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References: <20180913125217.23173-1-kwolf@redhat.com>
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From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <908e08a4-a58a-e4e1-5eb7-fe9d17adfbe3@redhat.com>
Date: Thu, 13 Sep 2018 17:10:14 +0200
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Subject: Re: [Qemu-devel] [PATCH v2 11/17] block-backend: Decrease in_flight
 only after callback
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To: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org
Cc: mreitz@redhat.com, famz@redhat.com, slp@redhat.com, jsnow@redhat.com, qemu-devel@nongnu.org

On 13/09/2018 14:52, Kevin Wolf wrote:
> + if (qemu_get_current_aio_context() == qemu_get_aio_context()) {
> + /* If we are in the main thread, the callback is allowed to unref
> + * the BlockBackend, so we have to hold an additional reference */
> + blk_ref(acb->rwco.blk);
> + }
> acb->common.cb(acb->common.opaque, acb->rwco.ret);
> + blk_dec_in_flight(acb->rwco.blk);
> + if (qemu_get_current_aio_context() == qemu_get_aio_context()) {
> + blk_unref(acb->rwco.blk);
> + }

Is this something that happens only for some specific callers?  That is,
which callers are sure that the callback is invoked from the main thread?

Thanks,

Paolo