From 6c7c8fb863f7c3137ce5fc4b435af3891083abeb Mon Sep 17 00:00:00 2001 From: Rob Clark Date: Mon, 20 Mar 2023 07:43:30 -0700 Subject: [PATCH] drm/msm/gem: Protect pin_count/madv by LRU lock Since the LRU lock is already acquired when moving an obj between LRUs, we can use it to protect pin_count and madv, without any significant change in locking (ie. it just expands the scope of the lock by a hand- ful of instructions). This prepares the way to decrement the pin_count in the job_run() path without needing to hold the obj lock, to avoid a potential deadlock (or rather stall) caused by the fence-signaling path (job_run()) blocking on shrinker/reclaim. (Only a stall because the wait for fence signaling wait_for_idle() is not infinite.) Signed-off-by: Rob Clark Patchwork: https://patchwork.freedesktop.org/patch/527843/ Link: https://lore.kernel.org/r/20230320144356.803762-9-robdclark@gmail.com --- drivers/gpu/drm/msm/msm_gem.c | 48 ++++++++++++++++++++++++++++++++----------- drivers/gpu/drm/msm/msm_gem.h | 9 +++++++- 2 files changed, 44 insertions(+), 13 deletions(-) diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c index 58ac945..b9171ac 100644 --- a/drivers/gpu/drm/msm/msm_gem.c +++ b/drivers/gpu/drm/msm/msm_gem.c @@ -61,7 +61,7 @@ static void sync_for_cpu(struct msm_gem_object *msm_obj) dma_unmap_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL, 0); } -static void update_lru(struct drm_gem_object *obj) +static void update_lru_locked(struct drm_gem_object *obj) { struct msm_drm_private *priv = obj->dev->dev_private; struct msm_gem_object *msm_obj = to_msm_bo(obj); @@ -71,18 +71,27 @@ static void update_lru(struct drm_gem_object *obj) if (!msm_obj->pages) { GEM_WARN_ON(msm_obj->pin_count); - drm_gem_lru_move_tail(&priv->lru.unbacked, obj); + drm_gem_lru_move_tail_locked(&priv->lru.unbacked, obj); } else if (msm_obj->pin_count) { - drm_gem_lru_move_tail(&priv->lru.pinned, obj); + drm_gem_lru_move_tail_locked(&priv->lru.pinned, obj); } else if (msm_obj->madv == MSM_MADV_WILLNEED) { - drm_gem_lru_move_tail(&priv->lru.willneed, obj); + drm_gem_lru_move_tail_locked(&priv->lru.willneed, obj); } else { GEM_WARN_ON(msm_obj->madv != MSM_MADV_DONTNEED); - drm_gem_lru_move_tail(&priv->lru.dontneed, obj); + drm_gem_lru_move_tail_locked(&priv->lru.dontneed, obj); } } +static void update_lru(struct drm_gem_object *obj) +{ + struct msm_drm_private *priv = obj->dev->dev_private; + + mutex_lock(&priv->lru.lock); + update_lru_locked(obj); + mutex_unlock(&priv->lru.lock); +} + /* allocate pages from VRAM carveout, used when no IOMMU: */ static struct page **get_pages_vram(struct drm_gem_object *obj, int npages) { @@ -200,6 +209,7 @@ static void put_pages(struct drm_gem_object *obj) static struct page **msm_gem_pin_pages_locked(struct drm_gem_object *obj) { + struct msm_drm_private *priv = obj->dev->dev_private; struct msm_gem_object *msm_obj = to_msm_bo(obj); struct page **p; @@ -210,10 +220,13 @@ static struct page **msm_gem_pin_pages_locked(struct drm_gem_object *obj) } p = get_pages(obj); - if (!IS_ERR(p)) { - to_msm_bo(obj)->pin_count++; - update_lru(obj); - } + if (IS_ERR(p)) + return p; + + mutex_lock(&priv->lru.lock); + msm_obj->pin_count++; + update_lru_locked(obj); + mutex_unlock(&priv->lru.lock); return p; } @@ -464,14 +477,16 @@ int msm_gem_pin_vma_locked(struct drm_gem_object *obj, struct msm_gem_vma *vma) void msm_gem_unpin_locked(struct drm_gem_object *obj) { + struct msm_drm_private *priv = obj->dev->dev_private; struct msm_gem_object *msm_obj = to_msm_bo(obj); msm_gem_assert_locked(obj); + mutex_lock(&priv->lru.lock); msm_obj->pin_count--; GEM_WARN_ON(msm_obj->pin_count < 0); - - update_lru(obj); + update_lru_locked(obj); + mutex_unlock(&priv->lru.lock); } struct msm_gem_vma *msm_gem_get_vma_locked(struct drm_gem_object *obj, @@ -739,10 +754,13 @@ void msm_gem_put_vaddr(struct drm_gem_object *obj) */ int msm_gem_madvise(struct drm_gem_object *obj, unsigned madv) { + struct msm_drm_private *priv = obj->dev->dev_private; struct msm_gem_object *msm_obj = to_msm_bo(obj); msm_gem_lock(obj); + mutex_lock(&priv->lru.lock); + if (msm_obj->madv != __MSM_MADV_PURGED) msm_obj->madv = madv; @@ -751,7 +769,9 @@ int msm_gem_madvise(struct drm_gem_object *obj, unsigned madv) /* If the obj is inactive, we might need to move it * between inactive lists */ - update_lru(obj); + update_lru_locked(obj); + + mutex_unlock(&priv->lru.lock); msm_gem_unlock(obj); @@ -761,6 +781,7 @@ int msm_gem_madvise(struct drm_gem_object *obj, unsigned madv) void msm_gem_purge(struct drm_gem_object *obj) { struct drm_device *dev = obj->dev; + struct msm_drm_private *priv = obj->dev->dev_private; struct msm_gem_object *msm_obj = to_msm_bo(obj); msm_gem_assert_locked(obj); @@ -777,7 +798,10 @@ void msm_gem_purge(struct drm_gem_object *obj) put_iova_vmas(obj); + mutex_lock(&priv->lru.lock); + /* A one-way transition: */ msm_obj->madv = __MSM_MADV_PURGED; + mutex_unlock(&priv->lru.lock); drm_gem_free_mmap_offset(obj); diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h index 1929f09..0057e8e 100644 --- a/drivers/gpu/drm/msm/msm_gem.h +++ b/drivers/gpu/drm/msm/msm_gem.h @@ -86,7 +86,9 @@ struct msm_gem_object { uint32_t flags; /** - * Advice: are the backing pages purgeable? + * madv: are the backing pages purgeable? + * + * Protected by obj lock and LRU lock */ uint8_t madv; @@ -114,6 +116,11 @@ struct msm_gem_object { char name[32]; /* Identifier to print for the debugfs files */ + /** + * pin_count: Number of times the pages are pinned + * + * Protected by LRU lock. + */ int pin_count; }; #define to_msm_bo(x) container_of(x, struct msm_gem_object, base) -- 2.7.4