1 // SPDX-License-Identifier: GPL-2.0
74 	if ((atomic_read(&lock->state) & mask) != mask)  in six_set_bitmask()
75 		atomic_or(mask, &lock->state);  in six_set_bitmask()
80 	if (atomic_read(&lock->state) & mask)  in six_clear_bitmask()
81 		atomic_and(~mask, &lock->state);  in six_clear_bitmask()
91 		EBUG_ON(lock->owner);  in six_set_owner()
92 		lock->owner = owner;  in six_set_owner()
94 		EBUG_ON(lock->owner != current);  in six_set_owner()
104 		read_count += *per_cpu_ptr(lock->readers, cpu);  in pcpu_read_count()
109  * __do_six_trylock() - main trylock routine
111  * Returns 1 on success, 0 on failure
115  * wakeup: when a wakeup is required, we return -1 - wakeup_type.
123 	EBUG_ON(type == SIX_LOCK_write && lock->owner != task);  in __do_six_trylock()
125 		(try != !(atomic_read(&lock->state) & SIX_LOCK_HELD_write)));  in __do_six_trylock()
154 	if (type == SIX_LOCK_read && lock->readers) {  in __do_six_trylock()
156 		this_cpu_inc(*lock->readers); /* signal that we own lock */  in __do_six_trylock()
160 		old = atomic_read(&lock->state);  in __do_six_trylock()
163 		this_cpu_sub(*lock->readers, !ret);  in __do_six_trylock()
168 			if (atomic_read(&lock->state) & SIX_LOCK_WAITING_write)  in __do_six_trylock()
169 				ret = -1 - SIX_LOCK_write;  in __do_six_trylock()
171 	} else if (type == SIX_LOCK_write && lock->readers) {  in __do_six_trylock()
173 			atomic_add(SIX_LOCK_HELD_write, &lock->state);  in __do_six_trylock()
179 		 * Paired with the smp_mb() in read lock fast path (per-cpu mode)  in __do_six_trylock()
180 		 * and the one before atomic_read in read unlock path.  in __do_six_trylock()
186 			old = atomic_sub_return(SIX_LOCK_HELD_write, &lock->state);  in __do_six_trylock()
188 				ret = -1 - SIX_LOCK_read;  in __do_six_trylock()
191 		old = atomic_read(&lock->state);  in __do_six_trylock()
198 		} while (!atomic_try_cmpxchg_acquire(&lock->state, &old, old + l[type].lock_val));  in __do_six_trylock()
200 		EBUG_ON(ret && !(atomic_read(&lock->state) & l[type].held_mask));  in __do_six_trylock()
207 		(atomic_read(&lock->state) & SIX_LOCK_HELD_write));  in __do_six_trylock()
221 	raw_spin_lock(&lock->wait_lock);  in __six_lock_wakeup()
223 	list_for_each_entry_safe(w, next, &lock->wait_list, list) {  in __six_lock_wakeup()
224 		if (w->lock_want != lock_type)  in __six_lock_wakeup()
231 		ret = __do_six_trylock(lock, lock_type, w->task, false);  in __six_lock_wakeup()
237 		 * against the wakee noticing w->lock_acquired, returning, and  in __six_lock_wakeup()
240 		task = get_task_struct(w->task);  in __six_lock_wakeup()
241 		__list_del(w->list.prev, w->list.next);  in __six_lock_wakeup()
244 		 * __list_del before setting w->lock_acquired; @w is on the  in __six_lock_wakeup()
246 		 * after it sees w->lock_acquired with no other locking:  in __six_lock_wakeup()
249 		smp_store_release(&w->lock_acquired, true);  in __six_lock_wakeup()
256 	raw_spin_unlock(&lock->wait_lock);  in __six_lock_wakeup()
259 		lock_type = -ret - 1;  in __six_lock_wakeup()
284 		__six_lock_wakeup(lock, -ret - 1);  in do_six_trylock()
290  * six_trylock_ip - attempt to take a six lock without blocking
295  * Return: true on success, false on failure.
303 		six_acquire(&lock->dep_map, 1, type == SIX_LOCK_read, ip);  in six_trylock_ip()
309  * six_relock_ip - attempt to re-take a lock that was held previously
316  * Return: true on success, false on failure.
