On 27/07/18 15:28, Ezequiel Garcia wrote:
> On 12 June 2018 at 10:22, Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> wrote:
>> If there is a schedulable job, v4l2_m2m_try_schedule() calls
>> v4l2_m2m_try_run(). This makes the unconditional v4l2_m2m_try_run()
>> called by v4l2_m2m_job_finish superfluous. Remove it.
>>
>> Fixes: 7f98639def42 ("V4L/DVB: add memory-to-memory device helper framework for videobuf")
>> Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
>> ---
>> drivers/media/v4l2-core/v4l2-mem2mem.c | 1 -
>> 1 file changed, 1 deletion(-)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
>> index c4f963d96a79..5f9cd5b74cda 100644
>> --- a/drivers/media/v4l2-core/v4l2-mem2mem.c
>> +++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
>> @@ -339,7 +339,6 @@ void v4l2_m2m_job_finish(struct v4l2_m2m_dev *m2m_dev,
>> * allow more than one job on the job_queue per instance, each has
>> * to be scheduled separately after the previous one finishes. */
>> v4l2_m2m_try_schedule(m2m_ctx);
>> - v4l2_m2m_try_run(m2m_dev);
>> }
>> EXPORT_SYMBOL(v4l2_m2m_job_finish);
>>
>
> Hi Mauro, Hans,
>
> Please note that this patch (which is merged in Mauro's) introduces an issue
> in the following scenario:
>
> 1) Context A schedules, queues and runs job A.
> 2) While the m2m device is running, context B schedules
> and queues job B. Job B cannot run, because it has to
> wait for job A.
> 3) Job A completes, calls v4l2_m2m_job_finish, and tries
> to queue a job for context A, but since the context is
> empty it won't do anything.
>
> In this scenario, queued job B will never run.
>
> The issue is fixed in https://patchwork.kernel.org/patch/10544487/
>
> I don't know what's the best way to proceed here, pick the fix or simply
> drop this commit instead?
>
It's best to fix it, but I did a quick review of that patch and I had a
few comments.
I'm not sure what is going on here, so if you can take another look?
If there is indeed a regression, them post the fix as a separate patch.
Fixes can of course always be applied, irrespective of the merge window.
Regards,
Hans
