From 02070f04987524caf77d4bf4c94ebceb783b7bcc Mon Sep 17 00:00:00 2001 From: Rob Clark Date: Sun, 29 Jun 2025 13:12:46 -0700 Subject: [PATCH 4307/5403] drm/gem: Add ww_acquire_ctx support to drm_gem_lru_scan() If the callback is going to have to attempt to grab more locks, it is useful to have an ww_acquire_ctx to avoid locking order problems. Why not use the drm_exec helper instead? Mainly because (a) where ww_acquire_init() is called is awkward, and (b) we don't really need to retry after backoff, we can just move on to the next object. Signed-off-by: Rob Clark Signed-off-by: Rob Clark Tested-by: Antonino Maniscalco Reviewed-by: Antonino Maniscalco Patchwork: https://patchwork.freedesktop.org/patch/661463/ --- drivers/gpu/drm/drm_gem.c | 14 +++++++++++--- include/drm/drm_gem.h | 10 ++++++---- 2 files changed, 17 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index 19d50d254fe6..0905ef6786e9 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -1429,12 +1429,14 @@ EXPORT_SYMBOL(drm_gem_lru_move_tail); * @nr_to_scan: The number of pages to try to reclaim * @remaining: The number of pages left to reclaim, should be initialized by caller * @shrink: Callback to try to shrink/reclaim the object. + * @ticket: Optional ww_acquire_ctx context to use for locking */ unsigned long drm_gem_lru_scan(struct drm_gem_lru *lru, unsigned int nr_to_scan, unsigned long *remaining, - bool (*shrink)(struct drm_gem_object *obj)) + bool (*shrink)(struct drm_gem_object *obj, struct ww_acquire_ctx *ticket), + struct ww_acquire_ctx *ticket) { struct drm_gem_lru still_in_lru; struct drm_gem_object *obj; @@ -1467,17 +1469,20 @@ drm_gem_lru_scan(struct drm_gem_lru *lru, */ mutex_unlock(lru->lock); + if (ticket) + ww_acquire_init(ticket, &reservation_ww_class); + /* * Note that this still needs to be trylock, since we can * hit shrinker in response to trying to get backing pages * for this obj (ie. while it's lock is already held) */ - if (!dma_resv_trylock(obj->resv)) { + if (!ww_mutex_trylock(&obj->resv->lock, ticket)) { *remaining += obj->size >> PAGE_SHIFT; goto tail; } - if (shrink(obj)) { + if (shrink(obj, ticket)) { freed += obj->size >> PAGE_SHIFT; /* @@ -1491,6 +1496,9 @@ drm_gem_lru_scan(struct drm_gem_lru *lru, dma_resv_unlock(obj->resv); + if (ticket) + ww_acquire_fini(ticket); + tail: drm_gem_object_put(obj); mutex_lock(lru->lock); diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h index 1a79ec3fe45c..d3a7b43e2c63 100644 --- a/include/drm/drm_gem.h +++ b/include/drm/drm_gem.h @@ -560,10 +560,12 @@ void drm_gem_lru_init(struct drm_gem_lru *lru, struct mutex *lock); void drm_gem_lru_remove(struct drm_gem_object *obj); void drm_gem_lru_move_tail_locked(struct drm_gem_lru *lru, struct drm_gem_object *obj); void drm_gem_lru_move_tail(struct drm_gem_lru *lru, struct drm_gem_object *obj); -unsigned long drm_gem_lru_scan(struct drm_gem_lru *lru, - unsigned int nr_to_scan, - unsigned long *remaining, - bool (*shrink)(struct drm_gem_object *obj)); +unsigned long +drm_gem_lru_scan(struct drm_gem_lru *lru, + unsigned int nr_to_scan, + unsigned long *remaining, + bool (*shrink)(struct drm_gem_object *obj, struct ww_acquire_ctx *ticket), + struct ww_acquire_ctx *ticket); int drm_gem_evict_locked(struct drm_gem_object *obj); -- 2.54.0