Re: [PATCH v10 18/21] job.c: enable job lock/unlock and remove Aiocontext locks

[Emanuele Giuseppe Esposito]

Am 17/08/2022 um 20:54 schrieb Vladimir Sementsov-Ogievskiy:
> On 8/16/22 15:52, Emanuele Giuseppe Esposito wrote:
>>>>    }
>>>> @@ -501,8 +481,12 @@ void job_unref_locked(Job *job)>
>>>> assert(!job->txn);
>>>>              if (job->driver->free) {
>>>> +            AioContext *aio_context = job->aio_context;
>>>>                job_unlock();
>>>> +            /* FIXME: aiocontext lock is required because cb calls
>>>> blk_unref */
>>>> +            aio_context_acquire(aio_context);
>>>>                job->driver->free(job);
>>>> +            aio_context_release(aio_context);
>>> So, job_unref_locked() must be called with aio_context not locked,
>>> otherwise we dead-lock here? That should be documented in function
>>> declaration comment.
>>>
>>> For example in qemu-img.c in run_block_job() we do exactly that: call
>>> job_unref_locked()  inside aio-context lock critical seaction..
>> No, job_unref_locked has also status and refcnt and all the other fields
>> that need to be protectd. Only free must be called without job lock held.
>>
> 
> I mean, don't we try here to acquire aio_context twice, when we call
> job_unref_locked() with aio_context _already_ acquired?
> 
You're right, so why do we need the AioContext lock in qemu-img then?
All jobs API don't need it, aio_poll seems not to need it either, and
progress API has its own lock.

I guess I could remove it?

Emanuele