This is a note to let you know that I've just added the patch titled
drm: fix drmm_mutex_init()
to the 6.1-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-fix-drmm_mutex_init.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c21f11d182c2180d8b90eaff84f574cfa845b250 Mon Sep 17 00:00:00 2001
From: Matthew Auld <matthew.auld@xxxxxxxxx>
Date: Fri, 19 May 2023 10:07:33 +0100
Subject: drm: fix drmm_mutex_init()
MIME-Version: 1.0
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From: Matthew Auld <matthew.auld@xxxxxxxxx>
commit c21f11d182c2180d8b90eaff84f574cfa845b250 upstream.
In mutex_init() lockdep identifies a lock by defining a special static
key for each lock class. However if we wrap the macro in a function,
like in drmm_mutex_init(), we end up generating:
int drmm_mutex_init(struct drm_device *dev, struct mutex *lock)
{
static struct lock_class_key __key;
__mutex_init((lock), "lock", &__key);
....
}
The static __key here is what lockdep uses to identify the lock class,
however since this is just a normal function the key here will be
created once, where all callers then use the same key. In effect the
mutex->depmap.key will be the same pointer for different
drmm_mutex_init() callers. This then results in impossible lockdep
splats since lockdep thinks completely unrelated locks are the same lock
class.
To fix this turn drmm_mutex_init() into a macro such that it generates a
different "static struct lock_class_key __key" for each invocation,
which looks to be inline with what mutex_init() wants.
v2:
- Revamp the commit message with clearer explanation of the issue.
- Rather export __drmm_mutex_release() than static inline.
Reported-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Reported-by: Sarah Walker <sarah.walker@xxxxxxxxxx>
Fixes: e13f13e039dc ("drm: Add DRM-managed mutex_init()")
Cc: Stanislaw Gruszka <stanislaw.gruszka@xxxxxxxxxxxxxxx>
Cc: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@xxxxxxxxxxxxxxx>
Reviewed-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20230519090733.489019-1-matthew.auld@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_managed.c | 22 ++--------------------
include/drm/drm_managed.h | 18 +++++++++++++++++-
2 files changed, 19 insertions(+), 21 deletions(-)
--- a/drivers/gpu/drm/drm_managed.c
+++ b/drivers/gpu/drm/drm_managed.c
@@ -264,28 +264,10 @@ void drmm_kfree(struct drm_device *dev,
}
EXPORT_SYMBOL(drmm_kfree);
-static void drmm_mutex_release(struct drm_device *dev, void *res)
+void __drmm_mutex_release(struct drm_device *dev, void *res)
{
struct mutex *lock = res;
mutex_destroy(lock);
}
-
-/**
- * drmm_mutex_init - &drm_device-managed mutex_init()
- * @dev: DRM device
- * @lock: lock to be initialized
- *
- * Returns:
- * 0 on success, or a negative errno code otherwise.
- *
- * This is a &drm_device-managed version of mutex_init(). The initialized
- * lock is automatically destroyed on the final drm_dev_put().
- */
-int drmm_mutex_init(struct drm_device *dev, struct mutex *lock)
-{
- mutex_init(lock);
-
- return drmm_add_action_or_reset(dev, drmm_mutex_release, lock);
-}
-EXPORT_SYMBOL(drmm_mutex_init);
+EXPORT_SYMBOL(__drmm_mutex_release);
--- a/include/drm/drm_managed.h
+++ b/include/drm/drm_managed.h
@@ -105,6 +105,22 @@ char *drmm_kstrdup(struct drm_device *de
void drmm_kfree(struct drm_device *dev, void *data);
-int drmm_mutex_init(struct drm_device *dev, struct mutex *lock);
+void __drmm_mutex_release(struct drm_device *dev, void *res);
+
+/**
+ * drmm_mutex_init - &drm_device-managed mutex_init()
+ * @dev: DRM device
+ * @lock: lock to be initialized
+ *
+ * Returns:
+ * 0 on success, or a negative errno code otherwise.
+ *
+ * This is a &drm_device-managed version of mutex_init(). The initialized
+ * lock is automatically destroyed on the final drm_dev_put().
+ */
+#define drmm_mutex_init(dev, lock) ({ \
+ mutex_init(lock); \
+ drmm_add_action_or_reset(dev, __drmm_mutex_release, lock); \
+}) \
#endif
Patches currently in stable-queue which might be from matthew.auld@xxxxxxxxx are
queue-6.1/drm-fix-drmm_mutex_init.patch
