[PATCH] drm/xe: Move VM dma-resv lock from xe_exec_queue_create to __xe_exec_queue_init

[Matthew Brost]

The critical section which requires the VM dma-resv is the call
xe_lrc_create in __xe_exec_queue_init. Move this lock to
__xe_exec_queue_init holding it just around xe_lrc_create. Not only is
good practice, this also fixes a locking double of the VM dma-resv in
the error paths of __xe_exec_queue_init as xe_lrc_put tries to acquire
this too resulting in a deadlock.

Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Signed-off-by: Matthw Brost <matthew.brost at intel.com>
---
 drivers/gpu/drm/xe/xe_exec_queue.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
index 69867a7b7c77..0d72846af9bf 100644
--- a/drivers/gpu/drm/xe/xe_exec_queue.c
+++ b/drivers/gpu/drm/xe/xe_exec_queue.c
@@ -105,22 +105,35 @@ static struct xe_exec_queue *__xe_exec_queue_alloc(struct xe_device *xe,
 
 static int __xe_exec_queue_init(struct xe_exec_queue *q)
 {
+	struct xe_vm *vm = q->vm;
 	int i, err;
 
+	if (vm) {
+		err = xe_vm_lock(vm, true);
+		if (err)
+			return err;
+	}
+
 	for (i = 0; i < q->width; ++i) {
 		q->lrc[i] = xe_lrc_create(q->hwe, q->vm, SZ_16K);
 		if (IS_ERR(q->lrc[i])) {
 			err = PTR_ERR(q->lrc[i]);
-			goto err_lrc;
+			goto err_unlock;
 		}
 	}
 
+	if (vm)
+		xe_vm_unlock(vm);
+
 	err = q->ops->init(q);
 	if (err)
 		goto err_lrc;
 
 	return 0;
 
+err_unlock:
+	if (vm)
+		xe_vm_unlock(vm);
 err_lrc:
 	for (i = i - 1; i >= 0; --i)
 		xe_lrc_put(q->lrc[i]);
@@ -140,15 +153,7 @@ struct xe_exec_queue *xe_exec_queue_create(struct xe_device *xe, struct xe_vm *v
 	if (IS_ERR(q))
 		return q;
 
-	if (vm) {
-		err = xe_vm_lock(vm, true);
-		if (err)
-			goto err_post_alloc;
-	}
-
 	err = __xe_exec_queue_init(q);
-	if (vm)
-		xe_vm_unlock(vm);
 	if (err)
 		goto err_post_alloc;
 
-- 
2.34.1