mutex

Linux 6.18.37 LTS: kernel/locking/mutex.c
Linux 6.18.37 LTS: include/linux/mutex.h
Linux 6.18.37 LTS: kernel/locking/rtmutex.c

/*
 * Lock a mutex (possibly interruptible), slowpath:
 */
static __always_inline int __sched
__mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclass,
		    struct lockdep_map *nest_lock, unsigned long ip,
		    struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
{
	struct mutex_waiter waiter;
	struct ww_mutex *ww;
	int ret;

	if (!use_ww_ctx)
		ww_ctx = NULL;

	might_sleep();

	MUTEX_WARN_ON(lock->magic != lock);

	ww = container_of(lock, struct ww_mutex, base);
	if (ww_ctx) {
		if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
			return -EALREADY;

		/*
		 * Reset the wounded flag after a kill. No other process can
		 * race and wound us here since they can't have a valid owner
		 * pointer if we don't have any locks held.
		 */
		if (ww_ctx->acquired == 0)
			ww_ctx->wounded = 0;

#ifdef CONFIG_DEBUG_LOCK_ALLOC
		nest_lock = &ww_ctx->dep_map;
#endif
	}

	preempt_disable();
	mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);

		return true;

	return false;
}

static __always_inline bool __mutex_unlock_fast(struct mutex *lock)
{
	unsigned long curr = (unsigned long)current;

	return atomic_long_try_cmpxchg_release(&lock->owner, &curr, 0UL);
}
#endif

static inline void __mutex_set_flag(struct mutex *lock, unsigned long flag)
{
	atomic_long_or(flag, &lock->owner);
}

static inline void __mutex_clear_flag(struct mutex *lock, unsigned long flag)
{
	atomic_long_andnot(flag, &lock->owner);
}

static inline bool __mutex_waiter_is_first(struct mutex *lock, struct mutex_waiter *waiter)
{
	return list_first_entry(&lock->wait_list, struct mutex_waiter, list) == waiter;
}

/*
 * Add @waiter to a given location in the lock wait_list and set the
 * FLAG_WAITERS flag if it's the first waiter.
 */
static void
__mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
		   struct list_head *list)
{
	debug_mutex_add_waiter(lock, waiter, current);

	list_add_tail(&waiter->list, list);
	if (__mutex_waiter_is_first(lock, waiter))