[PATCH 04/10] drm/ttm: change fence_lock to inner lock, v3
Thomas Hellstrom
thellstrom at vmware.com
Mon Nov 19 06:17:45 PST 2012
Hi,
This patch looks mostly good, although I think ttm_bo_cleanup_refs
becomes overly complicated:
Could this do, or am I missing something?
static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
bool interruptible,
bool no_wait_reserve,
bool no_wait_gpu)
{
struct ttm_bo_device *bdev = bo->bdev;
struct ttm_bo_global *glob = bo->glob;
int put_count;
int ret = 0;
/*
* First, reserve while making sure we're still on the
* ddestroy list.
*/
retry_reserve:
spin_lock(&glob->lru_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);
spin_lock(&bdev->fence_lock);
ret = ttm_bo_wait(bo, false, interruptible, no_wait_gpu);
spin_unlock(&bdev->fence_lock);
if (unlikely(ret != 0)) {
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);
list_del_init(&bo->ddestroy);
++put_count;
spin_unlock(&glob->lru_lock);
ttm_bo_cleanup_memtype_use(bo);
atomic_set(&bo_reserved, 0);
wake_up_all(&bo->event_queue);
ttm_bo_list_ref_sub(bo, put_count, true);
return 0;
}
On 11/12/2012 03:00 PM, Maarten Lankhorst wrote:
> I changed the hierarchy to make fence_lock the most inner lock,
> instead of outer lock. This will simplify things slightly, and
> hopefully makes it easier to make fence_lock global at one point
> should it be needed.
>
> To make things clearer, I change the order around in ttm_bo_cleanup_refs
> and ttm_bo_cleanup_refs_or_queue.
>
> A reservation is taken first, then fence lock is taken and a wait is attempted.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at canonical.com>
>
> v2:
> - fix conflict with upstream race fix, simplifies ttm_bo_cleanup_refs
> v3:
> - change removal of fence_lock to making it a inner lock instead
> ---
> drivers/gpu/drm/ttm/ttm_bo.c | 95 ++++++++++++++++------------------
> drivers/gpu/drm/ttm/ttm_execbuf_util.c | 4 +-
> 2 files changed, 48 insertions(+), 51 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index a3383a7..70285ff 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -478,28 +478,26 @@ static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo)
> {
> struct ttm_bo_device *bdev = bo->bdev;
> struct ttm_bo_global *glob = bo->glob;
> - struct ttm_bo_driver *driver;
> + struct ttm_bo_driver *driver = bdev->driver;
> void *sync_obj = NULL;
> int put_count;
> int ret;
>
> - spin_lock(&bdev->fence_lock);
> - (void) ttm_bo_wait(bo, false, false, true);
> - if (!bo->sync_obj) {
> -
> - spin_lock(&glob->lru_lock);
> -
> - /**
> - * Lock inversion between bo:reserve and bdev::fence_lock here,
> - * but that's OK, since we're only trylocking.
