Am 22.05.23 um 11:50 schrieb Matthew Auld:
On 22/05/2023 10:43, Thomas Zimmermann wrote:Hi Am 19.05.23 um 11:07 schrieb Matthew Auld: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>Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx> Shall I add the patch to drm-misc-fixes?Yes, please do. Thanks.
Merged. Thanks for the patch.
Best regards Thomas--- drivers/gpu/drm/drm_managed.c | 22 ++-------------------- include/drm/drm_managed.h | 18 +++++++++++++++++- 2 files changed, 19 insertions(+), 21 deletions(-)diff --git a/drivers/gpu/drm/drm_managed.c b/drivers/gpu/drm/drm_managed.cindex 4cf214de50c4..c21c3f623033 100644 --- 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, void *data)} 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); 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
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)
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