Re: [PATCH 2/2] drm/msm: Embed the hw_fence in msm_gem_submit
From: Rob Clark
Date: Mon Mar 13 2023 - 10:45:47 EST
On Mon, Mar 13, 2023 at 12:19 AM Christian König
<christian.koenig@xxxxxxx> wrote:
>
> Am 11.03.23 um 18:35 schrieb Rob Clark:
> > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> >
> > Avoid allocating memory in job_run() by embedding the fence in the
> > submit object. Since msm gpu fences are always 1:1 with msm_gem_submit
> > we can just use the fence's refcnt to track the submit. And since we
> > can get the fence ctx from the submit we can just drop the msm_fence
> > struct altogether. This uses the new dma_fence_init_noref() to deal
> > with the fact that the fence's refcnt is initialized when the submit is
> > created, long before job_run().
>
> Well this is a very very bad idea, we made the same mistake with amdgpu
> as well.
>
> It's true that you should not have any memory allocation in your run_job
> callback, but you could also just allocate the hw fence during job
> creation and initializing it later on.
>
> I've suggested to embed the fence into the job for amdgpu because some
> people insisted of re-submitting jobs during timeout and GPU reset. This
> turned into a nightmare with tons of bug fixes on top of bug fixes on
> top of bug fixes because it messes up the job and fence lifetime as
> defined by the DRM scheduler and DMA-buf framework.
>
> Luben is currently working on cleaning all this up.
This actually shouldn't be a problem with msm, as the fence doesn't
change if there is a gpu reset. We simply signal the fence for the
offending job, reset the GPU, and re-play the remaining in-flight jobs
(ie. things that already had their job_run() called) with the original
fences. (We don't use gpu sched's reset/timeout handling.. when I
migrated to gpu sched I kept our existing hangcheck/recovery
mechanism.)
BR,
-R
> Regards,
> Christian.
>
> >
> > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> > ---
> > Note that this applies on top of https://patchwork.freedesktop.org/series/93035/
> > out of convenience for myself, but I can re-work it to go before
> > depending on the order that things land.
> >
> > drivers/gpu/drm/msm/msm_fence.c | 45 +++++++++++-----------------
> > drivers/gpu/drm/msm/msm_fence.h | 2 +-
> > drivers/gpu/drm/msm/msm_gem.h | 10 +++----
> > drivers/gpu/drm/msm/msm_gem_submit.c | 8 ++---
> > drivers/gpu/drm/msm/msm_gpu.c | 4 +--
> > drivers/gpu/drm/msm/msm_ringbuffer.c | 4 +--
> > 6 files changed, 31 insertions(+), 42 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_fence.c b/drivers/gpu/drm/msm/msm_fence.c
> > index 51b461f32103..51f9f1f0cb66 100644
> > --- a/drivers/gpu/drm/msm/msm_fence.c
> > +++ b/drivers/gpu/drm/msm/msm_fence.c
> > @@ -103,14 +103,9 @@ void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence)
> > spin_unlock_irqrestore(&fctx->spinlock, flags);
> > }
> >
> > -struct msm_fence {
> > - struct dma_fence base;
> > - struct msm_fence_context *fctx;
> > -};
> > -
> > -static inline struct msm_fence *to_msm_fence(struct dma_fence *fence)
> > +static inline struct msm_gem_submit *fence_to_submit(struct dma_fence *fence)
> > {
> > - return container_of(fence, struct msm_fence, base);
> > + return container_of(fence, struct msm_gem_submit, hw_fence);
> > }
> >
> > static const char *msm_fence_get_driver_name(struct dma_fence *fence)
> > @@ -120,20 +115,20 @@ static const char *msm_fence_get_driver_name(struct dma_fence *fence)
> >
