There is one issue we have to be careful about: pthread
_mutex_timedlock(): It needs the signal in order to wake up and return
from the wait. pthread_mutex_lock() just calls pthread_mutex_timedlock()
with and time value of NULL. So it is this NULL argument that is passed
must cause different behaviors: Non-NULL: interruptible and NULL:
noninterruptible.
Actually, there is a problem with that. The above approach would not
work because it would break cancellation of threads via signals.
nxsem_wait_uninterruptible() cannot be used in this case because it
ignores cancallations:
include/nuttx/semaphore.h:
544 static inline int nxsem_wait_uninterruptible(FAR sem_t *sem)
545 {
546 int ret;
547
548 do
549 {
550 /* Take the semaphore (perhaps waiting) */
551
552 ret = nxsem_wait(sem);
553 }
554 while (ret == -EINTR || ret == -ECANCELED);
555
556 return ret;
557 }
-ECANCELED must wake up the thread so that it can die gracefully. If it
continues to loop on nxsem_wait() then cancellation is broken.
