Revert "drm/msm/gpu: Push gpu lock down past runpm"

From: Rob Clark <robdclark@chromium.org>

This reverts commit abe2023b4cea192ab266b351fd38dc9dbd846df0.

Changing the locking order means that scheduler/msm_job_run() can race
with the recovery kthread worker, with the result that the GPU gets an
extra runpm get when we are trying to power it off.  Leaving the GPU in
an unrecovered state.

I'll need to come up with a different scheme for appeasing lockdep.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/gpu/drm/msm/msm_gpu.c        | 11 +++++------
 drivers/gpu/drm/msm/msm_ringbuffer.c |  7 +++++--
 2 files changed, 10 insertions(+), 8 deletions(-)

On Tue, Jan 09, 2024 at 10:22:17AM -0800, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> This reverts commit abe2023b4cea192ab266b351fd38dc9dbd846df0.
> 
> Changing the locking order means that scheduler/msm_job_run() can race
> with the recovery kthread worker, with the result that the GPU gets an
> extra runpm get when we are trying to power it off.  Leaving the GPU in
> an unrecovered state.

The recovery kthread is supposed to stop all the relevant schedulers,
which should remove any possible race conditions. So unless there's more
going on, or you have your own recovery kthread (don't, reuse the one from
the scheduler with your own work items, that's why you can provide that)
this looks like an incomplete/incorrect explanation ... ?

Slightly confused
-Sima

> 
> I'll need to come up with a different scheme for appeasing lockdep.
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
>  drivers/gpu/drm/msm/msm_gpu.c        | 11 +++++------
>  drivers/gpu/drm/msm/msm_ringbuffer.c |  7 +++++--
>  2 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> index 095390774f22..655002b21b0d 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.c
> +++ b/drivers/gpu/drm/msm/msm_gpu.c
> @@ -751,12 +751,14 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>  	struct msm_ringbuffer *ring = submit->ring;
>  	unsigned long flags;
>  
> -	pm_runtime_get_sync(&gpu->pdev->dev);
> +	WARN_ON(!mutex_is_locked(&gpu->lock));
>  
> -	mutex_lock(&gpu->lock);
> +	pm_runtime_get_sync(&gpu->pdev->dev);
>  
>  	msm_gpu_hw_init(gpu);
>  
> +	submit->seqno = submit->hw_fence->seqno;
> +
>  	update_sw_cntrs(gpu);
>  
>  	/*
> @@ -781,11 +783,8 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>  	gpu->funcs->submit(gpu, submit);
>  	gpu->cur_ctx_seqno = submit->queue->ctx->seqno;
>  
> -	hangcheck_timer_reset(gpu);
> -
> -	mutex_unlock(&gpu->lock);
> -
>  	pm_runtime_put(&gpu->pdev->dev);
> +	hangcheck_timer_reset(gpu);
>  }
>  
>  /*
> diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c
> index e0ed27739449..548f5266a7d3 100644
> --- a/drivers/gpu/drm/msm/msm_ringbuffer.c
> +++ b/drivers/gpu/drm/msm/msm_ringbuffer.c
> @@ -21,8 +21,6 @@ static struct dma_fence *msm_job_run(struct drm_sched_job *job)
>  
>  	msm_fence_init(submit->hw_fence, fctx);
>  
> -	submit->seqno = submit->hw_fence->seqno;
> -
>  	mutex_lock(&priv->lru.lock);
>  
>  	for (i = 0; i < submit->nr_bos; i++) {
> @@ -35,8 +33,13 @@ static struct dma_fence *msm_job_run(struct drm_sched_job *job)
>  
>  	mutex_unlock(&priv->lru.lock);
>  
> +	/* TODO move submit path over to using a per-ring lock.. */
> +	mutex_lock(&gpu->lock);
> +
>  	msm_gpu_submit(gpu, submit);
>  
> +	mutex_unlock(&gpu->lock);
> +
>  	return dma_fence_get(submit->hw_fence);
>  }
>  
> -- 
> 2.43.0
>

