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authorSebastian Huber <sebastian.huber@embedded-brains.de>2013-08-23 12:19:13 +0200
committerSebastian Huber <sebastian.huber@embedded-brains.de>2013-08-26 10:02:53 +0200
commitf8f1bdad2770c280ec019cf8f048346451a2e0ea (patch)
tree4bf06444e286618bc9477dd3d401256692ae0fea
parent215ccceed3938c2d90a5e44493ac3d016230a502 (diff)
downloadrtems-f8f1bdad2770c280ec019cf8f048346451a2e0ea.tar.bz2
score: PR2140: Fix _Thread_queue_Process_timeout()
The _Thread_queue_Process_timeout() operation had several race conditions in the event of nested interrupts. Protect the critical sections via disabled interrupts.
-rw-r--r--cpukit/score/src/threadqprocesstimeout.c45
1 files changed, 37 insertions, 8 deletions
diff --git a/cpukit/score/src/threadqprocesstimeout.c b/cpukit/score/src/threadqprocesstimeout.c
index 6aaf445d33..7b58edbe7e 100644
--- a/cpukit/score/src/threadqprocesstimeout.c
+++ b/cpukit/score/src/threadqprocesstimeout.c
@@ -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 );
}
}