On 06/06/2023 12:06, Coelho, Luciano wrote:
On Tue, 2023-06-06 at 11:06 +0100, Tvrtko Ursulin wrote:
On 05/06/2023 16:06, Jani Nikula wrote:
On Wed, 31 May 2023, Patchwork <patchwork@xxxxxxxxxxxxxxxxxxxxxx> wrote:
#### Possible regressions ####
* igt@gem_close_race@basic-process:
- fi-blb-e6850: [PASS][1] -> [ABORT][2]
[1]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_13203/fi-blb-e6850/igt@gem_close_race@xxxxxxxxxxxxxxxxxx
[2]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_117618v3/fi-blb-e6850/igt@gem_close_race@xxxxxxxxxxxxxxxxxx
- fi-hsw-4770: [PASS][3] -> [ABORT][4]
[3]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_13203/fi-hsw-4770/igt@gem_close_race@xxxxxxxxxxxxxxxxxx
[4]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_117618v3/fi-hsw-4770/igt@gem_close_race@xxxxxxxxxxxxxxxxxx
- fi-elk-e7500: [PASS][5] -> [ABORT][6]
[5]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_13203/fi-elk-e7500/igt@gem_close_race@xxxxxxxxxxxxxxxxxx
[6]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_117618v3/fi-elk-e7500/igt@gem_close_race@xxxxxxxxxxxxxxxxxx
* igt@i915_selftest@live@evict:
- bat-adlp-9: [PASS][7] -> [ABORT][8]
[7]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_13203/bat-adlp-9/igt@i915_selftest@live@xxxxxxxxxx
[8]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_117618v3/bat-adlp-9/igt@i915_selftest@live@xxxxxxxxxx
- bat-rpls-2: [PASS][9] -> [ABORT][10]
[9]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_13203/bat-rpls-2/igt@i915_selftest@live@xxxxxxxxxx
[10]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_117618v3/bat-rpls-2/igt@i915_selftest@live@xxxxxxxxxx
- bat-adlm-1: [PASS][11] -> [ABORT][12]
[11]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_13203/bat-adlm-1/igt@i915_selftest@live@xxxxxxxxxx
[12]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_117618v3/bat-adlm-1/igt@i915_selftest@live@xxxxxxxxxx
- bat-rpls-1: [PASS][13] -> [ABORT][14]
[13]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_13203/bat-rpls-1/igt@i915_selftest@live@xxxxxxxxxx
[14]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_117618v3/bat-rpls-1/igt@i915_selftest@live@xxxxxxxxxx
This still fails consistently, I have no clue why, and the above aren't
even remotely related to display.
What now? Tvrtko?
Hmm..
<4> [46.782321] Chain exists of:
(wq_completion)i915 --> (work_completion)(&i915->mm.free_work) --> &vm->mutex
<4> [46.782329] Possible unsafe locking scenario:
<4> [46.782332] CPU0 CPU1
<4> [46.782334] ---- ----
<4> [46.782337] lock(&vm->mutex);
<4> [46.782340] lock((work_completion)(&i915->mm.free_work));
<4> [46.782344] lock(&vm->mutex);
<4> [46.782348] lock((wq_completion)i915);
"(wq_completion)i915"
So it's not about the new wq even. Perhaps it is this hunk:
--- a/drivers/gpu/drm/i915/intel_wakeref.c
+++ b/drivers/gpu/drm/i915/intel_wakeref.c
@@ -75,7 +75,7 @@ void __intel_wakeref_put_last(struct intel_wakeref *wf, unsigned long flags)
/* Assume we are not in process context and so cannot sleep. */
if (flags & INTEL_WAKEREF_PUT_ASYNC || !mutex_trylock(&wf->mutex)) {
- mod_delayed_work(system_wq, &wf->work,
+ mod_delayed_work(wf->i915->wq, &wf->work,
Transformation from this patch otherwise is system_wq with the new unordered wq, so I'd try that first.
Indeed this seems to be exactly the block that is causing the issue. I
was sort of bisecting through all these changes and reverting this one
prevents the lockdep splat from happening...
So there's something that needs to be synced with the system_wq here,
but what? I need to dig into it.
AFAICT it is saying that i915->mm.free_work and engine->wakeref.work
must not be on the same ordered wq. Otherwise execbuf call trace
flushing under vm->mutex can deadlock against the free worker trying to
grab vm->mutex. If engine->wakeref.work is on a separate unordered wq it
would be safe since then execution will not be serialized with the
free_work. So just using the new i915->unordered_wq for this hunk should
work.
Regards,
Tvrtko