> > static const char *msm_fence_get_timeline_name(struct dma_fence *fence)
> > {
> > - struct msm_fence *f = to_msm_fence(fence);
> > - return f->fctx->name;
> > + struct msm_gem_submit *submit = fence_to_submit(fence);
> > + return submit->ring->fctx->name;
> > }
> >
> > static bool msm_fence_signaled(struct dma_fence *fence)
> > {
> > - struct msm_fence *f = to_msm_fence(fence);
> > - return msm_fence_completed(f->fctx, f->base.seqno);
> > + struct msm_gem_submit *submit = fence_to_submit(fence);
> > + return msm_fence_completed(submit->ring->fctx, fence->seqno);
> > }
> >
> > static void msm_fence_set_deadline(struct dma_fence *fence, ktime_t deadline)
> > {
> > - struct msm_fence *f = to_msm_fence(fence);
> > - struct msm_fence_context *fctx = f->fctx;
> > + struct msm_gem_submit *submit = fence_to_submit(fence);
> > + struct msm_fence_context *fctx = submit->ring->fctx;
> > unsigned long flags;
> > ktime_t now;
> >
> > @@ -165,26 +160,22 @@ static void msm_fence_set_deadline(struct dma_fence *fence, ktime_t deadline)
> > spin_unlock_irqrestore(&fctx->spinlock, flags);
> > }
> >
> > +static void msm_fence_release(struct dma_fence *fence)
> > +{
> > + __msm_gem_submit_destroy(fence_to_submit(fence));
> > +}
> > +
> > static const struct dma_fence_ops msm_fence_ops = {
> > .get_driver_name = msm_fence_get_driver_name,
> > .get_timeline_name = msm_fence_get_timeline_name,
> > .signaled = msm_fence_signaled,
> > .set_deadline = msm_fence_set_deadline,
> > + .release = msm_fence_release,
> > };
> >
> > -struct dma_fence *
> > -msm_fence_alloc(struct msm_fence_context *fctx)
> > +void
> > +msm_fence_init(struct msm_fence_context *fctx, struct dma_fence *f)
> > {
> > - struct msm_fence *f;
> > -
> > - f = kzalloc(sizeof(*f), GFP_KERNEL);
> > - if (!f)
> > - return ERR_PTR(-ENOMEM);
> > -
> > - f->fctx = fctx;
> > -
> > - dma_fence_init(&f->base, &msm_fence_ops, &fctx->spinlock,
> > - fctx->context, ++fctx->last_fence);
> > -
> > - return &f->base;
> > + dma_fence_init_noref(f, &msm_fence_ops, &fctx->spinlock,
> > + fctx->context, ++fctx->last_fence);
> > }
> > diff --git a/drivers/gpu/drm/msm/msm_fence.h b/drivers/gpu/drm/msm/msm_fence.h
> > index cdaebfb94f5c..8fca37e9773b 100644
> > --- a/drivers/gpu/drm/msm/msm_fence.h
> > +++ b/drivers/gpu/drm/msm/msm_fence.h
> > @@ -81,7 +81,7 @@ void msm_fence_context_free(struct msm_fence_context *fctx);
> > bool msm_fence_completed(struct msm_fence_context *fctx, uint32_t fence);
> > void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence);
> >
> > -struct dma_fence * msm_fence_alloc(struct msm_fence_context *fctx);
> > +void msm_fence_init(struct msm_fence_context *fctx, struct dma_fence *f);
> >
> > static inline bool
> > fence_before(uint32_t a, uint32_t b)
> > diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
> > index c4844cf3a585..e06afed99d5b 100644
> > --- a/drivers/gpu/drm/msm/msm_gem.h
> > +++ b/drivers/gpu/drm/msm/msm_gem.h
> > @@ -259,10 +259,10 @@ struct msm_gem_submit {
> > struct ww_acquire_ctx ticket;
> > uint32_t seqno; /* Sequence number of the submit on the ring */
> >
> > - /* Hw fence, which is created when the scheduler executes the job, and
> > + /* Hw fence, which is initialized when the scheduler executes the job, and
> > * is signaled when the hw finishes (via seqno write from cmdstream)
> > */
> > - struct dma_fence *hw_fence;
> > + struct dma_fence hw_fence;
> >
> > /* Userspace visible fence, which is signaled by the scheduler after
> > * the hw_fence is signaled.
