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drm/msm/gem: Protect pin_count/madv by LRU lock

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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 <robdclark@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/527843/
Link: https://lore.kernel.org/r/20230320144356.803762-9-robdclark@gmail.com
This commit is contained in:
Rob Clark 2023-03-20 07:43:30 -07:00
parent 4a02a376cb
commit 6c7c8fb863
2 changed files with 44 additions and 13 deletions
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48
drivers/gpu/drm/msm/msm_gem.c
View File

@ -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);

9
drivers/gpu/drm/msm/msm_gem.h
View File

@ -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)