| return c; |
| } |
| |
| /* |
| * Clean up any old requests for the just-ended grace period. Also return |
| * whether any additional grace periods have been requested. Also invoke |
| * rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads |
| * waiting for this grace period to complete. |
| */ |
| static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
| { |
| int c = rnp->completed; |
| int needmore; |
| struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
| |
| rcu_nocb_gp_cleanup(rsp, rnp); |
| rnp->need_future_gp[c & 0x1] = 0; |
| needmore = rnp->need_future_gp[(c + 1) & 0x1]; |
| trace_rcu_future_gp(rnp, rdp, c, needmore ? "CleanupMore" : "Cleanup"); |
| return needmore; |
| } |
| |
| /* |
| * If there is room, assign a ->completed number to any callbacks on |
| * this CPU that have not already been assigned. Also accelerate any |
| * callbacks that were previously assigned a ->completed number that has |
| * since proven to be too conservative, which can happen if callbacks get |
| * assigned a ->completed number while RCU is idle, but with reference to |
| * a non-root rcu_node structure. This function is idempotent, so it does |
| * not hurt to call it repeatedly. |
| * |
| * The caller must hold rnp->lock with interrupts disabled. |
| */ |
| static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, |
| struct rcu_data *rdp) |
| { |
| unsigned long c; |
| int i; |
| |
| /* If the CPU has no callbacks, nothing to do. */ |
| if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) |
| return; |
| |
| /* |
| * Starting from the sublist containing the callbacks most |
| * recently assigned a ->completed number and working down, find the |
| * first sublist that is not assignable to an upcoming grace period. |
| * Such a sublist has something in it (first two tests) and has |
| * a ->completed number assigned that will complete sooner than |
| * the ->completed number for newly arrived callbacks (last test). |
| * |
| * The key point is that any later sublist can be assigned the |
| * same ->completed number as the newly arrived callbacks, which |
| * means that the callbacks in any of these later sublist can be |
| * grouped into a single sublist, whether or not they have already |
| * been assigned a ->completed number. |
| */ |
| c = rcu_cbs_completed(rsp, rnp); |
| for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--) |
| if (rdp->nxttail[i] != rdp->nxttail[i - 1] && |
| !ULONG_CMP_GE(rdp->nxtcompleted[i], c)) |
| break; |
| |
| /* |
| * If there are no sublist for unassigned callbacks, leave. |
| * At the same time, advance "i" one sublist, so that "i" will |
| * index into the sublist where all the remaining callbacks should |
| * be grouped into. |
| */ |
| if (++i >= RCU_NEXT_TAIL) |
| return; |
| |
| /* |
| * Assign all subsequent callbacks' ->completed number to the next |
| * full grace period and group them all in the sublist initially |
| * indexed by "i". |
| */ |
| for (; i <= RCU_NEXT_TAIL; i++) { |
| rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL]; |
| rdp->nxtcompleted[i] = c; |
| } |
| /* Record any needed additional grace periods. */ |
| rcu_start_future_gp(rnp, rdp); |
| |
| /* Trace depending on how much we were able to accelerate. */ |
| if (!*rdp->nxttail[RCU_WAIT_TAIL]) |
| trace_rcu_grace_period(rsp->name, rdp->gpnum, "AccWaitCB"); |
| else |
| trace_rcu_grace_period(rsp->name, rdp->gpnum, "AccReadyCB"); |
| } |
| |
| /* |
| * Move any callbacks whose grace period has completed to the |
| * RCU_DONE_TAIL sublist, then compact the remaining sublists and |
| * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL |
| * sublist. This function is idempotent, so it does not hurt to |
| * invoke it repeatedly. As long as it is not invoked -too- often... |
| * |
| * The caller must hold rnp->lock with interrupts disabled. |
| */ |
| static void rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp, |
| struct rcu_data *rdp) |
| { |
| int i, j; |
| |
| /* If the CPU has no callbacks, nothing to do. */ |
| if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) |
| return; |
| |
| /* |
| * Find all callbacks whose ->completed numbers indicate that they |
| * are ready to invoke, and put them into the RCU_DONE_TAIL sublist. |
| */ |
| for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) { |
| if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i])) |
| break; |
| rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i]; |
| } |
| /* Clean up any sublist tail pointers that were misordered above. */ |
| for (j = RCU_WAIT_TAIL; j < i; j++) |
| rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL]; |
| |
| /* Copy down callbacks to fill in empty sublists. */ |
| for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) { |
| if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL]) |
| break; |
| rdp->nxttail[j] = rdp->nxttail[i]; |
| rdp->nxtcompleted[j] = rdp->nxtcompleted[i]; |
| } |
| |
| /* Classify any remaining callbacks. */ |
| rcu_accelerate_cbs(rsp, rnp, rdp); |
| } |
| |
| /* |
| * Advance this CPU's callbacks, but only if the current grace period |
| * has ended. This may be called only from the CPU to whom the rdp |
| * belongs. In addition, the corresponding leaf rcu_node structure's |
| * ->lock must be held by the caller, with irqs disabled. |
| */ |
| static void |
| __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| /* Did another grace period end? */ |
| if (rdp->completed == rnp->completed) { |
| |
| /* No, so just accelerate recent callbacks. */ |
| rcu_accelerate_cbs(rsp, rnp, rdp); |
| |
| } else { |
| |
| /* Advance callbacks. */ |
| rcu_advance_cbs(rsp, rnp, rdp); |
| |
| /* Remember that we saw this grace-period completion. */ |
| rdp->completed = rnp->completed; |
| trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend"); |
| |
| /* |
| * If we were in an extended quiescent state, we may have |
| * missed some grace periods that others CPUs handled on |
| * our behalf. Catch up with this state to avoid noting |
| * spurious new grace periods. If another grace period |
| * has started, then rnp->gpnum will have advanced, so |
| * we will detect this later on. Of course, any quiescent |
| * states we found for the old GP are now invalid. |
| */ |
| if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) { |
| rdp->gpnum = rdp->completed; |
| rdp->passed_quiesce = 0; |
| } |
| |
| /* |
| * If RCU does not need a quiescent state from this CPU, |
| * then make sure that this CPU doesn't go looking for one. |
| */ |
| if ((rnp->qsmask & rdp->grpmask) == 0) |
| rdp->qs_pending = 0; |
| } |
| } |
| |
| /* |
| * Advance this CPU's callbacks, but only if the current grace period |
| * has ended. This may be called only from the CPU to whom the rdp |
| * belongs. |
| */ |
| static void |
| rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| struct rcu_node *rnp; |
| |
| local_irq_save(flags); |
| rnp = rdp->mynode; |
| if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ |
| !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
| local_irq_restore(flags); |
| return; |
| } |
| __rcu_process_gp_end(rsp, rnp, rdp); |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| |
| /* |
| * Do per-CPU grace-period initialization for running CPU. The caller |
| * must hold the lock of the leaf rcu_node structure corresponding to |
| * this CPU. |
| */ |
| static void |
| rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| /* Prior grace period ended, so advance callbacks for current CPU. */ |
| __rcu_process_gp_end(rsp, rnp, rdp); |
| |
| /* Set state so that this CPU will detect the next quiescent state. */ |
| __note_new_gpnum(rsp, rnp, rdp); |
| } |
| |
| /* |
| * Initialize a new grace period. |
| */ |
| static int rcu_gp_init(struct rcu_state *rsp) |
| { |
| struct rcu_data *rdp; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| raw_spin_lock_irq(&rnp->lock); |
| rsp->gp_flags = 0; /* Clear all flags: New grace period. */ |
| |
| if (rcu_gp_in_progress(rsp)) { |
| /* Grace period already in progress, don't start another. */ |
| raw_spin_unlock_irq(&rnp->lock); |
| return 0; |
| } |
| |
| /* Advance to a new grace period and initialize state. */ |
| rsp->gpnum++; |
| trace_rcu_grace_period(rsp->name, rsp->gpnum, "start"); |
| record_gp_stall_check_time(rsp); |
| raw_spin_unlock_irq(&rnp->lock); |
| |
| /* Exclude any concurrent CPU-hotplug operations. */ |
| mutex_lock(&rsp->onoff_mutex); |
| |
| /* |
| * Set the quiescent-state-needed bits in all the rcu_node |
| * structures for all currently online CPUs in breadth-first order, |
| * starting from the root rcu_node structure, relying on the layout |
