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drm/xe: Remove unwanted mutex locking

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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)
v4: Further expand code comment (Rodirgo 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>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240529221639.23117-1-niranjana.vishwanathapura@intel.com
This commit is contained in:
Niranjana Vishwanathapura 2024-05-29 15:16:39 -07:00 committed by Matthew Brost
parent 37ea1aee18
commit 0568a4086a
1 changed files with 6 additions and 2 deletions
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8
drivers/gpu/drm/xe/xe_device.c
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@ -95,12 +95,16 @@ 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 for it
* when FD is closing as IOCTLs presumably can't be modifying the
* xarray. 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);