Messages in this thread | | | Date | Fri, 27 Oct 2023 16:34:26 +0200 | Subject | Re: [PATCH drm-misc-next v3] drm/sched: implement dynamic job-flow control | From | Danilo Krummrich <> |
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On 10/27/23 09:17, Boris Brezillon wrote: > Hi Danilo, > > On Thu, 26 Oct 2023 18:13:00 +0200 > Danilo Krummrich <dakr@redhat.com> wrote: > >> + >> + /** >> + * @update_job_credits: Called once the scheduler is considering this >> + * job for execution. >> + * >> + * Drivers may use this to update the job's submission credits, which is >> + * useful to e.g. deduct the number of native fences which have been >> + * signaled meanwhile. >> + * >> + * The callback must either return the new number of submission credits >> + * for the given job, or zero if no update is required. >> + * >> + * This callback is optional. >> + */ >> + u32 (*update_job_credits)(struct drm_sched_job *sched_job); > > I'm copying my late reply to v2 here so it doesn't get lost: > > I keep thinking it'd be simpler to make this a void function that > updates s_job->submission_credits directly. I also don't see the > problem with doing a sanity check on job->submission_credits. I mean, > if the driver is doing something silly, you can't do much to prevent it > anyway, except warn the user that something wrong has happened. If you > want to > > WARN_ON(job->submission_credits == 0 || > job->submission_credits > job_old_submission_credits); > > that's fine. But none of this sanity checking has to do with the > function prototype/semantics, and I'm still not comfortable with this 0 > => no-change. If there's no change, we should just leave > job->submission_credits unchanged (or return job->submission_credits) > instead of inventing a new special case.
If we can avoid letting drivers change fields of generic structures directly without any drawbacks I think we should avoid it. Currently, drivers shouldn't have the need to mess with job->credits directly. The initial value is set through drm_sched_job_init() and is updated through the return value of update_job_credits().
I'm fine getting rid of the 0 => no-change semantics though. Instead we can just WARN() on 0. However, if we do that I'd also want to change it for drm_sched_job_init() (where 0 currently defaults to 1) such that we accept 0, but WARN() accordingly.
I think it's consequent to either consistently give 0 a different meaning or just accept it but WARN() on it.
> > Regards, > > Boris >
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