| * of the tree within the rsp->node[] array. Note that other CPUs |
| * will access only the leaves of the hierarchy, thus seeing that no |
| * grace period is in progress, at least until the corresponding |
| * leaf node has been initialized. In addition, we have excluded |
| * CPU-hotplug operations. |
| * |
| * The grace period cannot complete until the initialization |
| * process finishes, because this kthread handles both. |
| */ |
| rcu_for_each_node_breadth_first(rsp, rnp) { |
| raw_spin_lock_irq(&rnp->lock); |
| rdp = this_cpu_ptr(rsp->rda); |
| rcu_preempt_check_blocked_tasks(rnp); |
| rnp->qsmask = rnp->qsmaskinit; |
| ACCESS_ONCE(rnp->gpnum) = rsp->gpnum; |
| WARN_ON_ONCE(rnp->completed != rsp->completed); |
| ACCESS_ONCE(rnp->completed) = rsp->completed; |
| if (rnp == rdp->mynode) |
| rcu_start_gp_per_cpu(rsp, rnp, rdp); |
| rcu_preempt_boost_start_gp(rnp); |
| trace_rcu_grace_period_init(rsp->name, rnp->gpnum, |
| rnp->level, rnp->grplo, |
| rnp->grphi, rnp->qsmask); |
| raw_spin_unlock_irq(&rnp->lock); |
| #ifdef CONFIG_PROVE_RCU_DELAY |
| if ((prandom_u32() % (rcu_num_nodes + 1)) == 0 && |
| system_state == SYSTEM_RUNNING) |
| udelay(200); |
| #endif /* #ifdef CONFIG_PROVE_RCU_DELAY */ |
| cond_resched(); |
| } |
| |
| mutex_unlock(&rsp->onoff_mutex); |
| return 1; |
| } |
| |
| /* |
| * Do one round of quiescent-state forcing. |
| */ |
| int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in) |
| { |
| int fqs_state = fqs_state_in; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| rsp->n_force_qs++; |
| if (fqs_state == RCU_SAVE_DYNTICK) { |
| /* Collect dyntick-idle snapshots. */ |
| force_qs_rnp(rsp, dyntick_save_progress_counter); |
| fqs_state = RCU_FORCE_QS; |
| } else { |
| /* Handle dyntick-idle and offline CPUs. */ |
| force_qs_rnp(rsp, rcu_implicit_dynticks_qs); |
| } |
| /* Clear flag to prevent immediate re-entry. */ |
| if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { |
| raw_spin_lock_irq(&rnp->lock); |
| rsp->gp_flags &= ~RCU_GP_FLAG_FQS; |
| raw_spin_unlock_irq(&rnp->lock); |
| } |
| return fqs_state; |
| } |
| |
| /* |
| * Clean up after the old grace period. |
| */ |
| static void rcu_gp_cleanup(struct rcu_state *rsp) |
| { |
| unsigned long gp_duration; |
| int nocb = 0; |
| struct rcu_data *rdp; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| raw_spin_lock_irq(&rnp->lock); |
| gp_duration = jiffies - rsp->gp_start; |
| if (gp_duration > rsp->gp_max) |
| rsp->gp_max = gp_duration; |
| |
| /* |
| * We know the grace period is complete, but to everyone else |
| * it appears to still be ongoing. But it is also the case |
| * that to everyone else it looks like there is nothing that |
| * they can do to advance the grace period. It is therefore |
| * safe for us to drop the lock in order to mark the grace |
| * period as completed in all of the rcu_node structures. |
| */ |
| raw_spin_unlock_irq(&rnp->lock); |
| |
| /* |
| * Propagate new ->completed value to rcu_node structures so |
| * that other CPUs don't have to wait until the start of the next |
| * grace period to process their callbacks. This also avoids |
| * some nasty RCU grace-period initialization races by forcing |
| * the end of the current grace period to be completely recorded in |
| * all of the rcu_node structures before the beginning of the next |
| * grace period is recorded in any of the rcu_node structures. |
| */ |
| rcu_for_each_node_breadth_first(rsp, rnp) { |
| raw_spin_lock_irq(&rnp->lock); |
| ACCESS_ONCE(rnp->completed) = rsp->gpnum; |
| rdp = this_cpu_ptr(rsp->rda); |
| if (rnp == rdp->mynode) |
| __rcu_process_gp_end(rsp, rnp, rdp); |
| nocb += rcu_future_gp_cleanup(rsp, rnp); |
| raw_spin_unlock_irq(&rnp->lock); |
| cond_resched(); |
| } |
| rnp = rcu_get_root(rsp); |
| raw_spin_lock_irq(&rnp->lock); |
| rcu_nocb_gp_set(rnp, nocb); |
| |
| rsp->completed = rsp->gpnum; /* Declare grace period done. */ |
| trace_rcu_grace_period(rsp->name, rsp->completed, "end"); |
| rsp->fqs_state = RCU_GP_IDLE; |
| rdp = this_cpu_ptr(rsp->rda); |
| rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */ |
| if (cpu_needs_another_gp(rsp, rdp)) |
| rsp->gp_flags = 1; |
| raw_spin_unlock_irq(&rnp->lock); |
| } |
| |
| /* |
| * Body of kthread that handles grace periods. |
| */ |
| static int __noreturn rcu_gp_kthread(void *arg) |
| { |
| int fqs_state; |
| unsigned long j; |
| int ret; |
| struct rcu_state *rsp = arg; |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| for (;;) { |
| |
| /* Handle grace-period start. */ |
| for (;;) { |
| wait_event_interruptible(rsp->gp_wq, |
| rsp->gp_flags & |
| RCU_GP_FLAG_INIT); |
| if ((rsp->gp_flags & RCU_GP_FLAG_INIT) && |
| rcu_gp_init(rsp)) |
| break; |
| cond_resched(); |
| flush_signals(current); |
| } |
| |
| /* Handle quiescent-state forcing. */ |
| fqs_state = RCU_SAVE_DYNTICK; |
| j = jiffies_till_first_fqs; |
| if (j > HZ) { |
| j = HZ; |
| jiffies_till_first_fqs = HZ; |
| } |
| for (;;) { |
| rsp->jiffies_force_qs = jiffies + j; |
| ret = wait_event_interruptible_timeout(rsp->gp_wq, |
| (rsp->gp_flags & RCU_GP_FLAG_FQS) || |
| (!ACCESS_ONCE(rnp->qsmask) && |
| !rcu_preempt_blocked_readers_cgp(rnp)), |
| j); |
| /* If grace period done, leave loop. */ |
| if (!ACCESS_ONCE(rnp->qsmask) && |
| !rcu_preempt_blocked_readers_cgp(rnp)) |
| break; |
| /* If time for quiescent-state forcing, do it. */ |
| if (ret == 0 || (rsp->gp_flags & RCU_GP_FLAG_FQS)) { |
| fqs_state = rcu_gp_fqs(rsp, fqs_state); |
| cond_resched(); |
| } else { |
| /* Deal with stray signal. */ |
| cond_resched(); |
| flush_signals(current); |
| } |
| j = jiffies_till_next_fqs; |
| if (j > HZ) { |
| j = HZ; |
| jiffies_till_next_fqs = HZ; |
| } else if (j < 1) { |
| j = 1; |
| jiffies_till_next_fqs = 1; |
| } |
| } |
| |
| /* Handle grace-period end. */ |
| rcu_gp_cleanup(rsp); |
| } |
| } |
| |
| static void rsp_wakeup(struct irq_work *work) |
| { |
| struct rcu_state *rsp = container_of(work, struct rcu_state, wakeup_work); |
| |
| /* Wake up rcu_gp_kthread() to start the grace period. */ |
| wake_up(&rsp->gp_wq); |
| } |
| |
| /* |
| * Start a new RCU grace period if warranted, re-initializing the hierarchy |
| * in preparation for detecting the next grace period. The caller must hold |
| * the root node's ->lock and hard irqs must be disabled. |
| * |
| * Note that it is legal for a dying CPU (which is marked as offline) to |
| * invoke this function. This can happen when the dying CPU reports its |
| * quiescent state. |
| */ |
| static void |
| rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, |
| struct rcu_data *rdp) |
| { |
| if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { |
| /* |
| * Either we have not yet spawned the grace-period |
| * task, this CPU does not need another grace period, |
| * or a grace period is already in progress. |
| * Either way, don't start a new grace period. |
| */ |
| return; |
| } |
| rsp->gp_flags = RCU_GP_FLAG_INIT; |
| |
| /* |
| * We can't do wakeups while holding the rnp->lock, as that |
| * could cause possible deadlocks with the rq->lock. Deter |
| * the wakeup to interrupt context. |
| */ |
| irq_work_queue(&rsp->wakeup_work); |
| } |
| |
| /* |
| * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's |
| * callbacks. Note that rcu_start_gp_advanced() cannot do this because it |
| * is invoked indirectly from rcu_advance_cbs(), which would result in |
| * endless recursion -- or would do so if it wasn't for the self-deadlock |
| * that is encountered beforehand. |
| */ |
| static void |
| rcu_start_gp(struct rcu_state *rsp) |
| { |
| struct rcu_data *rdp = this_cpu_ptr(rsp->rda); |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| /* |
| * If there is no grace period in progress right now, any |
| * callbacks we have up to this point will be satisfied by the |
| * next grace period. Also, advancing the callbacks reduces the |
| * probability of false positives from cpu_needs_another_gp() |
| * resulting in pointless grace periods. So, advance callbacks |
| * then start the grace period! |
| */ |
| rcu_advance_cbs(rsp, rnp, rdp); |
| rcu_start_gp_advanced(rsp, rnp, rdp); |
| } |
| |
| /* |
| * Report a full set of quiescent states to the specified rcu_state |
| * data structure. This involves cleaning up after the prior grace |
| * period and letting rcu_start_gp() start up the next grace period |
| * if one is needed. Note that the caller must hold rnp->lock, which |
| * is released before return. |
| */ |
| static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
| __releases(rcu_get_root(rsp)->lock) |
| { |
| WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
| raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); |
| wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ |
| } |
| |
| /* |
| * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
| * Allows quiescent states for a group of CPUs to be reported at one go |
| * to the specified rcu_node structure, though all the CPUs in the group |
| * must be represented by the same rcu_node structure (which need not be |
| * a leaf rcu_node structure, though it often will be). That structure's |
| * lock must be held upon entry, and it is released before return. |
| */ |
| static void |
| rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
| struct rcu_node *rnp, unsigned long flags) |
| __releases(rnp->lock) |
| { |
| struct rcu_node *rnp_c; |
| |
| /* Walk up the rcu_node hierarchy. */ |
| for (;;) { |
| if (!(rnp->qsmask & mask)) { |
| |
| /* Our bit has already been cleared, so done. */ |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| rnp->qsmask &= ~mask; |
| trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, |
| mask, rnp->qsmask, rnp->level, |
| rnp->grplo, rnp->grphi, |
| !!rnp->gp_tasks); |
| if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
| |
| /* Other bits still set at this level, so done. */ |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| mask = rnp->grpmask; |
| if (rnp->parent == NULL) { |
| |
| /* No more levels. Exit loop holding root lock. */ |
| |
| break; |
| } |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| rnp_c = rnp; |
| rnp = rnp->parent; |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| WARN_ON_ONCE(rnp_c->qsmask); |
| } |
| |
| /* |
| * Get here if we are the last CPU to pass through a quiescent |
| * state for this grace period. Invoke rcu_report_qs_rsp() |
| * to clean up and start the next grace period if one is needed. |
| */ |
| rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
| } |
| |
| /* |
| * Record a quiescent state for the specified CPU to that CPU's rcu_data |
| * structure. This must be either called from the specified CPU, or |
| * called when the specified CPU is known to be offline (and when it is |
| * also known that no other CPU is concurrently trying to help the offline |
| * CPU). The lastcomp argument is used to make sure we are still in the |
| * grace period of interest. We don't want to end the current grace period |
| * based on quiescent states detected in an earlier grace period! |
| */ |
| static void |
| rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| unsigned long mask; |
| struct rcu_node *rnp; |
| |
| rnp = rdp->mynode; |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum || |
| rnp->completed == rnp->gpnum) { |
| |
| /* |
| * The grace period in which this quiescent state was |
| * recorded has ended, so don't report it upwards. |
| * We will instead need a new quiescent state that lies |
| * within the current grace period. |
| */ |
| rdp->passed_quiesce = 0; /* need qs for new gp. */ |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| mask = rdp->grpmask; |
| if ((rnp->qsmask & mask) == 0) { |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } else { |
| rdp->qs_pending = 0; |
| |
| /* |
| * This GP can't end until cpu checks in, so all of our |
| * callbacks can be processed during the next GP. |
| */ |
| rcu_accelerate_cbs(rsp, rnp, rdp); |
| |
| rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
| } |
| } |
| |
| /* |
| * Check to see if there is a new grace period of which this CPU |
| * is not yet aware, and if so, set up local rcu_data state for it. |
| * Otherwise, see if this CPU has just passed through its first |
| * quiescent state for this grace period, and record that fact if so. |
| */ |
| static void |
| rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| /* If there is now a new grace period, record and return. */ |
| if (check_for_new_grace_period(rsp, rdp)) |
| return; |
| |
| /* |
| * Does this CPU still need to do its part for current grace period? |
| * If no, return and let the other CPUs do their part as well. |
| */ |
| if (!rdp->qs_pending) |
| return; |
| |
| /* |
| * Was there a quiescent state since the beginning of the grace |
| * period? If no, then exit and wait for the next call. |
| */ |
| if (!rdp->passed_quiesce) |
| return; |
| |
| /* |
| * Tell RCU we are done (but rcu_report_qs_rdp() will be the |
| * judge of that). |
| */ |
| rcu_report_qs_rdp(rdp->cpu, rsp, rdp); |
| } |
| |
| #ifdef CONFIG_HOTPLUG_CPU |
| |
| /* |
| * Send the specified CPU's RCU callbacks to the orphanage. The |
| * specified CPU must be offline, and the caller must hold the |
| * ->orphan_lock. |
| */ |
| static void |
| rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, |
| struct rcu_node *rnp, struct rcu_data *rdp) |
| { |
| /* No-CBs CPUs do not have orphanable callbacks. */ |
| if (rcu_is_nocb_cpu(rdp->cpu)) |
| return; |
| |
| /* |
| * Orphan the callbacks. First adjust the counts. This is safe |
| * because _rcu_barrier() excludes CPU-hotplug operations, so it |
| * cannot be running now. Thus no memory barrier is required. |
| */ |
| if (rdp->nxtlist != NULL) { |
| rsp->qlen_lazy += rdp->qlen_lazy; |
| rsp->qlen += rdp->qlen; |
| rdp->n_cbs_orphaned += rdp->qlen; |
| rdp->qlen_lazy = 0; |
| ACCESS_ONCE(rdp->qlen) = 0; |
| } |
| |
| /* |
| * Next, move those callbacks still needing a grace period to |
| * the orphanage, where some other CPU will pick them up. |
| * Some of the callbacks might have gone partway through a grace |
| * period, but that is too bad. They get to start over because we |
| * cannot assume that grace periods are synchronized across CPUs. |
| * We don't bother updating the ->nxttail[] array yet, instead |
| * we just reset the whole thing later on. |
| */ |
| if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) { |
| *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL]; |
| rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL]; |
| *rdp->nxttail[RCU_DONE_TAIL] = NULL; |
| } |
| |
| /* |
| * Then move the ready-to-invoke callbacks to the orphanage, |
| * where some other CPU will pick them up. These will not be |
| * required to pass though another grace period: They are done. |
| */ |
| if (rdp->nxtlist != NULL) { |
| *rsp->orphan_donetail = rdp->nxtlist; |
| rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL]; |
| } |
| |
| /* Finally, initialize the rcu_data structure's list to empty. */ |
| init_callback_list(rdp); |
| } |
| |
| /* |
| * Adopt the RCU callbacks from the specified rcu_state structure's |
| * orphanage. The caller must hold the ->orphan_lock. |
| */ |
| static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
| { |
| int i; |
| struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); |
| |
| /* No-CBs CPUs are handled specially. */ |
| if (rcu_nocb_adopt_orphan_cbs(rsp, rdp)) |
| return; |
| |
| /* Do the accounting first. */ |
| rdp->qlen_lazy += rsp->qlen_lazy; |
| rdp->qlen += rsp->qlen; |
| rdp->n_cbs_adopted += rsp->qlen; |
| if (rsp->qlen_lazy != rsp->qlen) |
| rcu_idle_count_callbacks_posted(); |
| rsp->qlen_lazy = 0; |
| rsp->qlen = 0; |
| |
| /* |
| * We do not need a memory barrier here because the only way we |
| * can get here if there is an rcu_barrier() in flight is if |
| * we are the task doing the rcu_barrier(). |
| */ |
| |
| /* First adopt the ready-to-invoke callbacks. */ |
| if (rsp->orphan_donelist != NULL) { |
| *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL]; |
| *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist; |
| for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--) |
| if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) |
| rdp->nxttail[i] = rsp->orphan_donetail; |
| rsp->orphan_donelist = NULL; |
| rsp->orphan_donetail = &rsp->orphan_donelist; |
| } |
| |
| /* And then adopt the callbacks that still need a grace period. */ |
| if (rsp->orphan_nxtlist != NULL) { |
| *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist; |
| rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail; |
| rsp->orphan_nxtlist = NULL; |
| rsp->orphan_nxttail = &rsp->orphan_nxtlist; |
| } |
| } |
| |
| /* |
| * Trace the fact that this CPU is going offline. |
| */ |
| static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) |
| { |
| RCU_TRACE(unsigned long mask); |
| RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda)); |
| RCU_TRACE(struct rcu_node *rnp = rdp->mynode); |
| |
| RCU_TRACE(mask = rdp->grpmask); |
| trace_rcu_grace_period(rsp->name, |
| rnp->gpnum + 1 - !!(rnp->qsmask & mask), |
| "cpuofl"); |
| } |
| |
| /* |
| * The CPU has been completely removed, and some other CPU is reporting |
| * this fact from process context. Do the remainder of the cleanup, |
