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From Yann Ylavic <ylavic....@gmail.com>
Subject Re: 1.6.0 release candidates
Date Tue, 25 Apr 2017 07:55:30 GMT
Hi Rainer,

sorry for the delay.

On Wed, Apr 19, 2017 at 1:36 PM, Rainer Jung <rainer.jung@kippdata.de> wrote:
> The wait_usec loop tying the apr_proc_mutex_timedlock() very often succeeds
> already during the first or second, sometimes the third attempt. But then
> the outer loop "while (i < MAX_ITER)" suddenly starts to fail because the
> inner loop switches behavior and apr_proc_mutex_timedlock() always gets the
> timeout until we stop trying due to wait_usec. Increasing MAX_WAIT_USEC from
> 1 sec to 5 sec didn't help. I have no idea, what the root cause for this
> behavior switching is.

I think what might happen is some pthread_cond_timedwait() spurious
wakeup (which I thought was avoided by counting the number of
waiters), or another possibility is a wakeup with timeout whereas the
cond is simultaneously signaled.

I both cases this could lead to a desynchronization between
proc_mutex_pthread_acquire_ex() and proc_mutex_pthread_release().

The attached patch prevents this by looping on
pthread_cond_[timed]wait() until the condition is satisfied.
Would you please try it?


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