mq_receive/send: Return appropriate errnos and stop waiting if signal received.

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@164 42af7a65-404d-4744-a932-0658087f49c3

sched/sem_wait.c

@@ -156,11 +156,13 @@ int sem_wait(sem_t *sem)
 
           /* Add the TCB to the prioritized semaphore wait queue */
 
+          *get_errno_ptr() = 0;
           up_block_task(rtcb, TSTATE_WAIT_SEM);
 
           /* When we resume at this point, either (1) the semaphore has been
            * assigned to this thread of execution, or (2) the semaphore wait
-           * has been interrupted by a signal.
+           * has been interrupted by a signal.  We can detect the latter case
+           * be examining the errno value.
            */
 
           if (*get_errno_ptr() != EINTR)