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Re: [Qemu-block] [PATCH v2 2/2] aio: Do aio_notify_accept only during bl
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-block] [PATCH v2 2/2] aio: Do aio_notify_accept only during blocking aio_poll |
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Date: |
Tue, 7 Aug 2018 12:15:08 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
On 07/08/2018 11:16, Fam Zheng wrote:
> main thread IO Thread
> ===============================================================
> bdrv_drained_begin()
> aio_disable_external(ctx)
> aio_poll(ctx, true)
> ctx->notify_me += 2
> ppoll() /* blocked */
> ...
> bdrv_drained_end()
> ...
> aio_notify()
> ...
> bdrv_set_aio_context()
> aio_poll(ctx, false)
> [1] aio_notify_accept(ctx)
> /* Hang! */
Should ppoll() rather be after [1]? Otherwise the new commit message
and patches look great.
> aio_notify() only injects an event when ctx->notify_me is set,
> correspondingly aio_notify_accept() is only useful when ctx->notify_me
> _was_ set.
Very good point.
(Please Cc qemu-stable on the second patch too).
Paolo