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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>,
	Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
	Robin Murphy <robin.murphy@arm.com>
Subject: [PATCH v2 6/8] drm/panfrost: Use mutex_trylock in panfrost_gem_purge
Date: Thu, 22 Aug 2019 21:12:14 -0500	[thread overview]
Message-ID: <20190823021216.5862-7-robh@kernel.org> (raw)
In-Reply-To: <20190823021216.5862-1-robh@kernel.org>

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: Steven Price <steven.price@arm.com>
Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Rob Herring <robh@kernel.org>
---
v2: new patch

 drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
index d191632b6197..458f0fa68111 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
@@ -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);
 		}
-- 
2.20.1

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  parent reply	other threads:[~2019-08-23  2:12 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-23  2:12 (unknown) Rob Herring
2019-08-23  2:12 ` [PATCH v2 1/8] drm/panfrost: Fix possible suspend in panfrost_remove Rob Herring
2019-08-23 14:50   ` Steven Price
2019-08-23  2:12 ` [PATCH v2 2/8] drm/panfrost: Rework runtime PM initialization Rob Herring
2019-08-23 10:54   ` Robin Murphy
2019-08-23 12:16     ` Rob Herring
2019-08-23  2:12 ` [PATCH v2 3/8] drm/panfrost: Hold runtime PM reference until jobs complete Rob Herring
2019-08-23 14:50   ` Steven Price
2019-08-23 15:13     ` Rob Herring
2019-08-23  2:12 ` [PATCH v2 4/8] drm/shmem: Do dma_unmap_sg before purging pages Rob Herring
2019-08-23  2:12 ` [PATCH v2 5/8] drm/shmem: Use mutex_trylock in drm_gem_shmem_purge Rob Herring
2019-08-23 14:53   ` Steven Price
2019-08-23  2:12 ` Rob Herring [this message]
2019-08-23 14:55   ` [PATCH v2 6/8] drm/panfrost: Use mutex_trylock in panfrost_gem_purge Steven Price
2019-08-23  2:12 ` [PATCH v2 7/8] drm/panfrost: Rework page table flushing and runtime PM interaction Rob Herring
2019-08-23 11:11   ` Robin Murphy
2019-08-23 15:05     ` Steven Price
2019-08-23 15:44       ` Robin Murphy
2019-08-23 15:57         ` Rob Herring
2019-08-23 16:16           ` Robin Murphy
2019-08-23 16:45             ` Rob Herring
2019-08-23 15:09   ` Steven Price
2019-08-23 15:49     ` Rob Herring
2019-08-23  2:12 ` [PATCH v2 8/8] drm/panfrost: Remove unnecessary flushing from tlb_inv_context Rob Herring
2019-08-23 12:56   ` Robin Murphy
2019-08-23 13:18     ` Rob Herring
2019-08-23 14:05       ` Robin Murphy
2019-08-23 14:26         ` Rob Herring
2019-08-23 14:56           ` Robin Murphy
2019-08-23 15:12   ` Steven Price

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