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

[Daniel P. Berrangé]

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 ?


> > > 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
> 
> 

Regards,
Daniel
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