On 5/27/2022 12:52 AM, Petro Karashchenko wrote:
Hi,
Ok. That makes sense. But there is a strane code in sem_wait:
if (enter_cancellation_point())
{
#ifdef CONFIG_CANCELLATION_POINTS
/* If there is a pending cancellation, then do not perform
* the wait. Exit now with ECANCELED.
*/
errcode = ECANCELED;
goto errout_with_cancelpt;
#endif
}
This code in conjunction with "while ((ret = _SEM_WAIT(sem)) < 0)" seems to
be a pure "deadlock" (endless loop) in case if _SEM_WAIT is defined to
sem_wait. Or am I missing something?
This is of course when sem_wait is called while the task entered the
cancellation point already.
Best regards,
Petro
"while ((ret = _SEM_WAIT(sem)) < 0)" is not an endless loop.
ECANCEL is handled just like EINTR: For EINTR, when the signal is
received, _SEM_WAIT wakes up and returns -EINTR. If _SEM_WAIT is called
again, it does not remember that the thread was signaled; it does not
return -EINTR again but behaves normally and waits for the semaphore.
ECANCEL works the same: When a thread is canceled, _SEM_WAIT wakes up
and return -ECANCELED. If _SEM_WAIT is called it again, it does not
remember that the thread was canceled; it does not return -ECANCELED
again but behaves normally and waits for the semaphore.
So there is no infinite loop.