| * including orphaning the outgoing CPU's RCU callbacks, and also |
| * adopting them. There can only be one CPU hotplug operation at a time, |
| * so no other CPU can be attempting to update rcu_cpu_kthread_task. |
| */ |
| static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| unsigned long mask; |
| int need_report = 0; |
| struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
| struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ |
| |
| /* Adjust any no-longer-needed kthreads. */ |
| rcu_boost_kthread_setaffinity(rnp, -1); |
| |
| /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */ |
| |
| /* Exclude any attempts to start a new grace period. */ |
| mutex_lock(&rsp->onoff_mutex); |
| raw_spin_lock_irqsave(&rsp->orphan_lock, flags); |
| |
| /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */ |
| rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); |
| rcu_adopt_orphan_cbs(rsp); |
| |
| /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
| mask = rdp->grpmask; /* rnp->grplo is constant. */ |
| do { |
| raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| rnp->qsmaskinit &= ~mask; |
| if (rnp->qsmaskinit != 0) { |
| if (rnp != rdp->mynode) |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| break; |
| } |
| if (rnp == rdp->mynode) |
| need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); |
| else |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| mask = rnp->grpmask; |
| rnp = rnp->parent; |
| } while (rnp != NULL); |
| |
| /* |
| * We still hold the leaf rcu_node structure lock here, and |
| * irqs are still disabled. The reason for this subterfuge is |
| * because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock |
| * held leads to deadlock. |
| */ |
| raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */ |
| rnp = rdp->mynode; |
| if (need_report & RCU_OFL_TASKS_NORM_GP) |
| rcu_report_unblock_qs_rnp(rnp, flags); |
| else |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| if (need_report & RCU_OFL_TASKS_EXP_GP) |
| rcu_report_exp_rnp(rsp, rnp, true); |
| WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL, |
| "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n", |
| cpu, rdp->qlen, rdp->nxtlist); |
| init_callback_list(rdp); |
| /* Disallow further callbacks on this CPU. */ |
| rdp->nxttail[RCU_NEXT_TAIL] = NULL; |
| mutex_unlock(&rsp->onoff_mutex); |
| } |
| |
| #else /* #ifdef CONFIG_HOTPLUG_CPU */ |
| |
| static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) |
| { |
| } |
| |
| static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) |
| { |
| } |
| |
| #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ |
| |
| /* |
| * Invoke any RCU callbacks that have made it to the end of their grace |
| * period. Thottle as specified by rdp->blimit. |
| */ |
| static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| unsigned long flags; |
| struct rcu_head *next, *list, **tail; |
| long bl, count, count_lazy; |
| int i; |
| |
| /* If no callbacks are ready, just return. */ |
| if (!cpu_has_callbacks_ready_to_invoke(rdp)) { |
| trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0); |
| trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist), |
| need_resched(), is_idle_task(current), |
| rcu_is_callbacks_kthread()); |
| return; |
| } |
| |
| /* |
| * Extract the list of ready callbacks, disabling to prevent |
| * races with call_rcu() from interrupt handlers. |
| */ |
| local_irq_save(flags); |
| WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); |
| bl = rdp->blimit; |
| trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl); |
| list = rdp->nxtlist; |
| rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; |
| *rdp->nxttail[RCU_DONE_TAIL] = NULL; |
| tail = rdp->nxttail[RCU_DONE_TAIL]; |
| for (i = RCU_NEXT_SIZE - 1; i >= 0; i--) |
| if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) |
| rdp->nxttail[i] = &rdp->nxtlist; |
| local_irq_restore(flags); |
| |
| /* Invoke callbacks. */ |
| count = count_lazy = 0; |
| while (list) { |
| next = list->next; |
| prefetch(next); |
| debug_rcu_head_unqueue(list); |
| if (__rcu_reclaim(rsp->name, list)) |
| count_lazy++; |
| list = next; |
| /* Stop only if limit reached and CPU has something to do. */ |
| if (++count >= bl && |
| (need_resched() || |
| (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) |
| break; |
| } |
| |
| local_irq_save(flags); |
| trace_rcu_batch_end(rsp->name, count, !!list, need_resched(), |
| is_idle_task(current), |
| rcu_is_callbacks_kthread()); |
| |
| /* Update count, and requeue any remaining callbacks. */ |
| if (list != NULL) { |
| *tail = rdp->nxtlist; |
| rdp->nxtlist = list; |
| for (i = 0; i < RCU_NEXT_SIZE; i++) |
| if (&rdp->nxtlist == rdp->nxttail[i]) |
| rdp->nxttail[i] = tail; |
| else |
| break; |
| } |
| smp_mb(); /* List handling before counting for rcu_barrier(). */ |
| rdp->qlen_lazy -= count_lazy; |
| ACCESS_ONCE(rdp->qlen) -= count; |
| rdp->n_cbs_invoked += count; |
| |
| /* Reinstate batch limit if we have worked down the excess. */ |
| if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) |
| rdp->blimit = blimit; |
| |
| /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
| if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { |
| rdp->qlen_last_fqs_check = 0; |
| rdp->n_force_qs_snap = rsp->n_force_qs; |
| } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) |
| rdp->qlen_last_fqs_check = rdp->qlen; |
| WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0)); |
| |
| local_irq_restore(flags); |
| |
| /* Re-invoke RCU core processing if there are callbacks remaining. */ |
| if (cpu_has_callbacks_ready_to_invoke(rdp)) |
| invoke_rcu_core(); |
| } |
| |
| /* |
| * Check to see if this CPU is in a non-context-switch quiescent state |
| * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). |
| * Also schedule RCU core processing. |
| * |
| * This function must be called from hardirq context. It is normally |
| * invoked from the scheduling-clock interrupt. If rcu_pending returns |
| * false, there is no point in invoking rcu_check_callbacks(). |
| */ |
| void rcu_check_callbacks(int cpu, int user) |
| { |
| trace_rcu_utilization("Start scheduler-tick"); |
| increment_cpu_stall_ticks(); |
| if (user || rcu_is_cpu_rrupt_from_idle()) { |
| |
| /* |
| * Get here if this CPU took its interrupt from user |
| * mode or from the idle loop, and if this is not a |
| * nested interrupt. In this case, the CPU is in |
| * a quiescent state, so note it. |
| * |
| * No memory barrier is required here because both |
| * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
| * variables that other CPUs neither access nor modify, |
| * at least not while the corresponding CPU is online. |
| */ |
| |
| rcu_sched_qs(cpu); |
| rcu_bh_qs(cpu); |
| |
| } else if (!in_softirq()) { |
| |
| /* |
| * Get here if this CPU did not take its interrupt from |
| * softirq, in other words, if it is not interrupting |
| * a rcu_bh read-side critical section. This is an _bh |
| * critical section, so note it. |
| */ |
| |
| rcu_bh_qs(cpu); |
| } |
| rcu_preempt_check_callbacks(cpu); |
| if (rcu_pending(cpu)) |
| invoke_rcu_core(); |
| trace_rcu_utilization("End scheduler-tick"); |
| } |
| |
| /* |
| * Scan the leaf rcu_node structures, processing dyntick state for any that |
| * have not yet encountered a quiescent state, using the function specified. |
| * Also initiate boosting for any threads blocked on the root rcu_node. |
| * |
| * The caller must have suppressed start of new grace periods. |
| */ |
| static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
| { |
| unsigned long bit; |
| int cpu; |
| unsigned long flags; |
| unsigned long mask; |
| struct rcu_node *rnp; |
| |
| rcu_for_each_leaf_node(rsp, rnp) { |
| cond_resched(); |
| mask = 0; |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| if (!rcu_gp_in_progress(rsp)) { |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| return; |
| } |
| if (rnp->qsmask == 0) { |
| rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
| continue; |
| } |
| cpu = rnp->grplo; |
| bit = 1; |
| for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
| if ((rnp->qsmask & bit) != 0 && |
| f(per_cpu_ptr(rsp->rda, cpu))) |
| mask |= bit; |
| } |
| if (mask != 0) { |
| |
| /* rcu_report_qs_rnp() releases rnp->lock. */ |
| rcu_report_qs_rnp(mask, rsp, rnp, flags); |
| continue; |
| } |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| rnp = rcu_get_root(rsp); |
| if (rnp->qsmask == 0) { |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ |
| } |
| } |
| |
| /* |
| * Force quiescent states on reluctant CPUs, and also detect which |
