This is a note to let you know that I've just added the patch titled
drm/panfrost: Fix a deadlock between the shrinker and madvise path
to the 5.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-panfrost-fix-a-deadlock-between-the-shrinker-and-madvise-path.patch
and it can be found in the queue-5.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7d2d6d01293e6d9b42a6cb410be4158571f7fe9d Mon Sep 17 00:00:00 2001
From: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Date: Sun, 1 Nov 2020 18:40:16 +0100
Subject: drm/panfrost: Fix a deadlock between the shrinker and madvise path
From: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
commit 7d2d6d01293e6d9b42a6cb410be4158571f7fe9d upstream.
panfrost_ioctl_madvise() and panfrost_gem_purge() acquire the mappings
and shmem locks in different orders, thus leading to a potential
the mappings lock first.
Fixes: bdefca2d8dc0 ("drm/panfrost: Add the panfrost_gem_mapping concept")
Cc: <stable@xxxxxxxxxxxxxxx>
Cc: Christian Hewitt <christianshewitt@xxxxxxxxx>
Reported-by: Christian Hewitt <christianshewitt@xxxxxxxxx>
Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Reviewed-by: Steven Price <steven.price@xxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20201101174016.839110-1-boris.brezillon@xxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/panfrost/panfrost_gem.c | 4 +---
drivers/gpu/drm/panfrost/panfrost_gem.h | 2 +-
drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c | 14 +++++++++++---
3 files changed, 13 insertions(+), 7 deletions(-)
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -105,14 +105,12 @@ void panfrost_gem_mapping_put(struct pan
kref_put(&mapping->refcount, panfrost_gem_mapping_release);
}
-void panfrost_gem_teardown_mappings(struct panfrost_gem_object *bo)
+void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo)
{
struct panfrost_gem_mapping *mapping;
- mutex_lock(&bo->mappings.lock);
list_for_each_entry(mapping, &bo->mappings.list, node)
panfrost_gem_teardown_mapping(mapping);
- mutex_unlock(&bo->mappings.lock);
}
int panfrost_gem_open(struct drm_gem_object *obj, struct drm_file *file_priv)
--- a/drivers/gpu/drm/panfrost/panfrost_gem.h
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
@@ -82,7 +82,7 @@ struct panfrost_gem_mapping *
panfrost_gem_mapping_get(struct panfrost_gem_object *bo,
struct panfrost_file_priv *priv);
void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping);
-void panfrost_gem_teardown_mappings(struct panfrost_gem_object *bo);
+void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo);
void panfrost_gem_shrinker_init(struct drm_device *dev);
void panfrost_gem_shrinker_cleanup(struct drm_device *dev);
--- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
@@ -40,18 +40,26 @@ static bool panfrost_gem_purge(struct dr
{
struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
struct panfrost_gem_object *bo = to_panfrost_bo(obj);
+ bool ret = false;
if (atomic_read(&bo->gpu_usecount))
return false;
- if (!mutex_trylock(&shmem->pages_lock))
+ if (!mutex_trylock(&bo->mappings.lock))
return false;
- panfrost_gem_teardown_mappings(bo);
+ if (!mutex_trylock(&shmem->pages_lock))
+ goto unlock_mappings;
+
+ panfrost_gem_teardown_mappings_locked(bo);
drm_gem_shmem_purge_locked(obj);
+ ret = true;
mutex_unlock(&shmem->pages_lock);
- return true;
+
+unlock_mappings:
+ mutex_unlock(&bo->mappings.lock);
+ return ret;
}
static unsigned long
Patches currently in stable-queue which might be from boris.brezillon@xxxxxxxxxxxxx are
queue-5.9/drm-panfrost-fix-a-deadlock-between-the-shrinker-and-madvise-path.patch
