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Commit 96726fe5 authored by Thomas Hellstrom's avatar Thomas Hellstrom Committed by Dave Airlie
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drm/ttm: Don't deadlock on recursive multi-bo reservations 



Add an aid for the driver to detect deadlocks on multi-bo reservations
Update documentation.

Signed-off-by: default avatarThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: default avatarJerome Glisse <j.glisse@gmail.com>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 68c4fa31

drivers/gpu/drm/ttm/ttm_bo.c

+12 −3
Original line number Diff line number Diff line
@@ -223,8 +223,17 @@ int ttm_bo_reserve_locked(struct ttm_buffer_object *bo, 
		/**

		 * Deadlock avoidance for multi-bo reserving.

		 */

		if (use_sequence && bo->seq_valid &&

			(sequence - bo->val_seq < (1 << 31))) {

		if (use_sequence && bo->seq_valid) {

			/**

			 * We've already reserved this one.

			 */

			if (unlikely(sequence == bo->val_seq))

				return -EDEADLK;

			/**

			 * Already reserved by a thread that will not back

			 * off for us. We need to back off.

			 */

			if (unlikely(sequence - bo->val_seq < (1 << 31)))

				return -EAGAIN;

		}

include/drm/ttm/ttm_bo_driver.h

+22 −3
Original line number Diff line number Diff line
@@ -859,6 +859,9 @@ extern void ttm_bo_unmap_virtual(struct ttm_buffer_object *bo); 
 * try again. (only if use_sequence == 1).

 * -ERESTARTSYS: A wait for the buffer to become unreserved was interrupted by

 * a signal. Release all buffer reservations and return to user-space.

 * -EBUSY: The function needed to sleep, but @no_wait was true

 * -EDEADLK: Bo already reserved using @sequence. This error code will only

 * be returned if @use_sequence is set to true.

 */

extern int ttm_bo_reserve(struct ttm_buffer_object *bo,

			  bool interruptible,
@@ -868,11 +871,27 @@ extern int ttm_bo_reserve(struct ttm_buffer_object *bo, 
/**

 * ttm_bo_reserve_locked:

 *

 * Similar to ttm_bo_reserve, but must be called with the glob::lru_lock

 * spinlock held, and will not remove reserved buffers from the lru lists.

 * @bo: A pointer to a struct ttm_buffer_object.

 * @interruptible: Sleep interruptible if waiting.

 * @no_wait: Don't sleep while trying to reserve, rather return -EBUSY.

 * @use_sequence: If @bo is already reserved, Only sleep waiting for

 * it to become unreserved if @sequence < (@bo)->sequence.

 *

 * Must be called with struct ttm_bo_global::lru_lock held,

 * and will not remove reserved buffers from the lru lists.

 * The function may release the LRU spinlock if it needs to sleep.

 * Otherwise identical to ttm_bo_reserve.

 *

 * Returns:

 * -EAGAIN: The reservation may cause a deadlock.

 * Release all buffer reservations, wait for @bo to become unreserved and

 * try again. (only if use_sequence == 1).

 * -ERESTARTSYS: A wait for the buffer to become unreserved was interrupted by

 * a signal. Release all buffer reservations and return to user-space.

 * -EBUSY: The function needed to sleep, but @no_wait was true

 * -EDEADLK: Bo already reserved using @sequence. This error code will only

 * be returned if @use_sequence is set to true.

 */



extern int ttm_bo_reserve_locked(struct ttm_buffer_object *bo,

				 bool interruptible,

				 bool no_wait, bool use_sequence,