Am 01.02.23 um 17:48 schrieb Guilherme G. Piccoli:
Currently amdgpu calls drm_sched_fini() from the fence driver sw fini
routine - such function is expected to be called only after the
respective init function - drm_sched_init() - was executed successfully.
Happens that we faced a driver probe failure in the Steam Deck
recently, and the function drm_sched_fini() was called even without
its counter-part had been previously called, causing the following oops:
amdgpu: probe of 0000:04:00.0 failed with error -110
BUG: kernel NULL pointer dereference, address: 0000000000000090
PGD 0 P4D 0
Oops: 0002 [#1] PREEMPT SMP NOPTI
CPU: 0 PID: 609 Comm: systemd-udevd Not tainted 6.2.0-rc3-gpiccoli #338
Hardware name: Valve Jupiter/Jupiter, BIOS F7A0113 11/04/2022
RIP: 0010:drm_sched_fini+0x84/0xa0 [gpu_sched]
[...]
Call Trace:
<TASK>
amdgpu_fence_driver_sw_fini+0xc8/0xd0 [amdgpu]
amdgpu_device_fini_sw+0x2b/0x3b0 [amdgpu]
amdgpu_driver_release_kms+0x16/0x30 [amdgpu]
devm_drm_dev_init_release+0x49/0x70
[...]
To prevent that, check if the drm_sched was properly initialized for a
given ring before calling its fini counter-part.
Notice ideally we'd use sched.ready for that; such field is set as the latest
thing on drm_sched_init(). But amdgpu seems to "override" the meaning of such
field - in the above oops for example, it was a GFX ring causing the crash, and
the sched.ready field was set to true in the ring init routine, regardless of
the state of the DRM scheduler. Hence, we ended-up using sched.ops as per
Christian's suggestion [0].
[0] https://lore.kernel.org/amd-gfx/984ee981-2906-0eaf-ccec-9f80975cb136@xxxxxxx/
Fixes: 067f44c8b459 ("drm/amdgpu: avoid over-handle of fence driver fini in s3 test (v2)")
Suggested-by: Christian König <christian.koenig@xxxxxxx>
Cc: Guchun Chen <guchun.chen@xxxxxxx>
Cc: Luben Tuikov <luben.tuikov@xxxxxxx>
Cc: Mario Limonciello <mario.limonciello@xxxxxxx>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
index 00444203220d..3b962cb680a6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
@@ -618,7 +618,13 @@ void amdgpu_fence_driver_sw_fini(struct amdgpu_device *adev)
if (!ring || !ring->fence_drv.initialized)
continue;
- if (!ring->no_scheduler)
+ /*
+ * Notice we check for sched.ops since there's some
+ * override on the meaning of sched.ready by amdgpu.
+ * The natural check would be sched.ready, which is
+ * set as drm_sched_init() finishes...
+ */
+ if (!ring->no_scheduler && ring->sched.ops)
drm_sched_fini(&ring->sched);
I think we should drop the check for no_scheduler here and just call
drm_sched_fini() when the scheduler instance was initialized before.
Background is that I've found a couple of places where we potentially
set no_scheduler to false after the scheduler was already initialized.
This is then probably leading to a memory leak or worth.
Regards,
Christian.
for (j = 0; j <= ring->fence_drv.num_fences_mask; ++j)
