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

[Tim Wiederhake]

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

Regards,
Tim

> 
> > Signed-off-by: Tim Wiederhake <twiederh at redhat.com>
> > ---
> >  src/util/virthread.c | 15 ++++++++++++---
> >  1 file changed, 12 insertions(+), 3 deletions(-)
> > 
> > diff --git a/src/util/virthread.c b/src/util/virthread.c
> > index e89c1a09fb..f64dbee9e9 100644
> > --- a/src/util/virthread.c
> > +++ b/src/util/virthread.c
> > @@ -35,7 +35,10 @@
> >  
> >  #include "viralloc.h"
> >  #include "virthreadjob.h"
> > +#include "virlog.h"
> >  
> > +#define VIR_FROM_THIS VIR_FROM_THREAD
> > +VIR_LOG_INIT("util.thread");
> >  
> >  int virOnce(virOnceControl *once, virOnceFunc init)
> >  {
> > @@ -83,17 +86,23 @@ int virMutexInitRecursive(virMutex *m)
> >  
> >  void virMutexDestroy(virMutex *m)
> >  {
> > -    pthread_mutex_destroy(&m->lock);
> > +    if (pthread_mutex_destroy(&m->lock)) {
> > +        VIR_WARN("Failed to destroy mutex=%p", m);
> > +    }
> >  }
> >  
> >  void virMutexLock(virMutex *m)
> >  {
> > -    pthread_mutex_lock(&m->lock);
> > +    if (pthread_mutex_lock(&m->lock)) {
> > +        VIR_WARN("Failed to lock mutex=%p", m);
> > +    }
> >  }
> >  
> >  void virMutexUnlock(virMutex *m)
> >  {
> > -    pthread_mutex_unlock(&m->lock);
> > +    if (pthread_mutex_unlock(&m->lock)) {
> > +        VIR_WARN("Failed to unlock mutex=%p", m);
> > +    }
> >  }
> >  
> >  
> > -- 
> > 2.31.1
> > 
> 
> Regards,
> Daniel