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score: PR2140: Fix _Thread_queue_Process_timeout()

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The _Thread_queue_Process_timeout() operation had several race
conditions in the event of nested interrupts.  Protect the critical
sections via disabled interrupts.
This commit is contained in:
Sebastian Huber
2013-08-26 10:02:53 +02:00
parent 215ccceed3
commit f8f1bdad27
1 changed files with 37 additions and 8 deletions
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cpukit/score/src/threadqprocesstimeout.c
+37 -8
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@@ -25,7 +25,8 @@ void _Thread_queue_Process_timeout(
Thread_Control *the_thread
)
{
Thread_queue_Control *the_thread_queue = the_thread->Wait.queue;
Thread_queue_Control *the_thread_queue;
ISR_Level level;
/*
* If the_thread_queue is not synchronized, then it is either
@@ -39,15 +40,43 @@ void _Thread_queue_Process_timeout(
* a timeout is not allowed to occur.
*/
if ( the_thread_queue->sync_state != THREAD_BLOCKING_OPERATION_SYNCHRONIZED &&
_Thread_Is_executing( the_thread ) ) {
if ( the_thread_queue->sync_state != THREAD_BLOCKING_OPERATION_SATISFIED ) {
the_thread->Wait.return_code = the_thread->Wait.queue->timeout_status;
the_thread_queue->sync_state = THREAD_BLOCKING_OPERATION_TIMEOUT;
_ISR_Disable( level );
the_thread_queue = the_thread->Wait.queue;
if ( the_thread_queue != NULL ) {
if ( the_thread_queue->sync_state != THREAD_BLOCKING_OPERATION_SYNCHRONIZED &&
_Thread_Is_executing( the_thread ) ) {
if ( the_thread_queue->sync_state != THREAD_BLOCKING_OPERATION_SATISFIED ) {
the_thread->Wait.return_code = the_thread_queue->timeout_status;
the_thread_queue->sync_state = THREAD_BLOCKING_OPERATION_TIMEOUT;
}
_ISR_Enable( level );
} else {
bool we_did_it;
_ISR_Enable( level );
/*
* After we enable interrupts here, a lot may happen in the meantime,
* e.g. nested interrupts may release the resource that times out here.
* So we enter _Thread_queue_Extract() speculatively. Inside this
* function we check the actual status under ISR disable protection.
* This ensures that exactly one executing context performs the extract
* operation (other parties may call _Thread_queue_Dequeue()). If this
* context won, then we have a timeout.
*
* We can use the_thread_queue pointer here even if
* the_thread->Wait.queue is already set to NULL since the extract
* operation will only use the thread queue discipline to select the
* right extract operation. The timeout status is set during thread
* queue initialization.
*/
we_did_it = _Thread_queue_Extract( the_thread_queue, the_thread );
if ( we_did_it ) {
the_thread->Wait.return_code = the_thread_queue->timeout_status;
}
}
} else {
the_thread->Wait.return_code = the_thread->Wait.queue->timeout_status;
_Thread_queue_Extract( the_thread->Wait.queue, the_thread );
_ISR_Enable( level );
}
}