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Date: Tue, 24 Apr 2018 12:53:47 +0800
From: Peter Xu <peterx@redhat.com>
Message-ID: <20180424045347.GB9036@xz-mi>
References: <20180423053927.13715-1-peterx@redhat.com>
	<20180423053927.13715-4-peterx@redhat.com>
	<20180423181107.GB27690@flamenco>
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Subject: Re: [Qemu-devel] [PATCH v4 3/4] QemuMutex: support
 --enable-debug-mutex
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To: "Emilio G. Cota" <cota@braap.org>
Cc: qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, Fam Zheng <famz@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>

On Mon, Apr 23, 2018 at 02:11:07PM -0400, Emilio G. Cota wrote:
> On Mon, Apr 23, 2018 at 13:39:26 +0800, Peter Xu wrote:
> > We have had some tracing tools for mutex but it's not easy to use them
> > for e.g. dead locks.  Let's provide "--enable-debug-mutex" parameter
> > when configure to allow QemuMutex to store the last owner that took
> > specific lock.  It will be easy to use this tool to debug deadlocks
> > since we can directly know who took the lock then as long as we can have
> > a debugger attached to the process.
> > 
> > Signed-off-by: Peter Xu <peterx@redhat.com>
> > ---
> (snip)
> >  static inline void qemu_mutex_pre_unlock(QemuMutex *mutex,
> >                                           const char *file, int line)
> >  {
> > +#ifdef CONFIG_DEBUG_MUTEX
> > +    mutex->file = NULL;
> > +    mutex->line = 0;
> > +#endif
> >      trace_qemu_mutex_unlock(mutex, file, line);
> >  }
> 
> I'd also initialize to NULL/0 the file/line pair at
> qemu_mutex_init time for both posix and win32. Other than that:
> 
> Reviewed-by: Emilio G. Cota <cota@braap.org>

I did the same trick for mutex init in patch 2 & 3 and reposted, while
I picked up your r-b for patch 4 only.  Please have a look.  Thanks,

-- 
Peter Xu