Re: [PATCH 1/2] drm/msm: Move hangcheck timer restart

[Akhil P Oommen]

On 8/3/2022 10:53 PM, Rob Clark wrote:

From: Rob Clark <robdcl...@chromium.org>

Don't directly restart the hangcheck timer from the timer handler, but
instead start it after the recover_worker replays remaining jobs.

If the kthread is blocked for other reasons, there is no point to
immediately restart the timer.  Fixes a random symptom of the problem
fixed in the next patch.

Signed-off-by: Rob Clark <robdcl...@chromium.org>
---
  drivers/gpu/drm/msm/msm_gpu.c | 14 +++++++++-----
  1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
index fba85f894314..8f9c48eabf7d 100644
--- a/drivers/gpu/drm/msm/msm_gpu.c
+++ b/drivers/gpu/drm/msm/msm_gpu.c
@@ -328,6 +328,7 @@ find_submit(struct msm_ringbuffer *ring, uint32_t fence)
  }

static void retire_submits(struct msm_gpu *gpu);

+static void hangcheck_timer_reset(struct msm_gpu *gpu);

static void get_comm_cmdline(struct msm_gem_submit *submit, char **comm, char **cmd)

  {
@@ -420,6 +421,8 @@ static void recover_worker(struct kthread_work *work)
        }

if (msm_gpu_active(gpu)) {

+               bool restart_hangcheck = false;
+
                /* retire completed submits, plus the one that hung: */
                retire_submits(gpu);

@@ -436,10 +439,15 @@ static void recover_worker(struct kthread_work *work)

                        unsigned long flags;

spin_lock_irqsave(&ring->submit_lock, flags);

-                       list_for_each_entry(submit, &ring->submits, node)
+                       list_for_each_entry(submit, &ring->submits, node) {
                                gpu->funcs->submit(gpu, submit);
+                               restart_hangcheck = true;
+                       }
                        spin_unlock_irqrestore(&ring->submit_lock, flags);
                }
+
+               if (restart_hangcheck)
+                       hangcheck_timer_reset(gpu);
        }

mutex_unlock(&gpu->lock);

@@ -515,10 +523,6 @@ static void hangcheck_handler(struct timer_list *t)
                kthread_queue_work(gpu->worker, &gpu->recover_work);
        }

- /* if still more pending work, reset the hangcheck timer: */

In the scenario mentioned here, shouldn't we restart the timer?

-Akhil.

-       if (fence_after(ring->fctx->last_fence, ring->hangcheck_fence))
-               hangcheck_timer_reset(gpu);
-
        /* workaround for missing irq: */
        msm_gpu_retire(gpu);
  }