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

[Nicolai Hähnle]

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