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Re: [Qemu-devel] another locking issue in current dataplane code?
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From: |
Stefan Hajnoczi |
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Subject: |
Re: [Qemu-devel] another locking issue in current dataplane code? |
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Date: |
Tue, 8 Jul 2014 17:59:56 +0200 |
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User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Mon, Jul 07, 2014 at 01:58:01PM +0200, Christian Borntraeger wrote:
> Now. If aio_poll never returns, we have a deadlock here.
> To me it looks like, that aio_poll could be called from iothread_run, even if
> there are no outstanding request.
> Opinions?
Christian pointed out that iothread_run() can miss aio_notify() if a
file descriptor becomes readable/writeable at the same time as the
AioContext->notifier. aio_poll() will return true since progress was
made and we are left with a hung QEMU.
I sent Christian an initial patch to fix this but now both threads are
stuck in rfifolock_lock() inside cond wait. That's very strange and
should never happen.
Still trying to figure out what is going on...
Stefan
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