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* [Intel-gfx] [PATCH] drm/i915/gt: Fix -EDEADLK handling regression
@ 2021-06-30 16:44 Ville Syrjala
  2021-06-30 19:42 ` [Intel-gfx] ✓ Fi.CI.BAT: success for " Patchwork
                   ` (2 more replies)
  0 siblings, 3 replies; 9+ messages in thread
From: Ville Syrjala @ 2021-06-30 16:44 UTC (permalink / raw)
  To: intel-gfx; +Cc: Thomas Hellström, stable

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

The conversion to ww mutexes failed to address the fence code which
already returns -EDEADLK when we run out of fences. Ww mutexes on
the other hand treat -EDEADLK as an internal errno value indicating
a need to restart the operation due to a deadlock. So now when the
fence code returns -EDEADLK the higher level code erroneously
restarts everything instead of returning the error to userspace
as is expected.

To remedy this let's switch the fence code to use a different errno
value for this. -ENOBUFS seems like a semi-reasonable unique choice.
Apart from igt the only user of this I could find is sna, and even
there all we do is dump the current fence registers from debugfs
into the X server log. So no user visible functionality is affected.
If we really cared about preserving this we could of course convert
back to -EDEADLK higher up, but doesn't seem like that's worth
the hassle here.

Not quite sure which commit specifically broke this, but I'll
just attribute it to the general gem ww mutex work.

Cc: stable@vger.kernel.org
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Thomas Hellström <thomas.hellstrom@intel.com>
Testcase: igt/gem_pread/exhaustion
Testcase: igt/gem_pwrite/basic-exhaustion
Testcase: igt/gem_fenced_exec_thrash/too-many-fences
Fixes: 80f0b679d6f0 ("drm/i915: Add an implementation for i915_gem_ww_ctx locking, v2.")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c b/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c
index cac7f3f44642..f8948de72036 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c
@@ -348,7 +348,7 @@ static struct i915_fence_reg *fence_find(struct i915_ggtt *ggtt)
 	if (intel_has_pending_fb_unpin(ggtt->vm.i915))
 		return ERR_PTR(-EAGAIN);
 
-	return ERR_PTR(-EDEADLK);
+	return ERR_PTR(-ENOBUFS);
 }
 
 int __i915_vma_pin_fence(struct i915_vma *vma)
-- 
2.31.1

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^ permalink raw reply related	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2021-07-13 20:22 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-06-30 16:44 [Intel-gfx] [PATCH] drm/i915/gt: Fix -EDEADLK handling regression Ville Syrjala
2021-06-30 19:42 ` [Intel-gfx] ✓ Fi.CI.BAT: success for " Patchwork
2021-07-01  2:48 ` [Intel-gfx] ✗ Fi.CI.IGT: failure " Patchwork
2021-07-01  7:07 ` [Intel-gfx] [PATCH] " Maarten Lankhorst
2021-07-01 17:00   ` Ville Syrjälä
2021-07-13 19:58   ` Daniel Vetter
2021-07-13 19:59     ` Daniel Vetter
2021-07-13 20:19       ` Rodrigo Vivi
2021-07-13 20:22       ` Ville Syrjälä

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