linux-kernel - [PATCH 09/18] drm/scheduler: use dma-fence annotations in main thread

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Date:   Thu,  4 Jun 2020 10:12:15 +0200
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     DRI Development <dri-devel@...ts.freedesktop.org>
Cc:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-rdma@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Christian König <christian.koenig@....com>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: [PATCH 09/18] drm/scheduler: use dma-fence annotations in main thread

If the scheduler rt thread gets stuck on a mutex that we're holding
while waiting for gpu workloads to complete, we have a problem.

Add dma-fence annotations so that lockdep can check this for us.

I've tried to quite carefully review this, and I think it's at the
right spot. But obviosly no expert on drm scheduler.

Cc: linux-media@...r.kernel.org
Cc: linaro-mm-sig@...ts.linaro.org
Cc: linux-rdma@...r.kernel.org
Cc: amd-gfx@...ts.freedesktop.org
Cc: intel-gfx@...ts.freedesktop.org
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc: Christian König <christian.koenig@....com>
Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
---
 drivers/gpu/drm/scheduler/sched_main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 2f319102ae9f..06a736e506ad 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -763,9 +763,12 @@ static int drm_sched_main(void *param)
 	struct sched_param sparam = {.sched_priority = 1};
 	struct drm_gpu_scheduler *sched = (struct drm_gpu_scheduler *)param;
 	int r;
+	bool fence_cookie;
 
 	sched_setscheduler(current, SCHED_FIFO, &sparam);
 
+	fence_cookie = dma_fence_begin_signalling();
+
 	while (!kthread_should_stop()) {
 		struct drm_sched_entity *entity = NULL;
 		struct drm_sched_fence *s_fence;
@@ -823,6 +826,9 @@ static int drm_sched_main(void *param)
 
 		wake_up(&sched->job_scheduled);
 	}
+
+	dma_fence_end_signalling(fence_cookie);
+
 	return 0;
 }
 
-- 
2.26.2