Commit 64b7b715 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

futex: Restructure futex_requeue() 



No point in taking two more 'requeue_pi' conditionals just to get to the
requeue. Same for the requeue_pi case just the other way round.

No functional change.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211305.468835790@linutronix.de
parent 59c7ecf1

kernel/futex.c

+41 −49
Original line number Diff line number Diff line
@@ -2104,20 +2104,17 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags, 
			break;

		}



		/*

		 * Wake nr_wake waiters.  For requeue_pi, if we acquired the

		 * lock, we already woke the top_waiter.  If not, it will be

		 * woken by futex_unlock_pi().

		 */

		if (++task_count <= nr_wake && !requeue_pi) {

		/* Plain futexes just wake or requeue and are done */

		if (!requeue_pi) {

			if (++task_count <= nr_wake)

				mark_wake_futex(&wake_q, this);

			else

				requeue_futex(this, hb1, hb2, &key2);

			continue;

		}



		/* Ensure we requeue to the expected futex for requeue_pi. */

		if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) {

			/* Don't account for it */

			task_count--;

		if (!match_futex(this->requeue_pi_key, &key2)) {

			ret = -EINVAL;

			break;

		}
@@ -2125,50 +2122,45 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags, 
		/*

		 * Requeue nr_requeue waiters and possibly one more in the case

		 * of requeue_pi if we couldn't acquire the lock atomically.

		 */

		if (requeue_pi) {

			/*

			 * Prepare the waiter to take the rt_mutex. Take a

			 * refcount on the pi_state and store the pointer in

			 * the futex_q object of the waiter.

		 *

		 * Prepare the waiter to take the rt_mutex. Take a refcount

		 * on the pi_state and store the pointer in the futex_q

		 * object of the waiter.

		 */

		get_pi_state(pi_state);

		this->pi_state = pi_state;

		ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex,

							this->rt_waiter,

							this->task);

						this->rt_waiter, this->task);

		if (ret == 1) {

			/*

				 * We got the lock. We do neither drop the

				 * refcount on pi_state nor clear

				 * this->pi_state because the waiter needs the

				 * pi_state for cleaning up the user space

				 * value. It will drop the refcount after

				 * doing so.

			 * We got the lock. We do neither drop the refcount

			 * on pi_state nor clear this->pi_state because the

			 * waiter needs the pi_state for cleaning up the

			 * user space value. It will drop the refcount

			 * after doing so.

			 */

			requeue_pi_wake_futex(this, &key2, hb2);

			task_count++;

			continue;

		} else if (ret) {

			/*

				 * rt_mutex_start_proxy_lock() detected a

				 * potential deadlock when we tried to queue

				 * that waiter. Drop the pi_state reference

				 * which we took above and remove the pointer

				 * to the state from the waiters futex_q

				 * object.

			 * rt_mutex_start_proxy_lock() detected a potential

			 * deadlock when we tried to queue that waiter.

			 * Drop the pi_state reference which we took above

			 * and remove the pointer to the state from the

			 * waiters futex_q object.

			 */

			this->pi_state = NULL;

			put_pi_state(pi_state);

				/* Don't account for it */

				task_count--;

			/*

				 * We stop queueing more waiters and let user

				 * space deal with the mess.

			 * We stop queueing more waiters and let user space

			 * deal with the mess.

			 */

			break;

		}

		}

		/* Waiter is queued, move it to hb2 */

		requeue_futex(this, hb1, hb2, &key2);

		task_count++;

	}



	/*