[PATCH 5/5] drm/amd/sched: signal and free remaining fences in amd_sched_entity_fini

[Marek Olšák]

Thanks for this series. I can finally finish piglit on VI.

Marek

On Thu, Sep 28, 2017 at 4:55 PM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>
> Highly concurrent Piglit runs can trigger a race condition where a pending
> SDMA job on a buffer object is never executed because the corresponding
> process is killed (perhaps due to a crash). Since the job's fences were
> never signaled, the buffer object was effectively leaked. Worse, the
> buffer was stuck wherever it happened to be at the time, possibly in VRAM.
>
> The symptom was user space processes stuck in interruptible waits with
> kernel stacks like:
>
>     [<ffffffffbc5e6722>] dma_fence_default_wait+0x112/0x250
>     [<ffffffffbc5e6399>] dma_fence_wait_timeout+0x39/0xf0
>     [<ffffffffbc5e82d2>] reservation_object_wait_timeout_rcu+0x1c2/0x300
>     [<ffffffffc03ce56f>] ttm_bo_cleanup_refs_and_unlock+0xff/0x1a0 [ttm]
>     [<ffffffffc03cf1ea>] ttm_mem_evict_first+0xba/0x1a0 [ttm]
>     [<ffffffffc03cf611>] ttm_bo_mem_space+0x341/0x4c0 [ttm]
>     [<ffffffffc03cfc54>] ttm_bo_validate+0xd4/0x150 [ttm]
>     [<ffffffffc03cffbd>] ttm_bo_init_reserved+0x2ed/0x420 [ttm]
>     [<ffffffffc042f523>] amdgpu_bo_create_restricted+0x1f3/0x470 [amdgpu]
>     [<ffffffffc042f9fa>] amdgpu_bo_create+0xda/0x220 [amdgpu]
>     [<ffffffffc04349ea>] amdgpu_gem_object_create+0xaa/0x140 [amdgpu]
>     [<ffffffffc0434f97>] amdgpu_gem_create_ioctl+0x97/0x120 [amdgpu]
>     [<ffffffffc037ddba>] drm_ioctl+0x1fa/0x480 [drm]
>     [<ffffffffc041904f>] amdgpu_drm_ioctl+0x4f/0x90 [amdgpu]
>     [<ffffffffbc23db33>] do_vfs_ioctl+0xa3/0x5f0
>     [<ffffffffbc23e0f9>] SyS_ioctl+0x79/0x90
>     [<ffffffffbc864ffb>] entry_SYSCALL_64_fastpath+0x1e/0xad
>     [<ffffffffffffffff>] 0xffffffffffffffff
>
> Signed-off-by: Nicolai Hähnle <nicolai.haehnle at amd.com>
> Acked-by: Christian König <christian.koenig at amd.com>
> ---
>  drivers/gpu/drm/amd/scheduler/gpu_scheduler.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
> index 54eb77cffd9b..32a99e980d78 100644
> --- a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
> +++ b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
> @@ -220,22 +220,27 @@ void amd_sched_entity_fini(struct amd_gpu_scheduler *sched,
>                                         amd_sched_entity_is_idle(entity));
>         amd_sched_rq_remove_entity(rq, entity);
>         if (r) {
>                 struct amd_sched_job *job;
>
>                 /* Park the kernel for a moment to make sure it isn't processing
>                  * our enity.
>                  */
>                 kthread_park(sched->thread);
>                 kthread_unpark(sched->thread);
> -               while (kfifo_out(&entity->job_queue, &job, sizeof(job)))
> +               while (kfifo_out(&entity->job_queue, &job, sizeof(job))) {
> +                       struct amd_sched_fence *s_fence = job->s_fence;
> +                       amd_sched_fence_scheduled(s_fence);
> +                       amd_sched_fence_finished(s_fence);
> +                       dma_fence_put(&s_fence->finished);
>                         sched->ops->free_job(job);
> +               }
>
>         }
>         kfifo_free(&entity->job_queue);
>  }
>
>  static void amd_sched_entity_wakeup(struct dma_fence *f, struct dma_fence_cb *cb)
>  {
>         struct amd_sched_entity *entity =
>                 container_of(cb, struct amd_sched_entity, cb);
>         entity->dependency = NULL;
> --
> 2.11.0
>
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