Re: [Qemu-devel] [PATCH] linux-aio: avoid deadlock in nested aio_poll() calls

[Stefan Hajnoczi]

On Mon, Aug 04, 2014 at 04:56:33PM +0100, Stefan Hajnoczi wrote:
> If two Linux AIO request completions are fetched in the same
> io_getevents() call, QEMU will deadlock if request A's callback waits
> for request B to complete using an aio_poll() loop.  This was reported
> to happen with the mirror blockjob.
> 
> This patch moves completion processing into a BH and makes it resumable.
> Nested event loops can resume completion processing so that request B
> will complete and the deadlock will not occur.
> 
> Cc: Kevin Wolf <address@hidden>
> Cc: Paolo Bonzini <address@hidden>
> Cc: Ming Lei <address@hidden>
> Cc: Marcin Gibuła <address@hidden>
> Reported-by: Marcin Gibuła <address@hidden>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
>  block/linux-aio.c | 71 
> ++++++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 55 insertions(+), 16 deletions(-)

Applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan

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