From: Paolo Bonzini <pbonzini@redhat.com>
To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-block@nongnu.org, mreitz@redhat.com,
peter.maydell@linaro.org, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] test-replication: Lock AioContext around blk_unref()
Date: Mon, 1 Oct 2018 18:13:39 +0200 [thread overview]
Message-ID: <c038c3cd-2dc6-c32c-0a20-1256868dffc2@redhat.com> (raw)
In-Reply-To: <20181001160348.GB4445@localhost.localdomain>
On 01/10/2018 18:03, Kevin Wolf wrote:
>> Given the backtrace, I think bdrv_close should be taking the AioContext
>> lock instead of blockdev_close_all_bdrv_states.
> Conversely, that would mean that calling bdrv_unref() with the
> AioContext lock held is a bug (because close callbacks can involve
> AIO_WAIT_WHILE()). I'm not sure if that's very practical.
What if bdrv_unref_child dropped the lock?
Perhaps it's simpler to just kill the lock though, if
bdrv_set_aio_context can be figured out.
Paolo
> Of course, there will probably be a lot of callers to fix either way
> after we define whether to hold the lock for bdrv_unref() or not. Either
> you need to add locking to the places where it's missing or you need to
> drop the locks in all other places.
>
> I was leaning towards requiring the lock for bdrv_unref() (and
> therefore blk_unref()).
prev parent reply other threads:[~2018-10-01 16:13 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-01 14:32 [Qemu-devel] [PATCH] test-replication: Lock AioContext around blk_unref() Kevin Wolf
2018-10-01 15:40 ` Paolo Bonzini
2018-10-01 16:03 ` Kevin Wolf
2018-10-01 16:13 ` Paolo Bonzini [this message]
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