On 18/01/2017 16:43, Stefan Hajnoczi wrote:
> On Fri, Jan 13, 2017 at 02:17:25PM +0100, Paolo Bonzini wrote:
>> diff --git a/block/null.c b/block/null.c
>> index b300390..356209a 100644
>> --- a/block/null.c
>> +++ b/block/null.c
>> @@ -141,7 +141,11 @@ static void null_bh_cb(void *opaque)
>> static void null_timer_cb(void *opaque)
>> {
>> NullAIOCB *acb = opaque;
>> + AioContext *ctx = bdrv_get_aio_context(acb->common.bs);
>> +
>> + aio_context_acquire(ctx);
>> acb->common.cb(acb->common.opaque, 0);
>> + aio_context_release(ctx);
>> timer_deinit(&acb->timer);
>> qemu_aio_unref(acb);
>
> Is qemu_aio_unref() thread-safe?qemu_aio_ref()/qemu_aio_unref() is only used by bdrv_aio_cancel, which in turn is not used by dataplane. So in the multithreaded case qemu_aio_unref() is effectively qemu_aio_free(). Probably needs more documentation, or a different implementation of bdrv_aio_cancel (e.g. replacing the reference counting with a NotifierList of some kind). Let me know what you prefer for v2. Paolo
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