On Wed, Jan 10, 2024 at 2:50 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> On Tue, Jan 09, 2024 at 10:22:17AM -0800, Rob Clark wrote:
> > From: Rob Clark <robdclark@chromium.org>
> >
> > This reverts commit abe2023b4cea192ab266b351fd38dc9dbd846df0.
> >
> > Changing the locking order means that scheduler/msm_job_run() can race
> > with the recovery kthread worker, with the result that the GPU gets an
> > extra runpm get when we are trying to power it off.  Leaving the GPU in
> > an unrecovered state.
>
> The recovery kthread is supposed to stop all the relevant schedulers,
> which should remove any possible race conditions. So unless there's more
> going on, or you have your own recovery kthread (don't, reuse the one from
> the scheduler with your own work items, that's why you can provide that)
> this looks like an incomplete/incorrect explanation ... ?
>
> Slightly confused

msm still uses it's own recovery, which pre-dates the scheduler
conversion.  At one point (a yr or two back?) I started looking at
integrating recovery w/ scheduler.. at the time I think you talked me
out of it, but I don't remember the reason

BR,
-R

> -Sima
>
> >
> > I'll need to come up with a different scheme for appeasing lockdep.
> >
> > Signed-off-by: Rob Clark <robdclark@chromium.org>
> > ---
> >  drivers/gpu/drm/msm/msm_gpu.c        | 11 +++++------
> >  drivers/gpu/drm/msm/msm_ringbuffer.c |  7 +++++--
> >  2 files changed, 10 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> > index 095390774f22..655002b21b0d 100644
> > --- a/drivers/gpu/drm/msm/msm_gpu.c
> > +++ b/drivers/gpu/drm/msm/msm_gpu.c
> > @@ -751,12 +751,14 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
> >       struct msm_ringbuffer *ring = submit->ring;
> >       unsigned long flags;
> >
> > -     pm_runtime_get_sync(&gpu->pdev->dev);
> > +     WARN_ON(!mutex_is_locked(&gpu->lock));
> >
> > -     mutex_lock(&gpu->lock);
> > +     pm_runtime_get_sync(&gpu->pdev->dev);
> >
> >       msm_gpu_hw_init(gpu);
> >
> > +     submit->seqno = submit->hw_fence->seqno;
> > +
> >       update_sw_cntrs(gpu);
> >
> >       /*
> > @@ -781,11 +783,8 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
> >       gpu->funcs->submit(gpu, submit);
> >       gpu->cur_ctx_seqno = submit->queue->ctx->seqno;
> >
> > -     hangcheck_timer_reset(gpu);
> > -
> > -     mutex_unlock(&gpu->lock);
> > -
> >       pm_runtime_put(&gpu->pdev->dev);
> > +     hangcheck_timer_reset(gpu);
> >  }
> >
> >  /*
> > diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c
> > index e0ed27739449..548f5266a7d3 100644
> > --- a/drivers/gpu/drm/msm/msm_ringbuffer.c
> > +++ b/drivers/gpu/drm/msm/msm_ringbuffer.c
> > @@ -21,8 +21,6 @@ static struct dma_fence *msm_job_run(struct drm_sched_job *job)
> >
> >       msm_fence_init(submit->hw_fence, fctx);
> >
> > -     submit->seqno = submit->hw_fence->seqno;
> > -
> >       mutex_lock(&priv->lru.lock);
> >
> >       for (i = 0; i < submit->nr_bos; i++) {
> > @@ -35,8 +33,13 @@ static struct dma_fence *msm_job_run(struct drm_sched_job *job)
> >
> >       mutex_unlock(&priv->lru.lock);
> >
> > +     /* TODO move submit path over to using a per-ring lock.. */
> > +     mutex_lock(&gpu->lock);
> > +
> >       msm_gpu_submit(gpu, submit);
> >
> > +     mutex_unlock(&gpu->lock);
> > +
> >       return dma_fence_get(submit->hw_fence);
> >  }
> >
> > --
> > 2.43.0
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch