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Date: Thu, 29 Aug 2013 17:37:29 +0200
From: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20130829153729.GA27529@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 2/2] qemu-timer: make
 qemu_timer_mod_ns() and qemu_timer_del() thread-safe
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Ping Fan Liu <pingfank@linux.vnet.ibm.com>, qemu-devel@nongnu.org, Alex Bligh <alex@alex.org.uk>

On Thu, Aug 29, 2013 at 12:00:12PM +0200, Paolo Bonzini wrote:
> Il 27/08/2013 10:23, Stefan Hajnoczi ha scritto:
> >  /* modify the current timer so that it will be fired when current_time
> >     >= expire_time. The corresponding callback will be called. */
> >  void timer_mod_ns(QEMUTimer *ts, int64_t expire_time)
> >  {
> > +    QEMUTimerList *timer_list = ts->timer_list;
> >      QEMUTimer **pt, *t;
> >  
> >      timer_del(ts);
> >  
> >      /* add the timer in the sorted list */
> > -    pt = &ts->timer_list->active_timers;
> > +    qemu_mutex_lock(&timer_list->active_timers_lock);
> > +    pt = &timer_list->active_timers;
> 
> I think deletion and modification of the list should happen without
> releasing the lock in the middle.

Thanks for explaining the race between two timer_mod_ns() calls to me on
IRC.  I have sent a new revision of this series with your fixes included.

Stefan