From: Stefan Hajnoczi <stefanha@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>,
qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [Qemu-devel] [PATCH for-2.1? 2/2] thread-pool: avoid deadlock in nested aio_poll() calls
Date: Tue, 15 Jul 2014 16:37:19 +0200 [thread overview]
Message-ID: <20140715143718.GA19441@stefanha-thinkpad.redhat.com> (raw)
In-Reply-To: <53C3B5C2.7010001@redhat.com>
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On Mon, Jul 14, 2014 at 12:49:38PM +0200, Paolo Bonzini wrote:
> Il 14/07/2014 10:36, Paolo Bonzini ha scritto:
> >
> >
> >to
> >
> > /* In case elem->common.cb() makes a nested aio_poll() call,
> > * next may become invalid as well. Instead of just
> > * restarting the QLIST_FOREACH_SAFE, go through the BH
> > * once more, which also avoids deadlock if element A's
> > * callback waits for element B and both completed at the
> > * same time.
> > */
> > qemu_bh_schedule(pool->completion_bh);
> > elem->common.cb(elem->common.opaque, elem->ret);
> > qemu_aio_release(elem);
>
> This is of course missing here:
>
> break;
Let's keep goto restart so we don't use the BH for each completion
callback. We just need the BH scheduled once to protect against the
deadlock.
Stefan
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next prev parent reply other threads:[~2014-07-15 14:37 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-11 11:20 [Qemu-devel] [PATCH for-2.1? 0/2] thread-pool: avoid fd usage and fix nested aio_poll() deadlock Stefan Hajnoczi
2014-07-11 11:20 ` [Qemu-devel] [PATCH for-2.1? 1/2] thread-pool: avoid per-thread-pool EventNotifier Stefan Hajnoczi
2014-07-11 11:20 ` [Qemu-devel] [PATCH for-2.1? 2/2] thread-pool: avoid deadlock in nested aio_poll() calls Stefan Hajnoczi
2014-07-14 8:36 ` Paolo Bonzini
2014-07-14 10:49 ` Paolo Bonzini
2014-07-15 14:37 ` Stefan Hajnoczi [this message]
2014-07-15 15:21 ` Paolo Bonzini
2014-07-17 12:56 ` Stefan Hajnoczi
2014-07-15 14:23 ` Stefan Hajnoczi
2014-07-11 11:37 ` [Qemu-devel] [PATCH for-2.1? 0/2] thread-pool: avoid fd usage and fix nested aio_poll() deadlock Christian Borntraeger
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