| * CPUs are in dyntick-idle mode. |
| */ |
| static void force_quiescent_state(struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| bool ret; |
| struct rcu_node *rnp; |
| struct rcu_node *rnp_old = NULL; |
| |
| /* Funnel through hierarchy to reduce memory contention. */ |
| rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode; |
| for (; rnp != NULL; rnp = rnp->parent) { |
| ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || |
| !raw_spin_trylock(&rnp->fqslock); |
| if (rnp_old != NULL) |
| raw_spin_unlock(&rnp_old->fqslock); |
| if (ret) { |
| rsp->n_force_qs_lh++; |
| return; |
| } |
| rnp_old = rnp; |
| } |
| /* rnp_old == rcu_get_root(rsp), rnp == NULL. */ |
| |
| /* Reached the root of the rcu_node tree, acquire lock. */ |
| raw_spin_lock_irqsave(&rnp_old->lock, flags); |
| raw_spin_unlock(&rnp_old->fqslock); |
| if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { |
| rsp->n_force_qs_lh++; |
| raw_spin_unlock_irqrestore(&rnp_old->lock, flags); |
| return; /* Someone beat us to it. */ |
| } |
| rsp->gp_flags |= RCU_GP_FLAG_FQS; |
| raw_spin_unlock_irqrestore(&rnp_old->lock, flags); |
| wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ |
| } |
| |
| /* |
| * This does the RCU core processing work for the specified rcu_state |
| * and rcu_data structures. This may be called only from the CPU to |
| * whom the rdp belongs. |
| */ |
| static void |
| __rcu_process_callbacks(struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); |
| |
| WARN_ON_ONCE(rdp->beenonline == 0); |
| |
| /* Handle the end of a grace period that some other CPU ended. */ |
| rcu_process_gp_end(rsp, rdp); |
| |
| /* Update RCU state based on any recent quiescent states. */ |
| rcu_check_quiescent_state(rsp, rdp); |
| |
| /* Does this CPU require a not-yet-started grace period? */ |
| local_irq_save(flags); |
| if (cpu_needs_another_gp(rsp, rdp)) { |
| raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */ |
| rcu_start_gp(rsp); |
| raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); |
| } else { |
| local_irq_restore(flags); |
| } |
| |
| /* If there are callbacks ready, invoke them. */ |
| if (cpu_has_callbacks_ready_to_invoke(rdp)) |
| invoke_rcu_callbacks(rsp, rdp); |
| } |
| |
| /* |
| * Do RCU core processing for the current CPU. |
| */ |
| static void rcu_process_callbacks(struct softirq_action *unused) |
| { |
| struct rcu_state *rsp; |
| |
| if (cpu_is_offline(smp_processor_id())) |
| return; |
| trace_rcu_utilization("Start RCU core"); |
| for_each_rcu_flavor(rsp) |
| __rcu_process_callbacks(rsp); |
| trace_rcu_utilization("End RCU core"); |
| } |
| |
| /* |
| * Schedule RCU callback invocation. If the specified type of RCU |
| * does not support RCU priority boosting, just do a direct call, |
| * otherwise wake up the per-CPU kernel kthread. Note that because we |
| * are running on the current CPU with interrupts disabled, the |
| * rcu_cpu_kthread_task cannot disappear out from under us. |
| */ |
| static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active))) |
| return; |
| if (likely(!rsp->boost)) { |
| rcu_do_batch(rsp, rdp); |
| return; |
| } |
| invoke_rcu_callbacks_kthread(); |
| } |
| |
| static void invoke_rcu_core(void) |
| { |
| if (cpu_online(smp_processor_id())) |
| raise_softirq(RCU_SOFTIRQ); |
| } |
| |
| /* |
| * Handle any core-RCU processing required by a call_rcu() invocation. |
| */ |
| static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, |
| struct rcu_head *head, unsigned long flags) |
| { |
| /* |
| * If called from an extended quiescent state, invoke the RCU |
| * core in order to force a re-evaluation of RCU's idleness. |
| */ |
| if (rcu_is_cpu_idle() && cpu_online(smp_processor_id())) |
| invoke_rcu_core(); |
| |
| /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ |
| if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) |
| return; |
| |
| /* |
| * Force the grace period if too many callbacks or too long waiting. |
| * Enforce hysteresis, and don't invoke force_quiescent_state() |
| * if some other CPU has recently done so. Also, don't bother |
| * invoking force_quiescent_state() if the newly enqueued callback |
| * is the only one waiting for a grace period to complete. |
| */ |
| if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
| |
| /* Are we ignoring a completed grace period? */ |
| rcu_process_gp_end(rsp, rdp); |
| check_for_new_grace_period(rsp, rdp); |
| |
| /* Start a new grace period if one not already started. */ |
| if (!rcu_gp_in_progress(rsp)) { |
| struct rcu_node *rnp_root = rcu_get_root(rsp); |
| |
| raw_spin_lock(&rnp_root->lock); |
| rcu_start_gp(rsp); |
| raw_spin_unlock(&rnp_root->lock); |
| } else { |
| /* Give the grace period a kick. */ |
| rdp->blimit = LONG_MAX; |
| if (rsp->n_force_qs == rdp->n_force_qs_snap && |
| *rdp->nxttail[RCU_DONE_TAIL] != head) |
| force_quiescent_state(rsp); |
| rdp->n_force_qs_snap = rsp->n_force_qs; |
| rdp->qlen_last_fqs_check = rdp->qlen; |
| } |
| } |
| } |
| |
| /* |
| * Helper function for call_rcu() and friends. The cpu argument will |
| * normally be -1, indicating "currently running CPU". It may specify |
| * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier() |
| * is expected to specify a CPU. |
| */ |
| static void |
| __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), |
| struct rcu_state *rsp, int cpu, bool lazy) |
| { |
| unsigned long flags; |
| struct rcu_data *rdp; |
| |
| WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ |
| debug_rcu_head_queue(head); |
| head->func = func; |
| head->next = NULL; |
| |
| /* |
| * Opportunistically note grace-period endings and beginnings. |
| * Note that we might see a beginning right after we see an |
| * end, but never vice versa, since this CPU has to pass through |
| * a quiescent state betweentimes. |
| */ |
| local_irq_save(flags); |
| rdp = this_cpu_ptr(rsp->rda); |
| |
| /* Add the callback to our list. */ |
| if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL) || cpu != -1) { |
| int offline; |
| |
| if (cpu != -1) |
| rdp = per_cpu_ptr(rsp->rda, cpu); |
| offline = !__call_rcu_nocb(rdp, head, lazy); |
| WARN_ON_ONCE(offline); |
| /* _call_rcu() is illegal on offline CPU; leak the callback. */ |
| local_irq_restore(flags); |
| return; |
| } |
| ACCESS_ONCE(rdp->qlen)++; |
| if (lazy) |
| rdp->qlen_lazy++; |
| else |
| rcu_idle_count_callbacks_posted(); |
| smp_mb(); /* Count before adding callback for rcu_barrier(). */ |
| *rdp->nxttail[RCU_NEXT_TAIL] = head; |
| rdp->nxttail[RCU_NEXT_TAIL] = &head->next; |
| |
| if (__is_kfree_rcu_offset((unsigned long)func)) |
| trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, |
| rdp->qlen_lazy, rdp->qlen); |
| else |
| trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen); |
| |
| /* Go handle any RCU core processing required. */ |
| __call_rcu_core(rsp, rdp, head, flags); |
| local_irq_restore(flags); |
| } |
| |
| /* |
| * Queue an RCU-sched callback for invocation after a grace period. |
| */ |
| void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| { |
| __call_rcu(head, func, &rcu_sched_state, -1, 0); |
| } |
| EXPORT_SYMBOL_GPL(call_rcu_sched); |
| |
| /* |
| * Queue an RCU callback for invocation after a quicker grace period. |
| */ |
| void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| { |
| __call_rcu(head, func, &rcu_bh_state, -1, 0); |
| } |
| EXPORT_SYMBOL_GPL(call_rcu_bh); |
| |
| /* |
| * Because a context switch is a grace period for RCU-sched and RCU-bh, |
| * any blocking grace-period wait automatically implies a grace period |
| * if there is only one CPU online at any point time during execution |
| * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to |
| * occasionally incorrectly indicate that there are multiple CPUs online |
| * when there was in fact only one the whole time, as this just adds |
| * some overhead: RCU still operates correctly. |
| */ |
| static inline int rcu_blocking_is_gp(void) |
| { |
| int ret; |
| |
| might_sleep(); /* Check for RCU read-side critical section. */ |
| preempt_disable(); |
| ret = num_online_cpus() <= 1; |
| preempt_enable(); |
| return ret; |
| } |
| |
| /** |
| * synchronize_sched - wait until an rcu-sched grace period has elapsed. |
| * |
| * Control will return to the caller some time after a full rcu-sched |
| * grace period has elapsed, in other words after all currently executing |
| * rcu-sched read-side critical sections have completed. These read-side |
| * critical sections are delimited by rcu_read_lock_sched() and |
| * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), |
| * local_irq_disable(), and so on may be used in place of |
