Matthew Auld c21f11d182 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: e13f13e039 ("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		2023-05-22 12:23:50 +02:00
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drm	drm: fix drmm_mutex_init()	2023-05-22 12:23:50 +02:00
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