#4679: Use priority inheritance for thread join
-----------------------------+------------------------------
Reporter: Sebastian Huber | Owner: Sebastian Huber
Type: enhancement | Status: assigned
Priority: normal | Milestone: 6.1
Component: score | Version: 6
Severity: normal | Resolution:
Keywords: | Blocked By:
Blocking: |
-----------------------------+------------------------------
Description changed by Sebastian Huber:
Old description:
> Threads may join the thread termination of another thread using the
> `pthread_join()` or `rtems_task_delete()` directives. Currently, the
> thread join operation uses a special case priority boosting mechanism:
> {{{#!c
> static void _Thread_Raise_real_priority(
> Thread_Control *the_thread,
> Priority_Control priority
> )
> {
> Thread_queue_Context queue_context;
>
> _Thread_queue_Context_initialize( &queue_context );
> _Thread_queue_Context_clear_priority_updates( &queue_context );
> _Thread_Wait_acquire( the_thread, &queue_context );
>
> if ( priority < the_thread->Real_priority.priority ) {
> _Thread_Priority_change(
> the_thread,
> &the_thread->Real_priority,
> priority,
> PRIORITY_GROUP_LAST,
> &queue_context
> );
> }
>
> _Thread_Wait_release( the_thread, &queue_context );
> _Thread_Priority_update( &queue_context );
> }
> }}}
> The problem is that this approach is not transitive, it does not account
> for priority adjustments of the calling task while waiting for the join,
> clustered scheduling is not supported, and deadlocks are not detected.
> All these problems are fixed by using a priority inheritance thread queue
> for the join operation.
New description:
Threads may join the thread termination of another thread using the
`pthread_join()` or `rtems_task_delete()` directives. Currently, the
thread cancel operation uses a special case priority boosting mechanism:
{{{#!c
static void _Thread_Raise_real_priority(
Thread_Control *the_thread,
Priority_Control priority
)
{
Thread_queue_Context queue_context;
_Thread_queue_Context_initialize( &queue_context );
_Thread_queue_Context_clear_priority_updates( &queue_context );
_Thread_Wait_acquire( the_thread, &queue_context );
if ( priority < the_thread->Real_priority.priority ) {
_Thread_Priority_change(
the_thread,
&the_thread->Real_priority,
priority,
PRIORITY_GROUP_LAST,
&queue_context
);
}
_Thread_Wait_release( the_thread, &queue_context );
_Thread_Priority_update( &queue_context );
}
}}}
The problem is that this approach is not transitive, it does not account
for priority adjustments of the calling task while waiting for the join,
clustered scheduling is not supported, and deadlocks are not detected. All
these problems are fixed by using a priority inheritance thread queue for
the join operation.
--
--
Ticket URL: <http://devel.rtems.org/ticket/4679#comment:1>
RTEMS Project <http://www.rtems.org/>
RTEMS Project
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