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drm/ttm: remove lru_lock around ttm_bo_reserve

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There should no longer be assumptions that reserve will always succeed
with the lru lock held, so we can safely break the whole atomic
reserve/lru thing. As a bonus this fixes most lockdep annotations for
reservations.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
This commit is contained in:
Maarten Lankhorst
2013-01-15 14:56:37 +01:00
parent 979ee290ff
commit 63d0a41955
3 changed files with 40 additions and 35 deletions
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19
include/drm/ttm/ttm_bo_driver.h
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@@ -790,16 +790,7 @@ extern void ttm_mem_io_unlock(struct ttm_mem_type_manager *man);
* to make room for a buffer already reserved. (Buffers are reserved before
* they are evicted). The following algorithm prevents such deadlocks from
* occurring:
* 1) Buffers are reserved with the lru spinlock held. Upon successful
* reservation they are removed from the lru list. This stops a reserved buffer
* from being evicted. However the lru spinlock is released between the time
* a buffer is selected for eviction and the time it is reserved.
* Therefore a check is made when a buffer is reserved for eviction, that it
* is still the first buffer in the lru list, before it is removed from the
* list. @check_lru == 1 forces this check. If it fails, the function returns
* -EINVAL, and the caller should then choose a new buffer to evict and repeat
* the procedure.
* 2) Processes attempting to reserve multiple buffers other than for eviction,
* Processes attempting to reserve multiple buffers other than for eviction,
* (typically execbuf), should first obtain a unique 32-bit
* validation sequence number,
* and call this function with @use_sequence == 1 and @sequence == the unique
@@ -832,7 +823,7 @@ extern int ttm_bo_reserve(struct ttm_buffer_object *bo,
/**
* ttm_bo_reserve_locked:
* ttm_bo_reserve_nolru:
*
* @bo: A pointer to a struct ttm_buffer_object.
* @interruptible: Sleep interruptible if waiting.
@@ -840,9 +831,7 @@ extern int ttm_bo_reserve(struct ttm_buffer_object *bo,
* @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.
* Will not remove reserved buffers from the lru lists.
* Otherwise identical to ttm_bo_reserve.
*
* Returns:
@@ -855,7 +844,7 @@ extern int ttm_bo_reserve(struct ttm_buffer_object *bo,
* -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,
extern int ttm_bo_reserve_nolru(struct ttm_buffer_object *bo,
bool interruptible,
bool no_wait, bool use_sequence,
uint32_t sequence);