[PATCH 3/4] drm/panfrost: Fix shrinker lockdep issues using drm_gem_shmem_purge()

From: Rob Herring <robh@kernel.org>
To: dri-devel@lists.freedesktop.org
Cc: Maxime Ripard <maxime.ripard@bootlin.com>,
	Tomeu Vizoso <tomeu.vizoso@collabora.com>,
	David Airlie <airlied@linux.ie>, Sean Paul <sean@poorly.run>,
	Steven Price <steven.price@arm.com>,
	Boris Brezillon <boris.brezillon@collabora.com>,
	Robin Murphy <robin.murphy@arm.com>
Subject: [PATCH 3/4] drm/panfrost: Fix shrinker lockdep issues using drm_gem_shmem_purge()
Date: Mon, 19 Aug 2019 11:12:03 -0500	[thread overview]
Message-ID: <20190819161204.3106-4-robh@kernel.org> (raw)
In-Reply-To: <20190819161204.3106-1-robh@kernel.org>

This fixes 2 issues found by lockdep. First, drm_gem_shmem_purge()
now uses mutex_trylock for the pages_lock to avoid a circular
dependency.

Second, it drops the call to panfrost_mmu_unmap() which takes several
locks due to runtime PM calls. The call is not necessary because the
unmapping is also called in panfrost_gem_close() already.

Fixes: 013b65101315 ("drm/panfrost: Add madvise and shrinker support")
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>
---
 drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
index d191632b6197..cc15005dc68f 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
@@ -36,17 +36,6 @@ panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc
 	return count;
 }
 
-static void 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);
-
-	panfrost_mmu_unmap(to_panfrost_bo(obj));
-	drm_gem_shmem_purge_locked(obj);
-
-	mutex_unlock(&shmem->pages_lock);
-}
-
 static unsigned long
 panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 {
@@ -61,8 +50,8 @@ 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) &&
+		    drm_gem_shmem_purge(&shmem->base)) {
 			freed += shmem->base.size >> PAGE_SHIFT;
 			list_del_init(&shmem->madv_list);
 		}
-- 
2.20.1

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