Commit 2d9200cf authored by Kent Overstreet's avatar Kent Overstreet
Browse files

six locks: Use atomic_try_cmpxchg_acquire() 



This switches to a newer cmpxchg variant which updates @old for us on
failure, simplifying the cmpxchg loops a bit and supposedly generating
better code.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent c4687a4a

fs/bcachefs/six.c

+6 −11
Original line number Diff line number Diff line
@@ -116,7 +116,7 @@ static int __do_six_trylock(struct six_lock *lock, enum six_lock_type type, 
			    struct task_struct *task, bool try)

{

	int ret;

	u32 old, new, v;

	u32 old;



	EBUG_ON(type == SIX_LOCK_write && lock->owner != task);

	EBUG_ON(type == SIX_LOCK_write &&
@@ -177,19 +177,14 @@ static int __do_six_trylock(struct six_lock *lock, enum six_lock_type type, 
				ret = -1 - SIX_LOCK_read;

		}

	} else {

		v = atomic_read(&lock->state);

		old = atomic_read(&lock->state);

		do {

			new = old = v;



			ret = !(old & l[type].lock_fail);



			if (!ret || (type == SIX_LOCK_write && !try)) {

				smp_mb();

				break;

			}



			new += l[type].lock_val;

		} while ((v = atomic_cmpxchg_acquire(&lock->state, old, new)) != old);

		} while (!atomic_try_cmpxchg_acquire(&lock->state, &old, old + l[type].lock_val));



		EBUG_ON(ret && !(atomic_read(&lock->state) & l[type].held_mask));

	}
@@ -675,10 +670,10 @@ EXPORT_SYMBOL_GPL(six_lock_downgrade); 
 */

bool six_lock_tryupgrade(struct six_lock *lock)

{

	u32 old, new, v = atomic_read(&lock->state);

	u32 old = atomic_read(&lock->state), new;



	do {

		new = old = v;

		new = old;



		if (new & SIX_LOCK_HELD_intent)

			return false;
@@ -689,7 +684,7 @@ bool six_lock_tryupgrade(struct six_lock *lock) 
		}



		new |= SIX_LOCK_HELD_intent;

	} while ((v = atomic_cmpxchg_acquire(&lock->state, old, new)) != old);

	} while (!atomic_try_cmpxchg_acquire(&lock->state, &old, new));



	if (lock->readers)

		this_cpu_dec(*lock->readers);