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* [PATCH v3] drm/xe: Remove unwanted mutex locking
@ 2024-05-29 21:39 Niranjana Vishwanathapura
  2024-05-29 21:45 ` ✓ CI.Patch_applied: success for drm/xe: Remove unwanted mutex locking (rev3) Patchwork
                   ` (8 more replies)
  0 siblings, 9 replies; 10+ messages in thread
From: Niranjana Vishwanathapura @ 2024-05-29 21:39 UTC (permalink / raw)
  To: intel-xe; +Cc: rodrigo.vivi

Do not hold xef->exec_queue.lock mutex while parsing the xarray
xef->exec_queue.xa in xe_file_close() as it is not needed and
will cause an unwanted dependency between this lock and the vm->lock.

This lock protects the exec queue lookup and reference taking which
doesn't apply to this code path. When FD is closing, IOCTLs presumably
can't be modifying the xarray.

v2: Update commit text (Matt Brost)
v3: Add more code comment (Rodrigo Vivi)

Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Jagmeet Randhawa <jagmeet.randhawa@intel.com>
---
 drivers/gpu/drm/xe/xe_device.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index f04b11e45c2d..bf4c4306f6d3 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -96,12 +96,15 @@ static void xe_file_close(struct drm_device *dev, struct drm_file *file)
 	struct xe_exec_queue *q;
 	unsigned long idx;
 
-	mutex_lock(&xef->exec_queue.lock);
+	/*
+	 * No need for exec_queue.lock here as there is no contention at
+	 * this point. Taking exec_queue.lock here causes undue dependency
+	 * on vm->lock taken during xe_exec_queue_kill().
+	 */
 	xa_for_each(&xef->exec_queue.xa, idx, q) {
 		xe_exec_queue_kill(q);
 		xe_exec_queue_put(q);
 	}
-	mutex_unlock(&xef->exec_queue.lock);
 	xa_destroy(&xef->exec_queue.xa);
 	mutex_destroy(&xef->exec_queue.lock);
 	mutex_lock(&xef->vm.lock);
-- 
2.43.0


^ permalink raw reply related	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2024-05-30  1:26 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz follow: Atom feed
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2024-05-29 21:39 [PATCH v3] drm/xe: Remove unwanted mutex locking Niranjana Vishwanathapura
2024-05-29 21:45 ` ✓ CI.Patch_applied: success for drm/xe: Remove unwanted mutex locking (rev3) Patchwork
2024-05-29 21:45 ` ✓ CI.checkpatch: " Patchwork
2024-05-29 21:46 ` ✓ CI.KUnit: " Patchwork
2024-05-29 21:58 ` ✓ CI.Build: " Patchwork
2024-05-29 21:58 ` ✗ CI.Hooks: failure " Patchwork
2024-05-29 21:59 ` [PATCH v3] drm/xe: Remove unwanted mutex locking Rodrigo Vivi
2024-05-29 21:59 ` ✓ CI.checksparse: success for drm/xe: Remove unwanted mutex locking (rev3) Patchwork
2024-05-29 22:32 ` ✓ CI.BAT: " Patchwork
2024-05-30  1:26 ` ✓ CI.FULL: " Patchwork

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