drm/amdgpu/userq: unlock cancel_delayed_work_sync for hang_detect_work

cancel_delayed_work_sync for work hand_detect_work should not be
locked since the amdgpu_userq_hang_detect_work also need the same
mutex and when they run together it could be a deadlock.

we do not need to hold the mutex for
cancel_delayed_work_sync(&queue->hang_detect_work). With this in place
if cancel and worker thread run at same time they will not deadlock.

Due to any failures if there is a hand detect and reset that there a
deadlock scenarios between cancel and running the main thread.

[ 243.118276] task:kworker/9:0 state:D stack:0 pid:73 tgid:73 ppid:2 task_flags:0x4208060 flags:0x00080000
[ 243.118283] Workqueue: events amdgpu_userq_hang_detect_work [amdgpu]
[ 243.118636] Call Trace:
[ 243.118639] <TASK>
[ 243.118644] __schedule+0x581/0x1810
[ 243.118649] ? srso_return_thunk+0x5/0x5f
[ 243.118656] ? srso_return_thunk+0x5/0x5f
[ 243.118659] ? wake_up_process+0x15/0x20
[ 243.118665] schedule+0x64/0xe0
[ 243.118668] schedule_preempt_disabled+0x15/0x30
[ 243.118671] __mutex_lock+0x346/0x950
[ 243.118677] __mutex_lock_slowpath+0x13/0x20
[ 243.118681] mutex_lock+0x2c/0x40
[ 243.118684] amdgpu_userq_hang_detect_work+0x63/0x90 [amdgpu]
[ 243.118888] process_scheduled_works+0x1f0/0x450
[ 243.118894] worker_thread+0x27f/0x370
[ 243.118899] kthread+0x1ed/0x210
[ 243.118903] ? __pfx_worker_thread+0x10/0x10
[ 243.118906] ? srso_return_thunk+0x5/0x5f
[ 243.118909] ? __pfx_kthread+0x10/0x10
[ 243.118913] ret_from_fork+0x10f/0x1b0
[ 243.118916] ? __pfx_kthread+0x10/0x10
[ 243.118920] ret_from_fork_asm+0x1a/0x30

Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
index 5619233e1b68e01468bcf0e5e3375a0a5fc8b177..3cc6e8da48a26151a8f878b0a9e98ec2500fe444 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
@@ -623,13 +623,14 @@ amdgpu_userq_destroy(struct amdgpu_userq_mgr *uq_mgr, struct amdgpu_usermode_que
        int r = 0;
 
        cancel_delayed_work_sync(&uq_mgr->resume_work);
+
+       /* Cancel any pending hang detection work and cleanup */
+       cancel_delayed_work_sync(&queue->hang_detect_work);
+
        mutex_lock(&uq_mgr->userq_mutex);
+       queue->hang_detect_fence = NULL;
        amdgpu_userq_wait_for_last_fence(queue);
-       /* Cancel any pending hang detection work and cleanup */
-       if (queue->hang_detect_fence) {
-               cancel_delayed_work_sync(&queue->hang_detect_work);
-               queue->hang_detect_fence = NULL;
-       }
+
        r = amdgpu_bo_reserve(queue->db_obj.obj, true);
        if (!r) {
                amdgpu_bo_unpin(queue->db_obj.obj);