340 	 * that will live-lock because we won't let the owner complete.  in six_owner_running()
343 	struct task_struct *owner = READ_ONCE(lock->owner);  in six_owner_running()
351 				       struct six_lock_waiter *wait,  in six_optimistic_spin()  argument
360 	if (lock->wait_list.next != &wait->list)  in six_optimistic_spin()
363 	if (atomic_read(&lock->state) & SIX_LOCK_NOSPIN)  in six_optimistic_spin()
372 		 * wait->lock_acquired: pairs with the smp_store_release in  in six_optimistic_spin()
375 		if (smp_load_acquire(&wait->lock_acquired)) {  in six_optimistic_spin()
387 		 * everything in this loop to be re-loaded. We don't need  in six_optimistic_spin()
401 				       struct six_lock_waiter *wait,  in six_optimistic_spin()  argument
411 			     struct six_lock_waiter *wait,  in six_lock_slowpath()  argument
418 		EBUG_ON(atomic_read(&lock->state) & SIX_LOCK_HELD_write);  in six_lock_slowpath()
419 		atomic_add(SIX_LOCK_HELD_write, &lock->state);  in six_lock_slowpath()
424 	lock_contended(&lock->dep_map, ip);  in six_lock_slowpath()
426 	wait->task		= current;  in six_lock_slowpath()
427 	wait->lock_want		= type;  in six_lock_slowpath()
428 	wait->lock_acquired	= false;  in six_lock_slowpath()
430 	raw_spin_lock(&lock->wait_lock);  in six_lock_slowpath()
438 		wait->start_time = local_clock();  in six_lock_slowpath()
440 		if (!list_empty(&lock->wait_list)) {  in six_lock_slowpath()
442 				list_last_entry(&lock->wait_list,  in six_lock_slowpath()
445 			if (time_before_eq64(wait->start_time, last->start_time))  in six_lock_slowpath()
446 				wait->start_time = last->start_time + 1;  in six_lock_slowpath()
449 		list_add_tail(&wait->list, &lock->wait_list);  in six_lock_slowpath()
451 	raw_spin_unlock(&lock->wait_lock);  in six_lock_slowpath()
459 		__six_lock_wakeup(lock, -ret - 1);  in six_lock_slowpath()
463 	if (six_optimistic_spin(lock, wait, type))  in six_lock_slowpath()
471 		 * wait->lock_acquired: pairs with the smp_store_release in  in six_lock_slowpath()
474 		if (smp_load_acquire(&wait->lock_acquired))  in six_lock_slowpath()
484 			 * acquired the lock - should_sleep_fn() might have  in six_lock_slowpath()
488 			raw_spin_lock(&lock->wait_lock);  in six_lock_slowpath()
489 			acquired = wait->lock_acquired;  in six_lock_slowpath()
491 				list_del(&wait->list);  in six_lock_slowpath()
492 			raw_spin_unlock(&lock->wait_lock);  in six_lock_slowpath()
506 		six_lock_wakeup(lock, atomic_read(&lock->state), SIX_LOCK_read);  in six_lock_slowpath()
514  * six_lock_ip_waiter - take a lock, with full waitlist interface
517  * @wait:	pointer to wait object, which will be added to lock's waitlist
527  * @wait object should be embedded into the struct that tracks held locks -
528  * which must also be accessible in a thread-safe way.
533  * When this function must block, @wait will be added to @lock's waitlist before
534  * calling trylock, and before calling @should_sleep_fn, and @wait will not be
538  * @wait.start_time will be monotonically increasing for any given waitlist, and
541  * Return: 0 on success, or the return code from @should_sleep_fn on failure.
544 		       struct six_lock_waiter *wait,  in six_lock_ip_waiter()  argument
550 	wait->start_time = 0;  in six_lock_ip_waiter()
553 		six_acquire(&lock->dep_map, 0, type == SIX_LOCK_read, ip);  in six_lock_ip_waiter()
556 		: six_lock_slowpath(lock, type, wait, should_sleep_fn, p, ip);  in six_lock_ip_waiter()
559 		six_release(&lock->dep_map, ip);  in six_lock_ip_waiter()
561 		lock_acquired(&lock->dep_map, ip);  in six_lock_ip_waiter()
573 		lock->owner = NULL;  in do_six_unlock_type()
576 	    lock->readers) {  in do_six_unlock_type()
578 		this_cpu_dec(*lock->readers);  in do_six_unlock_type()
580 		state = atomic_read(&lock->state);  in do_six_unlock_type()
585 			v += atomic_read(&lock->state) & SIX_LOCK_NOSPIN;  in do_six_unlock_type()
587 		EBUG_ON(!(atomic_read(&lock->state) & l[type].held_mask));  in do_six_unlock_type()
588 		state = atomic_sub_return_release(v, &lock->state);  in do_six_unlock_type()
595  * six_unlock_ip - drop a six lock
604  * six_lock_read(&foo->lock);				read count 1
605  * six_lock_increment(&foo->lock, SIX_LOCK_read);	read count 2
606  * six_lock_unlock(&foo->lock, SIX_LOCK_read);		read count 1
607  * six_lock_unlock(&foo->lock, SIX_LOCK_read);		read count 0
612 		!(atomic_read(&lock->state) & SIX_LOCK_HELD_intent));  in six_unlock_ip()
615 		lock->owner != current);  in six_unlock_ip()
618 		six_release(&lock->dep_map, ip);  in six_unlock_ip()
620 		lock->seq++;  in six_unlock_ip()
