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| <h4 class="subsection">27.1.3 Thread groups</h4> |
| |
| <p><span class="sc">gdb</span> may be used to debug several processes at the same time. |
| On some platfroms, <span class="sc">gdb</span> may support debugging of several |
| hardware systems, each one having several cores with several different |
| processes running on each core. This section describes the MI |
| mechanism to support such debugging scenarios. |
| |
| <p>The key observation is that regardless of the structure of the |
| target, MI can have a global list of threads, because most commands that |
| accept the ‘<samp><span class="samp">--thread</span></samp>’ option do not need to know what process that |
| thread belongs to. Therefore, it is not necessary to introduce |
| neither additional ‘<samp><span class="samp">--process</span></samp>’ option, nor an notion of the |
| current process in the MI interface. The only strictly new feature |
| that is required is the ability to find how the threads are grouped |
| into processes. |
| |
| <p>To allow the user to discover such grouping, and to support arbitrary |
| hierarchy of machines/cores/processes, MI introduces the concept of a |
| <dfn>thread group</dfn>. Thread group is a collection of threads and other |
| thread groups. A thread group always has a string identifier, a type, |
| and may have additional attributes specific to the type. A new |
| command, <code>-list-thread-groups</code>, returns the list of top-level |
| thread groups, which correspond to processes that <span class="sc">gdb</span> is |
| debugging at the moment. By passing an identifier of a thread group |
| to the <code>-list-thread-groups</code> command, it is possible to obtain |
| the members of specific thread group. |
| |
| <p>To allow the user to easily discover processes, and other objects, he |
| wishes to debug, a concept of <dfn>available thread group</dfn> is |
| introduced. Available thread group is an thread group that |
| <span class="sc">gdb</span> is not debugging, but that can be attached to, using the |
| <code>-target-attach</code> command. The list of available top-level thread |
| groups can be obtained using ‘<samp><span class="samp">-list-thread-groups --available</span></samp>’. |
| In general, the content of a thread group may be only retrieved only |
| after attaching to that thread group. |
| |
| <p>Thread groups are related to inferiors (see <a href="Inferiors-and-Programs.html#Inferiors-and-Programs">Inferiors and Programs</a>). Each inferior corresponds to a thread group of a special |
| type ‘<samp><span class="samp">process</span></samp>’, and some additional operations are permitted on |
| such thread groups. |
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