> - */
> -
> - ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
> + spin_lock(&glob->lru_lock);
> + ret = ttm_bo_reserve_locked(bo, false, true, false, 0);
> + if (!ret) {
> + spin_lock(&bdev->fence_lock);
> + ret = ttm_bo_wait(bo, false, false, true);
>
> - if (unlikely(ret == -EBUSY))
> + if (unlikely(ret == -EBUSY)) {
> + sync_obj = driver->sync_obj_ref(bo->sync_obj);
> + spin_unlock(&bdev->fence_lock);
> + atomic_set(&bo->reserved, 0);
> + wake_up_all(&bo->event_queue);
> goto queue;
> -
> + }
> spin_unlock(&bdev->fence_lock);
> +
> put_count = ttm_bo_del_from_lru(bo);
>
> atomic_set(&bo->reserved, 0);
> @@ -509,18 +507,11 @@ static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo)
> ttm_bo_list_ref_sub(bo, put_count, true);
>
> return;
> - } else {
> - spin_lock(&glob->lru_lock);
> }
> queue:
> - driver = bdev->driver;
> - if (bo->sync_obj)
> - sync_obj = driver->sync_obj_ref(bo->sync_obj);
> -
> kref_get(&bo->list_kref);
> list_add_tail(&bo->ddestroy, &bdev->ddestroy);
> spin_unlock(&glob->lru_lock);
> - spin_unlock(&bdev->fence_lock);
>
> if (sync_obj) {
> driver->sync_obj_flush(sync_obj);
> @@ -546,54 +537,60 @@ static int ttm_bo_cleanup_refs(struct ttm_buffer_object *bo,
> 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;
> + void *sync_obj;
>
> retry:
> - spin_lock(&bdev->fence_lock);
> - ret = ttm_bo_wait(bo, false, interruptible, no_wait_gpu);
> - spin_unlock(&bdev->fence_lock);
> + spin_lock(&glob->lru_lock);
>
> - if (unlikely(ret != 0))
> - return ret;
> + ret = ttm_bo_reserve_locked(bo, interruptible,
> + no_wait_reserve, false, 0);
>
> -retry_reserve:
> - spin_lock(&glob->lru_lock);
> + if (unlikely(ret)) {
> + spin_unlock(&glob->lru_lock);
> + return ret;
> + }
>
> if (unlikely(list_empty(&bo->ddestroy))) {
> + atomic_set(&bo->reserved, 0);
> + wake_up_all(&bo->event_queue);
> 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))
> + spin_lock(&bdev->fence_lock);
> + ret = ttm_bo_wait(bo, false, false, true);
> + if (ret) {
> + if (no_wait_gpu) {
> + spin_unlock(&bdev->fence_lock);
> + atomic_set(&bo->reserved, 0);
> + wake_up_all(&bo->event_queue);
> + spin_unlock(&glob->lru_lock);
> 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.
> - */
> + /**
> + * Take a reference to the fence and unreserve, if the wait
> + * was succesful and no new sync_obj was attached,
> + * ttm_bo_wait in retry will return ret = 0, and end the loop.
> + */
>
> - if (unlikely(bo->sync_obj)) {
> + sync_obj = driver->sync_obj_ref(&bo->sync_obj);
> + spin_unlock(&bdev->fence_lock);
> atomic_set(&bo->reserved, 0);
> wake_up_all(&bo->event_queue);
> spin_unlock(&glob->lru_lock);
> +
> + ret = driver->sync_obj_wait(bo->sync_obj, false, interruptible);
> + driver->sync_obj_unref(&sync_obj);
> + if (ret)
> + return ret;
> goto retry;
> }
> + spin_unlock(&bdev->fence_lock);
>
> put_count = ttm_bo_del_from_lru(bo);
> list_del_init(&bo->ddestroy);
> diff --git a/drivers/gpu/drm/ttm/ttm_execbuf_util.c b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> index 1986d00..cd9e452 100644
> --- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> @@ -213,8 +213,8 @@ void ttm_eu_fence_buffer_objects(struct list_head *list, void *sync_obj)
> driver = bdev->driver;
> glob = bo->glob;
>
> - spin_lock(&bdev->fence_lock);
> spin_lock(&glob->lru_lock);
> + spin_lock(&bdev->fence_lock);
>
> list_for_each_entry(entry, list, head) {
> bo = entry->bo;
> @@ -223,8 +223,8 @@ void ttm_eu_fence_buffer_objects(struct list_head *list, void *sync_obj)
> ttm_bo_unreserve_locked(bo);
> entry->reserved = false;
> }
> - spin_unlock(&glob->lru_lock);
> spin_unlock(&bdev->fence_lock);
> + spin_unlock(&glob->lru_lock);
>
> list_for_each_entry(entry, list, head) {
> if (entry->old_sync_obj)
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