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authorMatthew Auld <matthew.auld@intel.com>2023-05-19 12:07:33 +0300
committerThomas Zimmermann <tzimmermann@suse.de>2023-05-22 13:23:50 +0300
commitc21f11d182c2180d8b90eaff84f574cfa845b250 (patch)
tree2e2e2b2a4493becaa5c557d4ba7b15875acbbc1c /include/drm
parentaa8bf93101a185b49f83c9137453571a08be6e76 (diff)
downloadlinux-c21f11d182c2180d8b90eaff84f574cfa845b250.tar.xz
drm: fix drmm_mutex_init()
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@linux.intel.com> Reported-by: Sarah Walker <sarah.walker@imgtec.com> Fixes: e13f13e039dc ("drm: Add DRM-managed mutex_init()") Cc: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com> Cc: Boris Brezillon <boris.brezillon@collabora.com> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: Jocelyn Falempe <jfalempe@redhat.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: dri-devel@lists.freedesktop.org Signed-off-by: Matthew Auld <matthew.auld@intel.com> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com> Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com> Acked-by: Thomas Zimmermann <tzimmermann@suse.de> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Link: https://patchwork.freedesktop.org/patch/msgid/20230519090733.489019-1-matthew.auld@intel.com
Diffstat (limited to 'include/drm')
-rw-r--r--include/drm/drm_managed.h18
1 files changed, 17 insertions, 1 deletions
diff --git a/include/drm/drm_managed.h b/include/drm/drm_managed.h
index 359883942612..ad08f834af40 100644
--- a/include/drm/drm_managed.h
+++ b/include/drm/drm_managed.h
@@ -105,6 +105,22 @@ char *drmm_kstrdup(struct drm_device *dev, const char *s, gfp_t gfp);
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