From: Rusty Russell <rusty@rustcorp.com.au>
To: Asias He <asias@redhat.com>,
virtualization@lists.linux-foundation.org,
"Michael S. Tsirkin" <mst@redhat.com>
Cc: kvm@vger.kernel.org
Subject: Re: [PATCH v3] virtio-blk: Fix hot-unplug race in remove method
Date: Mon, 07 May 2012 14:35:28 +0930 [thread overview]
Message-ID: <87obq0eg2v.fsf@rustcorp.com.au> (raw)
In-Reply-To: <1336134124-14744-1-git-send-email-asias@redhat.com>
On Fri, 4 May 2012 20:22:04 +0800, Asias He <asias@redhat.com> wrote:
> If we reset the virtio-blk device before the requests already dispatched
> to the virtio-blk driver from the block layer are finised, we will stuck
> in blk_cleanup_queue() and the remove will fail.
>
> blk_cleanup_queue() calls blk_drain_queue() to drain all requests queued
> before DEAD marking. However it will never success if the device is
> already stopped. We'll have q->in_flight[] > 0, so the drain will not
> finish.
>
> How to reproduce the race:
> 1. hot-plug a virtio-blk device
> 2. keep reading/writing the device in guest
> 3. hot-unplug while the device is busy serving I/O
>
> Test:
> ~1000 rounds of hot-plug/hot-unplug test passed with this patch.
>
> Changes in v3:
> - Drop blk_abort_queue and blk_abort_request
> - Use __blk_end_request_all to complete request dispatched to driver
OK, replaced v2 with this one.
Thanks,
Rusty.
next prev parent reply other threads:[~2012-05-07 5:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-04 12:22 [PATCH v3] virtio-blk: Fix hot-unplug race in remove method Asias He
2012-05-07 5:05 ` Rusty Russell [this message]
-- strict thread matches above, loose matches on Subject: below --
2012-05-04 8:39 Asias He
2012-05-07 5:01 ` Rusty Russell
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