6.6-stable review patch. If anyone has any objections, please let me know.
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From: Janusz Krzysztofik janusz.krzysztofik@linux.intel.com
[ Upstream commit a5aa7bc1fca78c7fa127d9e33aa94a0c9066c1d6 ]
The following error has been reported sporadically by CI when a test unbinds the i915 driver on a ring submission platform:
<4> [239.330153] ------------[ cut here ]------------ <4> [239.330166] i915 0000:00:02.0: [drm] drm_WARN_ON(dev_priv->mm.shrink_count) <4> [239.330196] WARNING: CPU: 1 PID: 18570 at drivers/gpu/drm/i915/i915_gem.c:1309 i915_gem_cleanup_early+0x13e/0x150 [i915] ... <4> [239.330640] RIP: 0010:i915_gem_cleanup_early+0x13e/0x150 [i915] ... <4> [239.330942] Call Trace: <4> [239.330944] <TASK> <4> [239.330949] i915_driver_late_release+0x2b/0xa0 [i915] <4> [239.331202] i915_driver_release+0x86/0xa0 [i915] <4> [239.331482] devm_drm_dev_init_release+0x61/0x90 <4> [239.331494] devm_action_release+0x15/0x30 <4> [239.331504] release_nodes+0x3d/0x120 <4> [239.331517] devres_release_all+0x96/0xd0 <4> [239.331533] device_unbind_cleanup+0x12/0x80 <4> [239.331543] device_release_driver_internal+0x23a/0x280 <4> [239.331550] ? bus_find_device+0xa5/0xe0 <4> [239.331563] device_driver_detach+0x14/0x20 ... <4> [357.719679] ---[ end trace 0000000000000000 ]---
If the test also unloads the i915 module then that's followed with:
<3> [357.787478] ============================================================================= <3> [357.788006] BUG i915_vma (Tainted: G U W N ): Objects remaining on __kmem_cache_shutdown() <3> [357.788031] ----------------------------------------------------------------------------- <3> [357.788204] Object 0xffff888109e7f480 @offset=29824 <3> [357.788670] Allocated in i915_vma_instance+0xee/0xc10 [i915] age=292729 cpu=4 pid=2244 <4> [357.788994] i915_vma_instance+0xee/0xc10 [i915] <4> [357.789290] init_status_page+0x7b/0x420 [i915] <4> [357.789532] intel_engines_init+0x1d8/0x980 [i915] <4> [357.789772] intel_gt_init+0x175/0x450 [i915] <4> [357.790014] i915_gem_init+0x113/0x340 [i915] <4> [357.790281] i915_driver_probe+0x847/0xed0 [i915] <4> [357.790504] i915_pci_probe+0xe6/0x220 [i915] ...
Closer analysis of CI results history has revealed a dependency of the error on a few IGT tests, namely: - igt@api_intel_allocator@fork-simple-stress-signal, - igt@api_intel_allocator@two-level-inception-interruptible, - igt@gem_linear_blits@interruptible, - igt@prime_mmap_coherency@ioctl-errors, which invisibly trigger the issue, then exhibited with first driver unbind attempt.
All of the above tests perform actions which are actively interrupted with signals. Further debugging has allowed to narrow that scope down to DRM_IOCTL_I915_GEM_EXECBUFFER2, and ring_context_alloc(), specific to ring submission, in particular.
If successful then that function, or its execlists or GuC submission equivalent, is supposed to be called only once per GEM context engine, followed by raise of a flag that prevents the function from being called again. The function is expected to unwind its internal errors itself, so it may be safely called once more after it returns an error.
In case of ring submission, the function first gets a reference to the engine's legacy timeline and then allocates a VMA. If the VMA allocation fails, e.g. when i915_vma_instance() called from inside is interrupted with a signal, then ring_context_alloc() fails, leaving the timeline held referenced. On next I915_GEM_EXECBUFFER2 IOCTL, another reference to the timeline is got, and only that last one is put on successful completion. As a consequence, the legacy timeline, with its underlying engine status page's VMA object, is still held and not released on driver unbind.
Get the legacy timeline only after successful allocation of the context engine's VMA.
v2: Add a note on other submission methods (Krzysztof Karas): Both execlists and GuC submission use lrc_alloc() which seems free from a similar issue.
Fixes: 75d0a7f31eec ("drm/i915: Lift timeline into intel_context") Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12061 Cc: Chris Wilson chris.p.wilson@linux.intel.com Cc: Matthew Auld matthew.auld@intel.com Cc: Krzysztof Karas krzysztof.karas@intel.com Reviewed-by: Sebastian Brzezinka sebastian.brzezinka@intel.com Reviewed-by: Krzysztof Niemiec krzysztof.niemiec@intel.com Signed-off-by: Janusz Krzysztofik janusz.krzysztofik@linux.intel.com Reviewed-by: Nitin Gote nitin.r.gote@intel.com Reviewed-by: Andi Shyti andi.shyti@linux.intel.com Signed-off-by: Andi Shyti andi.shyti@linux.intel.com Link: https://lore.kernel.org/r/20250611104352.1014011-2-janusz.krzysztofik@linux.... (cherry picked from commit cc43422b3cc79eacff4c5a8ba0d224688ca9dd4f) Signed-off-by: Joonas Lahtinen joonas.lahtinen@linux.intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/i915/gt/intel_ring_submission.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c index 92085ffd23de0..4eb78895773f6 100644 --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c @@ -573,7 +573,6 @@ static int ring_context_alloc(struct intel_context *ce) /* One ringbuffer to rule them all */ GEM_BUG_ON(!engine->legacy.ring); ce->ring = engine->legacy.ring; - ce->timeline = intel_timeline_get(engine->legacy.timeline);
GEM_BUG_ON(ce->state); if (engine->context_size) { @@ -586,6 +585,8 @@ static int ring_context_alloc(struct intel_context *ce) ce->state = vma; }
+ ce->timeline = intel_timeline_get(engine->legacy.timeline); + return 0; }