Re: Breaking out of pthread_mutex_lock

[Gilles Carry <Gilles.Carry@bull.net>]

Hello Darren,

In futex_lock_pi(futex.c) when ERESTARTNOINTR which make the syscall to 
be reexecuted whatever comes after the sighandler ends.

One trick you can try (I've not tested it!) is use 
pthread_timedlock(mutex, abstime) and in sighandler, set abstime values 
to cause timeout. Since futex_lock_pi reads the time struct at each 
call, it will exit on timeout at reexecution.
Worth trying.

Gilles.

Darren Hart wrote:
> I find I need to be able to break out of the blocked state while waiting
> to acquire a pthread_mutex.  I'm using PI mutexes and want to continue
> to do so.  As I understand it, I can't use a signal to break out of the
> lock as the man pages states:
> 
> "If a signal is delivered to a thread waiting for a mutex,  upon  return
> from  the  signal handler the thread shall resume waiting for the mutex
> as if it was not interrupted."
> 
> and that pthread_mutex_lock will not return EINTR.  I had considered
> using cond variables, but I don't think they will provide the same PI
> behavior (since the threads are not blocked on the mutex while awaiting
> the pthread_cond_signal - right?).
> 
> I'm sure I'm not the first to want to do this, does anyone know of a
> common best practice for accomplishing such a thing?
> 

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