From 47907461e4f6fcdce8cf91dd164369192deeb7c4 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Fri, 19 Dec 2025 16:40:09 +0100 Subject: locking/ww_mutex: Support Clang's context analysis Add support for Clang's context analysis for ww_mutex. The programming model for ww_mutex is subtly more complex than other locking primitives when using ww_acquire_ctx. Encoding the respective pre-conditions for ww_mutex lock/unlock based on ww_acquire_ctx state using Clang's context analysis makes incorrect use of the API harder. Signed-off-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20251219154418.3592607-21-elver@google.com --- include/linux/ww_mutex.h | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) (limited to 'include') diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h index 45ff6f7a872b..58e959ee10e9 100644 --- a/include/linux/ww_mutex.h +++ b/include/linux/ww_mutex.h @@ -44,7 +44,7 @@ struct ww_class { unsigned int is_wait_die; }; -struct ww_mutex { +context_lock_struct(ww_mutex) { struct WW_MUTEX_BASE base; struct ww_acquire_ctx *ctx; #ifdef DEBUG_WW_MUTEXES @@ -52,7 +52,7 @@ struct ww_mutex { #endif }; -struct ww_acquire_ctx { +context_lock_struct(ww_acquire_ctx) { struct task_struct *task; unsigned long stamp; unsigned int acquired; @@ -107,6 +107,7 @@ struct ww_acquire_ctx { */ static inline void ww_mutex_init(struct ww_mutex *lock, struct ww_class *ww_class) + __assumes_ctx_lock(lock) { ww_mutex_base_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key); lock->ctx = NULL; @@ -141,6 +142,7 @@ static inline void ww_mutex_init(struct ww_mutex *lock, */ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, struct ww_class *ww_class) + __acquires(ctx) __no_context_analysis { ctx->task = current; ctx->stamp = atomic_long_inc_return_relaxed(&ww_class->stamp); @@ -179,6 +181,7 @@ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, * data structures. */ static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) + __releases(ctx) __acquires_shared(ctx) __no_context_analysis { #ifdef DEBUG_WW_MUTEXES lockdep_assert_held(ctx); @@ -196,6 +199,7 @@ static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) * mutexes have been released with ww_mutex_unlock. */ static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) + __releases_shared(ctx) __no_context_analysis { #ifdef CONFIG_DEBUG_LOCK_ALLOC mutex_release(&ctx->first_lock_dep_map, _THIS_IP_); @@ -245,7 +249,8 @@ static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) * * A mutex acquired with this function must be released with ww_mutex_unlock. */ -extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx); +extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) + __cond_acquires(0, lock) __must_hold(ctx); /** * ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible @@ -278,7 +283,8 @@ extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acq * A mutex acquired with this function must be released with ww_mutex_unlock. */ extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, - struct ww_acquire_ctx *ctx); + struct ww_acquire_ctx *ctx) + __cond_acquires(0, lock) __must_hold(ctx); /** * ww_mutex_lock_slow - slowpath acquiring of the w/w mutex @@ -305,6 +311,7 @@ extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock, */ static inline void ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) + __acquires(lock) __must_hold(ctx) __no_context_analysis { int ret; #ifdef DEBUG_WW_MUTEXES @@ -342,6 +349,7 @@ ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) static inline int __must_check ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) + __cond_acquires(0, lock) __must_hold(ctx) { #ifdef DEBUG_WW_MUTEXES DEBUG_LOCKS_WARN_ON(!ctx->contending_lock); @@ -349,10 +357,11 @@ ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, return ww_mutex_lock_interruptible(lock, ctx); } -extern void ww_mutex_unlock(struct ww_mutex *lock); +extern void ww_mutex_unlock(struct ww_mutex *lock) __releases(lock); extern int __must_check ww_mutex_trylock(struct ww_mutex *lock, - struct ww_acquire_ctx *ctx); + struct ww_acquire_ctx *ctx) + __cond_acquires(true, lock) __must_hold(ctx); /*** * ww_mutex_destroy - mark a w/w mutex unusable @@ -363,6 +372,7 @@ extern int __must_check ww_mutex_trylock(struct ww_mutex *lock, * this function is called. */ static inline void ww_mutex_destroy(struct ww_mutex *lock) + __must_not_hold(lock) { #ifndef CONFIG_PREEMPT_RT mutex_destroy(&lock->base); -- cgit v1.2.3