| * rcu_read_lock_sched(). |
| * |
| * This means that all preempt_disable code sequences, including NMI and |
| * non-threaded hardware-interrupt handlers, in progress on entry will |
| * have completed before this primitive returns. However, this does not |
| * guarantee that softirq handlers will have completed, since in some |
| * kernels, these handlers can run in process context, and can block. |
| * |
| * Note that this guarantee implies further memory-ordering guarantees. |
| * On systems with more than one CPU, when synchronize_sched() returns, |
| * each CPU is guaranteed to have executed a full memory barrier since the |
| * end of its last RCU-sched read-side critical section whose beginning |
| * preceded the call to synchronize_sched(). In addition, each CPU having |
| * an RCU read-side critical section that extends beyond the return from |
| * synchronize_sched() is guaranteed to have executed a full memory barrier |
| * after the beginning of synchronize_sched() and before the beginning of |
| * that RCU read-side critical section. Note that these guarantees include |
| * CPUs that are offline, idle, or executing in user mode, as well as CPUs |
| * that are executing in the kernel. |
| * |
| * Furthermore, if CPU A invoked synchronize_sched(), which returned |
| * to its caller on CPU B, then both CPU A and CPU B are guaranteed |
| * to have executed a full memory barrier during the execution of |
| * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but |
| * again only if the system has more than one CPU). |
| * |
| * This primitive provides the guarantees made by the (now removed) |
| * synchronize_kernel() API. In contrast, synchronize_rcu() only |
| * guarantees that rcu_read_lock() sections will have completed. |
| * In "classic RCU", these two guarantees happen to be one and |
| * the same, but can differ in realtime RCU implementations. |
| */ |
| void synchronize_sched(void) |
| { |
| rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
| !lock_is_held(&rcu_lock_map) && |
| !lock_is_held(&rcu_sched_lock_map), |
| "Illegal synchronize_sched() in RCU-sched read-side critical section"); |
| if (rcu_blocking_is_gp()) |
| return; |
| if (rcu_expedited) |
| synchronize_sched_expedited(); |
| else |
| wait_rcu_gp(call_rcu_sched); |
| } |
| EXPORT_SYMBOL_GPL(synchronize_sched); |
| |
| /** |
| * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. |
| * |
| * Control will return to the caller some time after a full rcu_bh grace |
| * period has elapsed, in other words after all currently executing rcu_bh |
| * read-side critical sections have completed. RCU read-side critical |
| * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), |
| * and may be nested. |
| * |
| * See the description of synchronize_sched() for more detailed information |
| * on memory ordering guarantees. |
| */ |
| void synchronize_rcu_bh(void) |
| { |
| rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
| !lock_is_held(&rcu_lock_map) && |
| !lock_is_held(&rcu_sched_lock_map), |
| "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); |
| if (rcu_blocking_is_gp()) |
| return; |
| if (rcu_expedited) |
| synchronize_rcu_bh_expedited(); |
| else |
| wait_rcu_gp(call_rcu_bh); |
| } |
| EXPORT_SYMBOL_GPL(synchronize_rcu_bh); |
| |
| static int synchronize_sched_expedited_cpu_stop(void *data) |
| { |
| /* |
| * There must be a full memory barrier on each affected CPU |
| * between the time that try_stop_cpus() is called and the |
| * time that it returns. |
| * |
| * In the current initial implementation of cpu_stop, the |
| * above condition is already met when the control reaches |
| * this point and the following smp_mb() is not strictly |
| * necessary. Do smp_mb() anyway for documentation and |
| * robustness against future implementation changes. |
| */ |
| smp_mb(); /* See above comment block. */ |
| return 0; |
| } |
| |
| /** |
| * synchronize_sched_expedited - Brute-force RCU-sched grace period |
| * |
| * Wait for an RCU-sched grace period to elapse, but use a "big hammer" |
| * approach to force the grace period to end quickly. This consumes |
| * significant time on all CPUs and is unfriendly to real-time workloads, |
| * so is thus not recommended for any sort of common-case code. In fact, |
| * if you are using synchronize_sched_expedited() in a loop, please |
| * restructure your code to batch your updates, and then use a single |
| * synchronize_sched() instead. |
| * |
| * Note that it is illegal to call this function while holding any lock |
| * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal |
| * to call this function from a CPU-hotplug notifier. Failing to observe |
| * these restriction will result in deadlock. |
| * |
| * This implementation can be thought of as an application of ticket |
| * locking to RCU, with sync_sched_expedited_started and |
| * sync_sched_expedited_done taking on the roles of the halves |
| * of the ticket-lock word. Each task atomically increments |
| * sync_sched_expedited_started upon entry, snapshotting the old value, |
| * then attempts to stop all the CPUs. If this succeeds, then each |
| * CPU will have executed a context switch, resulting in an RCU-sched |
| * grace period. We are then done, so we use atomic_cmpxchg() to |
| * update sync_sched_expedited_done to match our snapshot -- but |
| * only if someone else has not already advanced past our snapshot. |
| * |
| * On the other hand, if try_stop_cpus() fails, we check the value |
| * of sync_sched_expedited_done. If it has advanced past our |
| * initial snapshot, then someone else must have forced a grace period |
| * some time after we took our snapshot. In this case, our work is |
| * done for us, and we can simply return. Otherwise, we try again, |
| * but keep our initial snapshot for purposes of checking for someone |
| * doing our work for us. |
| * |
| * If we fail too many times in a row, we fall back to synchronize_sched(). |
| */ |
| void synchronize_sched_expedited(void) |
| { |
| long firstsnap, s, snap; |
| int trycount = 0; |
| struct rcu_state *rsp = &rcu_sched_state; |
| |
| /* |
| * If we are in danger of counter wrap, just do synchronize_sched(). |
| * By allowing sync_sched_expedited_started to advance no more than |
| * ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring |
| * that more than 3.5 billion CPUs would be required to force a |
| * counter wrap on a 32-bit system. Quite a few more CPUs would of |
| * course be required on a 64-bit system. |
| */ |
| if (ULONG_CMP_GE((ulong)atomic_long_read(&rsp->expedited_start), |
| (ulong)atomic_long_read(&rsp->expedited_done) + |
| ULONG_MAX / 8)) { |
| synchronize_sched(); |
| atomic_long_inc(&rsp->expedited_wrap); |
| return; |
| } |
| |
| /* |
| * Take a ticket. Note that atomic_inc_return() implies a |
| * full memory barrier. |
| */ |
| snap = atomic_long_inc_return(&rsp->expedited_start); |
| firstsnap = snap; |
| get_online_cpus(); |
| WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); |
| |
| /* |
| * Each pass through the following loop attempts to force a |
| * context switch on each CPU. |
| */ |
| while (try_stop_cpus(cpu_online_mask, |
| synchronize_sched_expedited_cpu_stop, |
| NULL) == -EAGAIN) { |
| put_online_cpus(); |
| atomic_long_inc(&rsp->expedited_tryfail); |
| |
| /* Check to see if someone else did our work for us. */ |
| s = atomic_long_read(&rsp->expedited_done); |
| if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) { |
| /* ensure test happens before caller kfree */ |
| smp_mb__before_atomic_inc(); /* ^^^ */ |
| atomic_long_inc(&rsp->expedited_workdone1); |
| return; |
| } |
| |
| /* No joy, try again later. Or just synchronize_sched(). */ |
| if (trycount++ < 10) { |
| udelay(trycount * num_online_cpus()); |
| } else { |
| wait_rcu_gp(call_rcu_sched); |
| atomic_long_inc(&rsp->expedited_normal); |
| return; |
| } |
| |
| /* Recheck to see if someone else did our work for us. */ |
| s = atomic_long_read(&rsp->expedited_done); |
| if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) { |
| /* ensure test happens before caller kfree */ |
| smp_mb__before_atomic_inc(); /* ^^^ */ |
| atomic_long_inc(&rsp->expedited_workdone2); |
| return; |
| } |
| |
| /* |
| * Refetching sync_sched_expedited_started allows later |
| * callers to piggyback on our grace period. We retry |
| * after they started, so our grace period works for them, |
| * and they started after our first try, so their grace |
| * period works for us. |
| */ |
| get_online_cpus(); |
| snap = atomic_long_read(&rsp->expedited_start); |
| smp_mb(); /* ensure read is before try_stop_cpus(). */ |
| } |
