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

[Daniel P. Berrangé]

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 ?

> 
> 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
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