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Re: [Qemu-devel] [PATCH v2] main-loop: fix qemu_notify_event for aio_not

From: Stefan Hajnoczi
Subject: Re: [Qemu-devel] [PATCH v2] main-loop: fix qemu_notify_event for aio_notify optimization
Date: Mon, 27 Jul 2015 11:20:16 +0100
User-agent: Mutt/1.5.23 (2014-03-12)

On Fri, Jul 24, 2015 at 01:42:55PM +0200, Paolo Bonzini wrote:
> aio_notify can be optimized away, and in fact almost always will.  However,
> qemu_notify_event is used in places where this is incorrect---most notably,
> when handling SIGTERM.  When aio_notify is optimized away, it is possible that
> QEMU enters a blocking ppoll immediately afterwards and stays there, without
> reaching main_loop_should_exit().
> Fix this by using a bottom half.  The bottom half can be optimized too, but
> scheduling it is enough for the ppoll not to block.  The hang is thus avoided.
> Reported-by: Peter Maydell <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  main-loop.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <address@hidden>

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