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Re: [Qemu-devel] [PATCH] test-replication: Lock AioContext around blk_un
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] [PATCH] test-replication: Lock AioContext around blk_unref() |
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Date: |
Mon, 1 Oct 2018 18:13:39 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 |
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()).