| atomic_long_inc(&rsp->expedited_stoppedcpus); |
| |
| /* |
| * Everyone up to our most recent fetch is covered by our grace |
| * period. Update the counter, but only if our work is still |
| * relevant -- which it won't be if someone who started later |
| * than we did already did their update. |
| */ |
| do { |
| atomic_long_inc(&rsp->expedited_done_tries); |
| s = atomic_long_read(&rsp->expedited_done); |
| if (ULONG_CMP_GE((ulong)s, (ulong)snap)) { |
| /* ensure test happens before caller kfree */ |
| smp_mb__before_atomic_inc(); /* ^^^ */ |
| atomic_long_inc(&rsp->expedited_done_lost); |
| break; |
| } |
| } while (atomic_long_cmpxchg(&rsp->expedited_done, s, snap) != s); |
| atomic_long_inc(&rsp->expedited_done_exit); |
| |
| put_online_cpus(); |
| } |
| EXPORT_SYMBOL_GPL(synchronize_sched_expedited); |
| |
| /* |
| * Check to see if there is any immediate RCU-related work to be done |
| * by the current CPU, for the specified type of RCU, returning 1 if so. |
| * The checks are in order of increasing expense: checks that can be |
| * carried out against CPU-local state are performed first. However, |
| * we must check for CPU stalls first, else we might not get a chance. |
| */ |
| static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) |
| { |
| struct rcu_node *rnp = rdp->mynode; |
| |
| rdp->n_rcu_pending++; |
| |
| /* Check for CPU stalls, if enabled. */ |
| check_cpu_stall(rsp, rdp); |
| |
| /* Is the RCU core waiting for a quiescent state from this CPU? */ |
| if (rcu_scheduler_fully_active && |
| rdp->qs_pending && !rdp->passed_quiesce) { |
| rdp->n_rp_qs_pending++; |
| } else if (rdp->qs_pending && rdp->passed_quiesce) { |
| rdp->n_rp_report_qs++; |
| return 1; |
| } |
| |
| /* Does this CPU have callbacks ready to invoke? */ |
| if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
| rdp->n_rp_cb_ready++; |
| return 1; |
| } |
| |
| /* Has RCU gone idle with this CPU needing another grace period? */ |
| if (cpu_needs_another_gp(rsp, rdp)) { |
| rdp->n_rp_cpu_needs_gp++; |
| return 1; |
| } |
| |
| /* Has another RCU grace period completed? */ |
| if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
| rdp->n_rp_gp_completed++; |
| return 1; |
| } |
| |
| /* Has a new RCU grace period started? */ |
| if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
| rdp->n_rp_gp_started++; |
| return 1; |
| } |
| |
| /* nothing to do */ |
| rdp->n_rp_need_nothing++; |
| return 0; |
| } |
| |
| /* |
| * Check to see if there is any immediate RCU-related work to be done |
| * by the current CPU, returning 1 if so. This function is part of the |
| * RCU implementation; it is -not- an exported member of the RCU API. |
| */ |
| static int rcu_pending(int cpu) |
| { |
| struct rcu_state *rsp; |
| |
| for_each_rcu_flavor(rsp) |
| if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu))) |
| return 1; |
| return 0; |
| } |
| |
| /* |
| * Return true if the specified CPU has any callback. If all_lazy is |
| * non-NULL, store an indication of whether all callbacks are lazy. |
| * (If there are no callbacks, all of them are deemed to be lazy.) |
| */ |
| static int rcu_cpu_has_callbacks(int cpu, bool *all_lazy) |
| { |
| bool al = true; |
| bool hc = false; |
| struct rcu_data *rdp; |
| struct rcu_state *rsp; |
| |
| for_each_rcu_flavor(rsp) { |
| rdp = per_cpu_ptr(rsp->rda, cpu); |
| if (rdp->qlen != rdp->qlen_lazy) |
| al = false; |
| if (rdp->nxtlist) |
| hc = true; |
| } |
| if (all_lazy) |
| *all_lazy = al; |
| return hc; |
| } |
| |
| /* |
| * Helper function for _rcu_barrier() tracing. If tracing is disabled, |
| * the compiler is expected to optimize this away. |
| */ |
| static void _rcu_barrier_trace(struct rcu_state *rsp, char *s, |
| int cpu, unsigned long done) |
| { |
| trace_rcu_barrier(rsp->name, s, cpu, |
| atomic_read(&rsp->barrier_cpu_count), done); |
| } |
| |
| /* |
| * RCU callback function for _rcu_barrier(). If we are last, wake |
| * up the task executing _rcu_barrier(). |
| */ |
| static void rcu_barrier_callback(struct rcu_head *rhp) |
| { |
| struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); |
| struct rcu_state *rsp = rdp->rsp; |
| |
| if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { |
| _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done); |
| complete(&rsp->barrier_completion); |
| } else { |
| _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done); |
| } |
| } |
| |
| /* |
| * Called with preemption disabled, and from cross-cpu IRQ context. |
| */ |
| static void rcu_barrier_func(void *type) |
| { |
| struct rcu_state *rsp = type; |
| struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); |
| |
| _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done); |
| atomic_inc(&rsp->barrier_cpu_count); |
| rsp->call(&rdp->barrier_head, rcu_barrier_callback); |
| } |
| |
| /* |
| * Orchestrate the specified type of RCU barrier, waiting for all |
| * RCU callbacks of the specified type to complete. |
| */ |
| static void _rcu_barrier(struct rcu_state *rsp) |
| { |
| int cpu; |
| struct rcu_data *rdp; |
| unsigned long snap = ACCESS_ONCE(rsp->n_barrier_done); |
| unsigned long snap_done; |
| |
| _rcu_barrier_trace(rsp, "Begin", -1, snap); |
| |
| /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
| mutex_lock(&rsp->barrier_mutex); |
| |
| /* |
| * Ensure that all prior references, including to ->n_barrier_done, |
| * are ordered before the _rcu_barrier() machinery. |
| */ |
| smp_mb(); /* See above block comment. */ |
| |
| /* |
| * Recheck ->n_barrier_done to see if others did our work for us. |
| * This means checking ->n_barrier_done for an even-to-odd-to-even |
| * transition. The "if" expression below therefore rounds the old |
| * value up to the next even number and adds two before comparing. |
| */ |
| snap_done = ACCESS_ONCE(rsp->n_barrier_done); |
| _rcu_barrier_trace(rsp, "Check", -1, snap_done); |
| if (ULONG_CMP_GE(snap_done, ((snap + 1) & ~0x1) + 2)) { |
| _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done); |
| smp_mb(); /* caller's subsequent code after above check. */ |
| mutex_unlock(&rsp->barrier_mutex); |
| return; |
| } |
| |
| /* |
| * Increment ->n_barrier_done to avoid duplicate work. Use |
| * ACCESS_ONCE() to prevent the compiler from speculating |
| * the increment to precede the early-exit check. |
| */ |
| ACCESS_ONCE(rsp->n_barrier_done)++; |
| WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1); |
| _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done); |
| smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */ |
| |
| /* |
| * Initialize the count to one rather than to zero in order to |
| * avoid a too-soon return to zero in case of a short grace period |
| * (or preemption of this task). Exclude CPU-hotplug operations |
| * to ensure that no offline CPU has callbacks queued. |
| */ |
| init_completion(&rsp->barrier_completion); |
| atomic_set(&rsp->barrier_cpu_count, 1); |
| get_online_cpus(); |
| |
| /* |
| * Force each CPU with callbacks to register a new callback. |
| * When that callback is invoked, we will know that all of the |
| * corresponding CPU's preceding callbacks have been invoked. |
| */ |
| for_each_possible_cpu(cpu) { |
| if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu)) |
| continue; |
| rdp = per_cpu_ptr(rsp->rda, cpu); |
| if (rcu_is_nocb_cpu(cpu)) { |
| _rcu_barrier_trace(rsp, "OnlineNoCB", cpu, |
| rsp->n_barrier_done); |
| atomic_inc(&rsp->barrier_cpu_count); |
| __call_rcu(&rdp->barrier_head, rcu_barrier_callback, |
| rsp, cpu, 0); |
| } else if (ACCESS_ONCE(rdp->qlen)) { |
| _rcu_barrier_trace(rsp, "OnlineQ", cpu, |
| rsp->n_barrier_done); |
| smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); |
| } else { |
| _rcu_barrier_trace(rsp, "OnlineNQ", cpu, |
| rsp->n_barrier_done); |
| } |
| } |
| put_online_cpus(); |
| |
| /* |
| * Now that we have an rcu_barrier_callback() callback on each |
| * CPU, and thus each counted, remove the initial count. |
| */ |
| if (atomic_dec_and_test(&rsp->barrier_cpu_count)) |
| complete(&rsp->barrier_completion); |
| |
| /* Increment ->n_barrier_done to prevent duplicate work. */ |
| smp_mb(); /* Keep increment after above mechanism. */ |
| ACCESS_ONCE(rsp->n_barrier_done)++; |
| WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0); |
| _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done); |
| smp_mb(); /* Keep increment before caller's subsequent code. */ |
| |
| /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ |
| wait_for_completion(&rsp->barrier_completion); |
| |
| /* Other rcu_barrier() invocations can now safely proceed. */ |
| mutex_unlock(&rsp->barrier_mutex); |
| } |
| |
| /** |
| * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. |
| */ |
| void rcu_barrier_bh(void) |
| { |
| _rcu_barrier(&rcu_bh_state); |
| } |
| EXPORT_SYMBOL_GPL(rcu_barrier_bh); |
| |
| /** |
| * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. |
| */ |
| void rcu_barrier_sched(void) |
| { |
| _rcu_barrier(&rcu_sched_state); |
| } |
| EXPORT_SYMBOL_GPL(rcu_barrier_sched); |
| |
| /* |
| * Do boot-time initialization of a CPU's per-CPU RCU data. |
| */ |
| static void __init |
| rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) |
| { |
| unsigned long flags; |
| struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| /* Set up local state, ensuring consistent view of global state. */ |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
| init_callback_list(rdp); |
| rdp->qlen_lazy = 0; |
| ACCESS_ONCE(rdp->qlen) = 0; |
| rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
| WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); |
| WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); |
| rdp->cpu = cpu; |
| rdp->rsp = rsp; |
| rcu_boot_init_nocb_percpu_data(rdp); |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| } |
| |
| /* |
| * Initialize a CPU's per-CPU RCU data. Note that only one online or |
| * offline event can be happening at a given time. Note also that we |
| * can accept some slop in the rsp->completed access due to the fact |
| * that this CPU cannot possibly have any RCU callbacks in flight yet. |
| */ |
| static void __cpuinit |
| rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) |
| { |
| unsigned long flags; |
| unsigned long mask; |
| struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
| struct rcu_node *rnp = rcu_get_root(rsp); |
| |
| /* Exclude new grace periods. */ |
| mutex_lock(&rsp->onoff_mutex); |
| |
| /* Set up local state, ensuring consistent view of global state. */ |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| rdp->beenonline = 1; /* We have now been online. */ |
| rdp->preemptible = preemptible; |
| rdp->qlen_last_fqs_check = 0; |
| rdp->n_force_qs_snap = rsp->n_force_qs; |
| rdp->blimit = blimit; |
| init_callback_list(rdp); /* Re-enable callbacks on this CPU. */ |
| rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
| atomic_set(&rdp->dynticks->dynticks, |
| (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); |
| raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| |
| /* Add CPU to rcu_node bitmasks. */ |
| rnp = rdp->mynode; |
| mask = rdp->grpmask; |
| do { |
| /* Exclude any attempts to start a new GP on small systems. */ |
| raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| rnp->qsmaskinit |= mask; |
| mask = rnp->grpmask; |
| if (rnp == rdp->mynode) { |
| /* |
| * If there is a grace period in progress, we will |
| * set up to wait for it next time we run the |
| * RCU core code. |
| */ |
| rdp->gpnum = rnp->completed; |
| rdp->completed = rnp->completed; |
| rdp->passed_quiesce = 0; |
| rdp->qs_pending = 0; |
| trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl"); |
| } |
| raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
| rnp = rnp->parent; |
| } while (rnp != NULL && !(rnp->qsmaskinit & mask)); |
| local_irq_restore(flags); |
| |
| mutex_unlock(&rsp->onoff_mutex); |
| } |
| |
| static void __cpuinit rcu_prepare_cpu(int cpu) |
| { |
| struct rcu_state *rsp; |
| |
| for_each_rcu_flavor(rsp) |
| rcu_init_percpu_data(cpu, rsp, |
| strcmp(rsp->name, "rcu_preempt") == 0); |
| } |
| |
| /* |
| * Handle CPU online/offline notification events. |
| */ |
| static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
| unsigned long action, void *hcpu) |
| { |
| long cpu = (long)hcpu; |
| struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
| struct rcu_node *rnp = rdp->mynode; |
| struct rcu_state *rsp; |
| |
| trace_rcu_utilization("Start CPU hotplug"); |
| switch (action) { |
| case CPU_UP_PREPARE: |
| case CPU_UP_PREPARE_FROZEN: |
| rcu_prepare_cpu(cpu); |
| rcu_prepare_kthreads(cpu); |
| break; |
| case CPU_ONLINE: |
| case CPU_DOWN_FAILED: |
| rcu_boost_kthread_setaffinity(rnp, -1); |
| break; |
| case CPU_DOWN_PREPARE: |
| rcu_boost_kthread_setaffinity(rnp, cpu); |
| break; |
| case CPU_DYING: |
| case CPU_DYING_FROZEN: |
| for_each_rcu_flavor(rsp) |
| rcu_cleanup_dying_cpu(rsp); |
| break; |
| case CPU_DEAD: |
| case CPU_DEAD_FROZEN: |
| case CPU_UP_CANCELED: |
| case CPU_UP_CANCELED_FROZEN: |
| for_each_rcu_flavor(rsp) |
| rcu_cleanup_dead_cpu(cpu, rsp); |
| break; |
| default: |
| break; |
| } |
| trace_rcu_utilization("End CPU hotplug"); |
| return NOTIFY_OK; |
| } |
| |
| /* |
| * Spawn the kthread that handles this RCU flavor's grace periods. |
| */ |
| static int __init rcu_spawn_gp_kthread(void) |
| { |
| unsigned long flags; |
| struct rcu_node *rnp; |
| struct rcu_state *rsp; |
| struct task_struct *t; |
| |
| for_each_rcu_flavor(rsp) { |
| t = kthread_run(rcu_gp_kthread, rsp, rsp->name); |
| BUG_ON(IS_ERR(t)); |
| rnp = rcu_get_root(rsp); |
| raw_spin_lock_irqsave(&rnp->lock, flags); |
| rsp->gp_kthread = t; |
| raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| rcu_spawn_nocb_kthreads(rsp); |
| } |
| return 0; |
| } |
| early_initcall(rcu_spawn_gp_kthread); |
| |
| /* |
| * This function is invoked towards the end of the scheduler's initialization |
| * process. Before this is called, the idle task might contain |
| * RCU read-side critical sections (during which time, this idle |
| * task is booting the system). After this function is called, the |
| * idle tasks are prohibited from containing RCU read-side critical |
| * sections. This function also enables RCU lockdep checking. |
| */ |
| void rcu_scheduler_starting(void) |
| { |
| WARN_ON(num_online_cpus() != 1); |
| WARN_ON(nr_context_switches() > 0); |
| rcu_scheduler_active = 1; |
| } |
| |
| /* |
| * Compute the per-level fanout, either using the exact fanout specified |
| * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. |
| */ |
| #ifdef CONFIG_RCU_FANOUT_EXACT |
| static void __init rcu_init_levelspread(struct rcu_state *rsp) |
| { |
| int i; |
| |
| for (i = rcu_num_lvls - 1; i > 0; i--) |
| rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
| rsp->levelspread[0] = rcu_fanout_leaf; |
| } |
| #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ |
| static void __init rcu_init_levelspread(struct rcu_state *rsp) |
| { |
| int ccur; |
| int cprv; |
| int i; |
| |
| cprv = nr_cpu_ids; |
| for (i = rcu_num_lvls - 1; i >= 0; i--) { |
| ccur = rsp->levelcnt[i]; |
| rsp->levelspread[i] = (cprv + ccur - 1) / ccur; |
| cprv = ccur; |
| } |
| } |
| #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ |
| |
| /* |
| * Helper function for rcu_init() that initializes one rcu_state structure. |
| */ |
| static void __init rcu_init_one(struct rcu_state *rsp, |
| struct rcu_data __percpu *rda) |
| { |
| static char *buf[] = { "rcu_node_0", |
| "rcu_node_1", |
| "rcu_node_2", |
| "rcu_node_3" }; /* Match MAX_RCU_LVLS */ |
| static char *fqs[] = { "rcu_node_fqs_0", |
| "rcu_node_fqs_1", |
| "rcu_node_fqs_2", |
| "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */ |
| int cpustride = 1; |
| int i; |
| int j; |
| struct rcu_node *rnp; |
| |
| BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
| |
| /* Silence gcc 4.8 warning about array index out of range. */ |
| if (rcu_num_lvls > RCU_NUM_LVLS) |
| panic("rcu_init_one: rcu_num_lvls overflow"); |
| |
| /* Initialize the level-tracking arrays. */ |
| |
| for (i = 0; i < rcu_num_lvls; i++) |
| rsp->levelcnt[i] = num_rcu_lvl[i]; |
| for (i = 1; i < rcu_num_lvls; i++) |
| rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
| rcu_init_levelspread(rsp); |
| |
| /* Initialize the elements themselves, starting from the leaves. */ |
| |
| for (i = rcu_num_lvls - 1; i >= 0; i--) { |
| cpustride *= rsp->levelspread[i]; |
| rnp = rsp->level[i]; |
| for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { |
| raw_spin_lock_init(&rnp->lock); |
| lockdep_set_class_and_name(&rnp->lock, |
| &rcu_node_class[i], buf[i]); |
| raw_spin_lock_init(&rnp->fqslock); |
| lockdep_set_class_and_name(&rnp->fqslock, |
| &rcu_fqs_class[i], fqs[i]); |
| rnp->gpnum = rsp->gpnum; |
| rnp->completed = rsp->completed; |
| rnp->qsmask = 0; |
| rnp->qsmaskinit = 0; |
| rnp->grplo = j * cpustride; |
| rnp->grphi = (j + 1) * cpustride - 1; |
| if (rnp->grphi >= NR_CPUS) |
| rnp->grphi = NR_CPUS - 1; |
| if (i == 0) { |
| rnp->grpnum = 0; |
| rnp->grpmask = 0; |
| rnp->parent = NULL; |
| } else { |
| rnp->grpnum = j % rsp->levelspread[i - 1]; |
| rnp->grpmask = 1UL << rnp->grpnum; |
| rnp->parent = rsp->level[i - 1] + |
| j / rsp->levelspread[i - 1]; |
| } |
| rnp->level = i; |
|