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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: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jerome Glisse <j.glisse@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Thomas Hellstrom 2010-11-17 12:28:28 +00:00 committed by Dave Airlie
parent 68c4fa31aa
commit 96726fe50f
2 changed files with 34 additions and 6 deletions
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13
drivers/gpu/drm/ttm/ttm_bo.c
View File

@ -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;
}

25
include/drm/ttm/ttm_bo_driver.h
View File

@ -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,