[libvirt PATCH 6/7] virMutex*: Warn on error

[Daniel P. Berrangé]

On Thu, Aug 05, 2021 at 02:58:03PM +0100, Daniel P. Berrangé wrote:
> On Thu, Aug 05, 2021 at 03:33:57PM +0200, Tim Wiederhake wrote:
> > On Thu, 2021-08-05 at 14:24 +0100, Daniel P. Berrangé wrote:
> > > On Thu, Aug 05, 2021 at 03:08:50PM +0200, Tim Wiederhake wrote:
> > > > `pthread_mutex_destroy`, `pthread_mutex_lock` and
> > > > `pthread_mutex_unlock`
> > > > return an error code that is currently ignored.
> > > > 
> > > > Add debug information if one of these operations failed, e.g. when
> > > > there
> > > > is an attempt to destroy a still locked mutex or unlock and already
> > > > unlocked mutex.
> > > 
> > > We ignore the errors because in practice we found impls don't return
> > > any error code when using PTHREAD_MUTEX_NORMAL - it would require use
> > > of PTHREAD_MUTEX_ERRORCHECK.
> > > 
> > > Did you actually see errors returned for real ?
> > 
> > Yes. Please note that I apprently copy-pasted the wrong link in the
> > cover letter. The pipeline for this series is correct
> > (https://gitlab.com/twiederh/libvirt/-/pipelines/348505233), the
> > pipeline for only patches 5, 6, 7 that demonstrate the non-zero return
> > values of pthread_mutex_{lock,unlock,destroy} is here:
> > 
> > https://gitlab.com/twiederh/libvirt/-/pipelines/348505770
> 
> All that's showing is
> 
>   (killed by signal 6 SIGABRT)
> 
> where's the VIR_WARN output that ought to have ended up on stderr
> from the failed test before aborting ?

Ok, so the VIR_WARN output is getting squelched by the tests
somewhere, as its missing when i run locally too.

If I add a test that does

    virMutex m;
    ignore_value(virMutexInit(&m));

    virMutexUnlock(&m);

then I get no warnings with this patch, nor abort with the next
patch.

It only triggers with PTHREAD_MUTEX_ERRORCHECK

The pthread_mutex_destroy call is the only one that I see
returning errors with PTHREAD_MUTEX_NORMAL. So I don't think
there's benefit to adding the code to lock/unlock paths.


Regards,
Daniel
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