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drm/panfrost: Use mutex_trylock in panfrost_gem_purge

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Lockdep reports a circular locking dependency with pages_lock taken in
the shrinker callback. The deadlock can't actually happen with current
users at least as a BO will never be purgeable when pages_lock is held.
To be safe, let's use mutex_trylock() instead and bail if a BO is locked
already.

Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Steven Price <steven.price@arm.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190823021216.5862-7-robh@kernel.org
This commit is contained in:
Rob Herring 2019-08-22 21:12:14 -05:00
parent dfbc7a46b9
commit ce49324261
1 changed files with 7 additions and 4 deletions
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11
drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
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@ -36,15 +36,18 @@ panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc
return count;
}
static void panfrost_gem_purge(struct drm_gem_object *obj)
static bool panfrost_gem_purge(struct drm_gem_object *obj)
{
struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
mutex_lock(&shmem->pages_lock);
if (!mutex_trylock(&shmem->pages_lock))
return false;
panfrost_mmu_unmap(to_panfrost_bo(obj));
drm_gem_shmem_purge_locked(obj);
mutex_unlock(&shmem->pages_lock);
return true;
}
static unsigned long
@ -61,8 +64,8 @@ panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
if (freed >= sc->nr_to_scan)
break;
if (drm_gem_shmem_is_purgeable(shmem)) {
panfrost_gem_purge(&shmem->base);
if (drm_gem_shmem_is_purgeable(shmem) &&
panfrost_gem_purge(&shmem->base)) {
freed += shmem->base.size >> PAGE_SHIFT;
list_del_init(&shmem->madv_list);
}