The following commit has been merged into the locking/core branch of tip: Commit-ID: 64b7b715f7f92ae3233446b4a4cdda3524fcd4b0 Gitweb: https://git.kernel.org/tip/64b7b715f7f92ae3233446b4a4cdda3524fcd4b0 Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Sun, 15 Aug 2021 23:29:12 +02:00 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitterDate: Tue, 17 Aug 2021 19:05:49 +02:00 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: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Link: https://lore.kernel.org/r/20210815211305.468835790@xxxxxxxxxxxxx --- kernel/futex.c | 90 ++++++++++++++++++++++--------------------------- 1 file changed, 41 insertions(+), 49 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index 5439742..6cb6b5d 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2104,20 +2104,17 @@ retry_private: 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) { - mark_wake_futex(&wake_q, this); + /* 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 @@ retry_private: /* * Requeue nr_requeue waiters and possibly one more in the case * of requeue_pi if we couldn't acquire the lock atomically. + * + * 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. */ - if (requeue_pi) { + 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); + if (ret == 1) { /* - * 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. + * 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. */ - 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); - 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. - */ - requeue_pi_wake_futex(this, &key2, hb2); - 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. - */ - 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. - */ - break; - } + 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. + */ + this->pi_state = NULL; + put_pi_state(pi_state); + /* + * 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++; } /*
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