623 	    lock->intent_lock_recurse) {  in six_unlock_ip()
624 		--lock->intent_lock_recurse;  in six_unlock_ip()
633  * six_lock_downgrade - convert an intent lock to a read lock
636  * @lock will have read count incremented and intent count decremented
646  * six_lock_tryupgrade - attempt to convert read lock to an intent lock
649  * On success, @lock will have intent count incremented and read count
652  * Return: true on success, false on failure
656 	u32 old = atomic_read(&lock->state), new;  in six_lock_tryupgrade()
664 		if (!lock->readers) {  in six_lock_tryupgrade()
666 			new -= l[SIX_LOCK_read].lock_val;  in six_lock_tryupgrade()
670 	} while (!atomic_try_cmpxchg_acquire(&lock->state, &old, new));  in six_lock_tryupgrade()
672 	if (lock->readers)  in six_lock_tryupgrade()
673 		this_cpu_dec(*lock->readers);  in six_lock_tryupgrade()
682  * six_trylock_convert - attempt to convert a held lock from one type to another
687  * On success, @lock will have intent count incremented and read count
690  * Return: true on success, false on failure
711  * six_lock_increment - increase held lock count on a lock that is already held
723 	six_acquire(&lock->dep_map, 0, type == SIX_LOCK_read, _RET_IP_);  in six_lock_increment()
729 		if (lock->readers) {  in six_lock_increment()
730 			this_cpu_inc(*lock->readers);  in six_lock_increment()
732 			EBUG_ON(!(atomic_read(&lock->state) &  in six_lock_increment()
735 			atomic_add(l[type].lock_val, &lock->state);  in six_lock_increment()
739 		EBUG_ON(!(atomic_read(&lock->state) & SIX_LOCK_HELD_intent));  in six_lock_increment()
740 		lock->intent_lock_recurse++;  in six_lock_increment()
750  * six_lock_wakeup_all - wake up all waiters on @lock
753  * Wakeing up waiters will cause them to re-run should_sleep_fn, which may then
756  * This function is never needed in a bug-free program; it's only useful in
761 	u32 state = atomic_read(&lock->state);  in six_lock_wakeup_all()
768 	raw_spin_lock(&lock->wait_lock);  in six_lock_wakeup_all()
769 	list_for_each_entry(w, &lock->wait_list, list)  in six_lock_wakeup_all()
770 		wake_up_process(w->task);  in six_lock_wakeup_all()
771 	raw_spin_unlock(&lock->wait_lock);  in six_lock_wakeup_all()
776  * six_lock_counts - return held lock counts, for each lock type
779  * Return: the number of times a lock is held for read, intent and write.
785 	ret.n[SIX_LOCK_read]	= !lock->readers  in six_lock_counts()
786 		? atomic_read(&lock->state) & SIX_LOCK_HELD_read  in six_lock_counts()
788 	ret.n[SIX_LOCK_intent]	= !!(atomic_read(&lock->state) & SIX_LOCK_HELD_intent) +  in six_lock_counts()
789 		lock->intent_lock_recurse;  in six_lock_counts()
790 	ret.n[SIX_LOCK_write]	= !!(atomic_read(&lock->state) & SIX_LOCK_HELD_write);  in six_lock_counts()
797  * six_lock_readers_add - directly manipulate reader count of a lock
801  * When an upper layer is implementing lock reentrency, we may have both read
802  * and intent locks on the same lock.
804  * When we need to take a write lock, the read locks will cause self-deadlock,
805  * because six locks themselves do not track which read locks are held by the
806  * current thread and which are held by a different thread - it does no
807  * per-thread tracking of held locks.
810  * failed, count up its own read locks, subtract them, take the write lock, and
811  * then re-add them.
818 	if (lock->readers) {  in six_lock_readers_add()
819 		this_cpu_add(*lock->readers, nr);  in six_lock_readers_add()
821 		EBUG_ON((int) (atomic_read(&lock->state) & SIX_LOCK_HELD_read) + nr < 0);  in six_lock_readers_add()
823 		atomic_add(nr, &lock->state);  in six_lock_readers_add()
829  * six_lock_exit - release resources held by a lock prior to freeing
833  * required to free the percpu read counts.
837 	WARN_ON(lock->readers && pcpu_read_count(lock));  in six_lock_exit()
838 	WARN_ON(atomic_read(&lock->state) & SIX_LOCK_HELD_read);  in six_lock_exit()
840 	free_percpu(lock->readers);  in six_lock_exit()
841 	lock->readers = NULL;  in six_lock_exit()
848 	atomic_set(&lock->state, 0);  in __six_lock_init()
849 	raw_spin_lock_init(&lock->wait_lock);  in __six_lock_init()
850 	INIT_LIST_HEAD(&lock->wait_list);  in __six_lock_init()
853 	lockdep_init_map(&lock->dep_map, name, key, 0);  in __six_lock_init()
863 		 * We don't return an error here on memory allocation failure  in __six_lock_init()
865 		 * same semantics in non-percpu mode: callers can check for  in __six_lock_init()
866 		 * failure if they wish by checking lock->readers, but generally  in __six_lock_init()
869 		lock->readers = alloc_percpu(unsigned);  in __six_lock_init()