From 63d0a4195560362e2e00a3ad38fc331d34e1da9b Mon Sep 17 00:00:00 2001 From: Maarten Lankhorst Date: Tue, 15 Jan 2013 14:56:37 +0100 Subject: drm/ttm: remove lru_lock around ttm_bo_reserve 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 Reviewed-by: Jerome Glisse --- include/drm/ttm/ttm_bo_driver.h | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-) (limited to 'include/drm') diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h index e3a43a47d78c..6fff43222e20 100644 --- a/include/drm/ttm/ttm_bo_driver.h +++ b/include/drm/ttm/ttm_bo_driver.h @@ -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); -- cgit v1.2.3 From 5e45d7dfd74100d622f9cdc70bfd1f9fae1671de Mon Sep 17 00:00:00 2001 From: Maarten Lankhorst Date: Tue, 15 Jan 2013 14:57:05 +0100 Subject: drm/ttm: add ttm_bo_reserve_slowpath Instead of dropping everything, waiting for the bo to be unreserved and trying over, a better strategy would be to do a blocking wait. This can be mapped a lot better to a mutex_lock-like call. Signed-off-by: Maarten Lankhorst Reviewed-by: Jerome Glisse --- drivers/gpu/drm/ttm/ttm_bo.c | 47 +++++++++++++++++++++++++++++++++++++++++ include/drm/ttm/ttm_bo_driver.h | 30 ++++++++++++++++++++++++++ 2 files changed, 77 insertions(+) (limited to 'include/drm') diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index e8e4814b1295..4dd6f9e77a7d 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -310,6 +310,53 @@ int ttm_bo_reserve(struct ttm_buffer_object *bo, return ret; } +int ttm_bo_reserve_slowpath_nolru(struct ttm_buffer_object *bo, + bool interruptible, uint32_t sequence) +{ + bool wake_up = false; + int ret; + + while (unlikely(atomic_xchg(&bo->reserved, 1) != 0)) { + WARN_ON(bo->seq_valid && sequence == bo->val_seq); + + ret = ttm_bo_wait_unreserved(bo, interruptible); + + if (unlikely(ret)) + return ret; + } + + if ((bo->val_seq - sequence < (1 << 31)) || !bo->seq_valid) + wake_up = true; + + /** + * Wake up waiters that may need to recheck for deadlock, + * if we decreased the sequence number. + */ + bo->val_seq = sequence; + bo->seq_valid = true; + if (wake_up) + wake_up_all(&bo->event_queue); + + return 0; +} + +int ttm_bo_reserve_slowpath(struct ttm_buffer_object *bo, + bool interruptible, uint32_t sequence) +{ + struct ttm_bo_global *glob = bo->glob; + int put_count, ret; + + ret = ttm_bo_reserve_slowpath_nolru(bo, interruptible, sequence); + if (likely(!ret)) { + spin_lock(&glob->lru_lock); + put_count = ttm_bo_del_from_lru(bo); + spin_unlock(&glob->lru_lock); + ttm_bo_list_ref_sub(bo, put_count, true); + } + return ret; +} +EXPORT_SYMBOL(ttm_bo_reserve_slowpath); + void ttm_bo_unreserve_locked(struct ttm_buffer_object *bo) { ttm_bo_add_to_lru(bo); diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h index 6fff43222e20..5af71af6bf88 100644 --- a/include/drm/ttm/ttm_bo_driver.h +++ b/include/drm/ttm/ttm_bo_driver.h @@ -821,6 +821,36 @@ extern int ttm_bo_reserve(struct ttm_buffer_object *bo, bool interruptible, bool no_wait, bool use_sequence, uint32_t sequence); +/** + * ttm_bo_reserve_slowpath_nolru: + * @bo: A pointer to a struct ttm_buffer_object. + * @interruptible: Sleep interruptible if waiting. + * @sequence: Set (@bo)->sequence to this value after lock + * + * This is called after ttm_bo_reserve returns -EAGAIN and we backed off + * from all our other reservations. Because there are no other reservations + * held by us, this function cannot deadlock any more. + * + * Will not remove reserved buffers from the lru lists. + * Otherwise identical to ttm_bo_reserve_slowpath. + */ +extern int ttm_bo_reserve_slowpath_nolru(struct ttm_buffer_object *bo, + bool interruptible, + uint32_t sequence); + + +/** + * ttm_bo_reserve_slowpath: + * @bo: A pointer to a struct ttm_buffer_object. + * @interruptible: Sleep interruptible if waiting. + * @sequence: Set (@bo)->sequence to this value after lock + * + * This is called after ttm_bo_reserve returns -EAGAIN and we backed off + * from all our other reservations. Because there are no other reservations + * held by us, this function cannot deadlock any more. + */ +extern int ttm_bo_reserve_slowpath(struct ttm_buffer_object *bo, + bool interruptible, uint32_t sequence); /** * ttm_bo_reserve_nolru: -- cgit v1.2.3 From cc4c0c4de3c775be22072ec3251f2e581b63d9a0 Mon Sep 17 00:00:00 2001 From: Maarten Lankhorst Date: Tue, 15 Jan 2013 14:57:28 +0100 Subject: drm/ttm: unexport ttm_bo_wait_unreserved All legitimate users of this function outside ttm_bo.c are gone, now it's only an implementation detail. Signed-off-by: Maarten Lankhorst Reviewed-by: Jerome Glisse --- drivers/gpu/drm/ttm/ttm_bo.c | 4 ++-- include/drm/ttm/ttm_bo_driver.h | 12 ------------ 2 files changed, 2 insertions(+), 14 deletions(-) (limited to 'include/drm') diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index 4dd6f9e77a7d..4df47f72214a 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -158,7 +158,8 @@ static void ttm_bo_release_list(struct kref *list_kref) ttm_mem_global_free(bdev->glob->mem_glob, acc_size); } -int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo, bool interruptible) +static int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo, + bool interruptible) { if (interruptible) { return wait_event_interruptible(bo->event_queue, @@ -168,7 +169,6 @@ int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo, bool interruptible) return 0; } } -EXPORT_SYMBOL(ttm_bo_wait_unreserved); void ttm_bo_add_to_lru(struct ttm_buffer_object *bo) { diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h index 5af71af6bf88..0fbd046e7c93 100644 --- a/include/drm/ttm/ttm_bo_driver.h +++ b/include/drm/ttm/ttm_bo_driver.h @@ -898,18 +898,6 @@ extern void ttm_bo_unreserve(struct ttm_buffer_object *bo); */ extern void ttm_bo_unreserve_locked(struct ttm_buffer_object *bo); -/** - * ttm_bo_wait_unreserved - * - * @bo: A pointer to a struct ttm_buffer_object. - * - * Wait for a struct ttm_buffer_object to become unreserved. - * This is typically used in the execbuf code to relax cpu-usage when - * a potential deadlock condition backoff. - */ -extern int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo, - bool interruptible); - /* * ttm_bo_util.c */ -- cgit v1.2.3