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drm/ttm: call ttm_bo_cleanup_refs with reservation and lru lock held, v3

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By removing the unlocking of lru and retaking it immediately, a race is
removed where the bo is taken off the swap list or the lru list between
the unlock and relock. As such the cleanup_refs code can be simplified,
it will attempt to call ttm_bo_wait non-blockingly, and if it fails
it will drop the locks and perform a blocking wait, or return an error
if no_wait_gpu was set.

The need for looping is also eliminated, since swapout and evict_mem_first
will always follow the destruction path, no new fence is allowed
to be attached. As far as I can see this may already have been the case,
but the unlocking / relocking required a complicated loop to deal with
re-reservation.

Changes since v1:
 - Simplify no_wait_gpu case by folding it in with empty ddestroy.
 - Hold a reservation while calling ttm_bo_cleanup_memtype_use again.
Changes since v2:
 - Do not remove bo from lru list while waiting

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Maarten Lankhorst 2012-11-29 11:36:54 +00:00 committed by Dave Airlie
parent 6ed9ccb412
commit 85b144f860
1 changed files with 83 additions and 54 deletions
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137
drivers/gpu/drm/ttm/ttm_bo.c
View file

@ -488,12 +488,16 @@ static void ttm_bo_cleanup_memtype_use(struct ttm_buffer_object *bo)
ttm_bo_mem_put(bo, &bo->mem);
atomic_set(&bo->reserved, 0);
wake_up_all(&bo->event_queue);
/*
* Make processes trying to reserve really pick it up.
* Since the final reference to this bo may not be dropped by
* the current task we have to put a memory barrier here to make
* sure the changes done in this function are always visible.
*
* This function only needs protection against the final kref_put.
*/
smp_mb__after_atomic_dec();
wake_up_all(&bo->event_queue);
smp_mb__before_atomic_dec();
}
static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo)
@ -543,68 +547,84 @@ static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo)
}
/**
* function ttm_bo_cleanup_refs
* function ttm_bo_cleanup_refs_and_unlock
* If bo idle, remove from delayed- and lru lists, and unref.
* If not idle, do nothing.
*
* Must be called with lru_lock and reservation held, this function
* will drop both before returning.
*
* @interruptible Any sleeps should occur interruptibly.
* @no_wait_reserve Never wait for reserve. Return -EBUSY instead.
* @no_wait_gpu Never wait for gpu. Return -EBUSY instead.
*/
static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
bool interruptible,
bool no_wait_reserve,
bool no_wait_gpu)
static int ttm_bo_cleanup_refs_and_unlock(struct ttm_buffer_object *bo,
bool interruptible,
bool no_wait_gpu)
{
struct ttm_bo_device *bdev = bo->bdev;
struct ttm_bo_driver *driver = bdev->driver;
struct ttm_bo_global *glob = bo->glob;
int put_count;
int ret = 0;
int ret;
retry:
spin_lock(&bdev->fence_lock);
ret = ttm_bo_wait(bo, false, interruptible, no_wait_gpu);
spin_unlock(&bdev->fence_lock);
ret = ttm_bo_wait(bo, false, false, true);
if (unlikely(ret != 0))
return ret;
if (ret && !no_wait_gpu) {
void *sync_obj;
retry_reserve:
spin_lock(&glob->lru_lock);
/*
* Take a reference to the fence and unreserve,
* at this point the buffer should be dead, so
* no new sync objects can be attached.
*/
sync_obj = driver->sync_obj_ref(&bo->sync_obj);
spin_unlock(&bdev->fence_lock);
if (unlikely(list_empty(&bo->ddestroy))) {
spin_unlock(&glob->lru_lock);
return 0;
}
ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
if (unlikely(ret == -EBUSY)) {
spin_unlock(&glob->lru_lock);
if (likely(!no_wait_reserve))
ret = ttm_bo_wait_unreserved(bo, interruptible);
if (unlikely(ret != 0))
return ret;
goto retry_reserve;
}
BUG_ON(ret != 0);
/**
* We can re-check for sync object without taking
* the bo::lock since setting the sync object requires
* also bo::reserved. A busy object at this point may
* be caused by another thread recently starting an accelerated
* eviction.
*/
if (unlikely(bo->sync_obj)) {
atomic_set(&bo->reserved, 0);
wake_up_all(&bo->event_queue);
spin_unlock(&glob->lru_lock);
goto retry;
ret = driver->sync_obj_wait(sync_obj, false, interruptible);
driver->sync_obj_unref(&sync_obj);
if (ret)
return ret;
/*
* remove sync_obj with ttm_bo_wait, the wait should be
* finished, and no new wait object should have been added.
*/
spin_lock(&bdev->fence_lock);
ret = ttm_bo_wait(bo, false, false, true);
WARN_ON(ret);
spin_unlock(&bdev->fence_lock);
if (ret)
return ret;
spin_lock(&glob->lru_lock);
ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
/*
* We raced, and lost, someone else holds the reservation now,
* and is probably busy in ttm_bo_cleanup_memtype_use.
*
* Even if it's not the case, because we finished waiting any
* delayed destruction would succeed, so just return success
* here.
*/
if (ret) {
spin_unlock(&glob->lru_lock);
return 0;
}
} else
spin_unlock(&bdev->fence_lock);
if (ret || unlikely(list_empty(&bo->ddestroy))) {
atomic_set(&bo->reserved, 0);
wake_up_all(&bo->event_queue);
spin_unlock(&glob->lru_lock);
return ret;
}
put_count = ttm_bo_del_from_lru(bo);
@ -647,9 +667,13 @@ static int ttm_bo_delayed_delete(struct ttm_bo_device *bdev, bool remove_all)
kref_get(&nentry->list_kref);
}
spin_unlock(&glob->lru_lock);
ret = ttm_bo_cleanup_refs(entry, false, !remove_all,
!remove_all);
ret = ttm_bo_reserve_locked(entry, false, !remove_all, false, 0);
if (!ret)
ret = ttm_bo_cleanup_refs_and_unlock(entry, false,
!remove_all);
else
spin_unlock(&glob->lru_lock);
kref_put(&entry->list_kref, ttm_bo_release_list);
entry = nentry;
@ -800,9 +824,13 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
kref_get(&bo->list_kref);
if (!list_empty(&bo->ddestroy)) {
spin_unlock(&glob->lru_lock);
ret = ttm_bo_cleanup_refs(bo, interruptible,
no_wait_reserve, no_wait_gpu);
ret = ttm_bo_reserve_locked(bo, interruptible, no_wait_reserve, false, 0);
if (!ret)
ret = ttm_bo_cleanup_refs_and_unlock(bo, interruptible,
no_wait_gpu);
else
spin_unlock(&glob->lru_lock);
kref_put(&bo->list_kref, ttm_bo_release_list);
return ret;
@ -1796,8 +1824,9 @@ static int ttm_bo_swapout(struct ttm_mem_shrink *shrink)
kref_get(&bo->list_kref);
if (!list_empty(&bo->ddestroy)) {
spin_unlock(&glob->lru_lock);
(void) ttm_bo_cleanup_refs(bo, false, false, false);
ttm_bo_reserve_locked(bo, false, false, false, 0);
ttm_bo_cleanup_refs_and_unlock(bo, false, false);
kref_put(&bo->list_kref, ttm_bo_release_list);
spin_lock(&glob->lru_lock);
continue;