On Thu, 17 Mar 2022 14:07:45 -0700 Rob Clark wrote:
> On Thu, Mar 17, 2022 at 1:45 PM Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx> wrote:
> >
> > On 3/11/2022 5:16 AM, Rob Clark wrote:
> > > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> > >
> > > The mutex wasn't really protecting anything before. Before the previous
> > > patch we could still be racing with the scheduler's kthread, as that is
> > > not necessarily frozen yet. Now that we've parked the sched threads,
> > > the only race is with jobs retiring, and that is harmless, ie.
> > >
> > > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> > > ---
> > > drivers/gpu/drm/msm/adreno/adreno_device.c | 11 +----------
> > > 1 file changed, 1 insertion(+), 10 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c
> > > index 0440a98988fc..661dfa7681fb 100644
> > > --- a/drivers/gpu/drm/msm/adreno/adreno_device.c
> > > +++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
> > > @@ -607,15 +607,6 @@ static int adreno_runtime_resume(struct device *dev)
> > > return gpu->funcs->pm_resume(gpu);
> > > }
> > >
> > > -static int active_submits(struct msm_gpu *gpu)
> > > -{
> > > - int active_submits;
> > > - mutex_lock(&gpu->active_lock);
> > > - active_submits = gpu->active_submits;
> > > - mutex_unlock(&gpu->active_lock);
> > I assumed that this lock here was to ensure proper barriers while
> > reading active_submits. Is that not required?
>
> There is a spinlock in prepare_to_wait_event() ahead of checking the
> condition, which AFAIU is a sufficient barrier
set_current_state() is instead - feel free to grep it in <linux/wait.h>
Hillf
>
> BR,
> -R
>
> >
> > -Akhil.
> > > - return active_submits;
> > > -}
> > > -
> > > static int adreno_runtime_suspend(struct device *dev)
> > > {
> > > struct msm_gpu *gpu = dev_to_gpu(dev);
> > > @@ -669,7 +660,7 @@ static int adreno_system_suspend(struct device *dev)
> > > suspend_scheduler(gpu);
> > >
> > > remaining = wait_event_timeout(gpu->retire_event,
> > > - active_submits(gpu) == 0,
> > > + gpu->active_submits == 0,
> > > msecs_to_jiffies(1000));
> > > if (remaining == 0) {
> > > dev_err(dev, "Timeout waiting for GPU to suspend\n");
> >
