[m-rev.] for review: Handle sem_wait, sem_timedwait being interrupted by signal handlers.

[Julien Fischer]

Hi Peter,

On Wed, 5 Jul 2017, Peter Wang wrote:

> sem_wait or sem_timedwait may be interrupted by signal handlers and
> return an error. We must retry the call if errno is set to EINTR.
>
> library/thread.m:
>    Retry MR_SEM_WAIT if interrupted by a signal handler in
>    ML_create_exclusive_thread.
>
>    Call MR_fatal_error if MR_SEM_WAIT fails for any other reason.
>    The only other documented error code is EINVAL if the semaphore is
>    invalid; that should not happen.
>
> runtime/mercury_context.c:
>    Retry MR_SEM_WAIT if interrupted by a signal handler in
>    MR_shutdown_ws_engines.
>
> runtime/mercury_thread.h:
>    Add the macro MR_SEM_IS_EINTR for checking if errno == EINTR
>    after calling MR_SEM_WAIT or MR_SEM_TIMED_WAIT.

That looks fine (apart from the issue you've already fixed).

Julien.