> > @@ -309,16 +309,16 @@ static inline struct msm_gem_submit *to_msm_submit(struct drm_sched_job *job)
> > return container_of(job, struct msm_gem_submit, base);
> > }
> >
> > -void __msm_gem_submit_destroy(struct kref *kref);
> > +void __msm_gem_submit_destroy(struct msm_gem_submit *submit);
> >
> > static inline void msm_gem_submit_get(struct msm_gem_submit *submit)
> > {
> > - kref_get(&submit->ref);
> > + dma_fence_get(&submit->hw_fence);
> > }
> >
> > static inline void msm_gem_submit_put(struct msm_gem_submit *submit)
> > {
> > - kref_put(&submit->ref, __msm_gem_submit_destroy);
> > + dma_fence_put(&submit->hw_fence);
> > }
> >
> > void msm_submit_retire(struct msm_gem_submit *submit);
> > diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> > index be4bf77103cd..522c8c82e827 100644
> > --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> > +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> > @@ -47,7 +47,7 @@ static struct msm_gem_submit *submit_create(struct drm_device *dev,
> > return ERR_PTR(ret);
> > }
> >
> > - kref_init(&submit->ref);
> > + kref_init(&submit->hw_fence.refcount);
> > submit->dev = dev;
> > submit->aspace = queue->ctx->aspace;
> > submit->gpu = gpu;
> > @@ -65,10 +65,9 @@ static struct msm_gem_submit *submit_create(struct drm_device *dev,
> > return submit;
> > }
> >
> > -void __msm_gem_submit_destroy(struct kref *kref)
> > +/* Called when the hw_fence is destroyed: */
> > +void __msm_gem_submit_destroy(struct msm_gem_submit *submit)
> > {
> > - struct msm_gem_submit *submit =
> > - container_of(kref, struct msm_gem_submit, ref);
> > unsigned i;
> >
> > if (submit->fence_id) {
> > @@ -78,7 +77,6 @@ void __msm_gem_submit_destroy(struct kref *kref)
> > }
> >
> > dma_fence_put(submit->user_fence);
> > - dma_fence_put(submit->hw_fence);
> >
> > put_pid(submit->pid);
> > msm_submitqueue_put(submit->queue);
> > diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> > index 380249500325..a82d11dd5fcf 100644
> > --- a/drivers/gpu/drm/msm/msm_gpu.c
> > +++ b/drivers/gpu/drm/msm/msm_gpu.c
> > @@ -716,7 +716,7 @@ static void retire_submits(struct msm_gpu *gpu)
> > * been signalled, then later submits are not signalled
> > * either, so we are also done.
> > */
> > - if (submit && dma_fence_is_signaled(submit->hw_fence)) {
> > + if (submit && dma_fence_is_signaled(&submit->hw_fence)) {
> > retire_submit(gpu, ring, submit);
> > } else {
> > break;
> > @@ -760,7 +760,7 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
> >
> > msm_gpu_hw_init(gpu);
> >
> > - submit->seqno = submit->hw_fence->seqno;
> > + submit->seqno = submit->hw_fence.seqno;
> >
> > msm_rd_dump_submit(priv->rd, submit, NULL);
> >
> > diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c
> > index 57a8e9564540..5c54befa2427 100644
> > --- a/drivers/gpu/drm/msm/msm_ringbuffer.c
> > +++ b/drivers/gpu/drm/msm/msm_ringbuffer.c
> > @@ -18,7 +18,7 @@ static struct dma_fence *msm_job_run(struct drm_sched_job *job)
> > struct msm_gpu *gpu = submit->gpu;
> > int i;
> >
> > - submit->hw_fence = msm_fence_alloc(fctx);
> > + msm_fence_init(fctx, &submit->hw_fence);
> >
> > for (i = 0; i < submit->nr_bos; i++) {
> > struct drm_gem_object *obj = &submit->bos[i].obj->base;
> > @@ -37,7 +37,7 @@ static struct dma_fence *msm_job_run(struct drm_sched_job *job)
> >
> > mutex_unlock(&gpu->lock);
> >
> > - return dma_fence_get(submit->hw_fence);
> > + return dma_fence_get(&submit->hw_fence);
> > }
> >
> > static void msm_job_free(struct drm_sched_job *job)
>