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Date: Mon, 24 Feb 2014 17:48:13 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/2] iothread: stash thread ID away
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: "Shergill, Gurinder" <gurinder.shergill@hp.com>, "Vinod,
	Chegu" <chegu_vinod@hp.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, Luiz Capitulino <lcapitulino@redhat.com>

Il 24/02/2014 16:53, Stefan Hajnoczi ha scritto:
>>> > >+    qemu_cond_destroy(&init_info.init_done_cond);
>>> > >+    qemu_mutex_destroy(&init_info.init_done_lock);
>> >
>> > Destroying the mutex here is racy.  You need to keep it until the
>> > iothread is destroyed.
> I don't think so:
>
> qemu_cond_signal() is called with the mutex held.  Therefore, our
> qemu_cond_wait() followed by qemu_mutex_unlock() will only complete once
> the thread has released the mutex.
>
> The thread will never touch the mutex again so it is safe to destroy it.
> There is no race condition.

Could qemu_mutex_destroy run while the other thread has already released 
the main thread, but before it returns?  As far as I know, the only time 
when it is safe to destroy the "last" synchronization object (in this 
case the mutex is the last, the condvar is not) is after pthread_join.

Paolo