From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Juri Lelli <juri.lelli@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>,
Boqun Feng <boqun.feng@gmail.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Davidlohr Bueso <dave@stgolabs.net>,
Mike Galbraith <efault@gmx.de>
Subject: [patch V4 60/68] futex: Restructure futex_requeue()
Date: Wed, 11 Aug 2021 14:23:44 +0200 (CEST) [thread overview]
Message-ID: <20210811121417.711347054@linutronix.de> (raw)
In-Reply-To: 20210811120348.855823694@linutronix.de
From: Thomas Gleixner <tglx@linutronix.de>
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@linutronix.de>
---
kernel/futex.c | 90 +++++++++++++++++++++++++--------------------------------
1 file changed, 41 insertions(+), 49 deletions(-)
---
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2104,20 +2104,17 @@ static int futex_requeue(u32 __user *uad
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 @@ static int futex_requeue(u32 __user *uad
/*
* 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) {
+ /*
+ * 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.
+ */
+ this->pi_state = NULL;
+ put_pi_state(pi_state);
/*
- * 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 stop queueing more waiters and let user space
+ * deal with the mess.
*/
- 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;
- }
+ break;
}
+ /* Waiter is queued, move it to hb2 */
requeue_futex(this, hb1, hb2, &key2);
+ task_count++;
}
/*
next prev parent reply other threads:[~2021-08-11 12:26 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-11 12:22 [patch V4 00/68] locking, sched: The PREEMPT-RT locking infrastructure Thomas Gleixner
2021-08-11 12:22 ` [patch V4 01/68] sched: Split out the wakeup state check Thomas Gleixner
2021-08-11 12:22 ` [patch V4 02/68] sched: Introduce TASK_RTLOCK_WAIT Thomas Gleixner
2021-08-11 12:22 ` [patch V4 03/68] sched: Reorganize current::__state helpers Thomas Gleixner
2021-08-11 12:22 ` [patch V4 04/68] sched: Prepare for RT sleeping spin/rwlocks Thomas Gleixner
2021-08-11 12:22 ` [patch V4 05/68] sched: Rework the __schedule() preempt argument Thomas Gleixner
2021-08-11 12:22 ` [patch V4 06/68] sched: Provide schedule point for RT locks Thomas Gleixner
2021-08-11 12:22 ` [patch V4 07/68] sched/wake_q: Provide WAKE_Q_HEAD_INITIALIZER Thomas Gleixner
2021-08-11 12:22 ` [patch V4 08/68] media/atomisp: Use lockdep instead of *mutex_is_locked() Thomas Gleixner
2021-08-11 12:22 ` [patch V4 09/68] rtmutex: Remove rt_mutex_is_locked() Thomas Gleixner
2021-08-11 12:22 ` [patch V4 10/68] rtmutex: Convert macros to inlines Thomas Gleixner
2021-08-11 12:22 ` [patch V4 11/68] rtmutex: Switch to try_cmpxchg() Thomas Gleixner
2021-08-11 12:22 ` [patch V4 12/68] rtmutex: Split API and implementation Thomas Gleixner
2021-08-11 12:22 ` [patch V4 13/68] rtmutex: Split out the inner parts of struct rtmutex Thomas Gleixner
2021-08-11 12:22 ` [patch V4 14/68] locking/rtmutex: Provide rt_mutex_slowlock_locked() Thomas Gleixner
2021-08-11 12:22 ` [patch V4 15/68] rtmutex: Provide rt_mutex_base_is_locked() Thomas Gleixner
2021-08-11 12:22 ` [patch V4 16/68] locking: Add base code for RT rw_semaphore and rwlock Thomas Gleixner
2021-08-11 12:22 ` [patch V4 17/68] locking/rwsem: Add rtmutex based R/W semaphore implementation Thomas Gleixner
2021-08-11 12:22 ` [patch V4 18/68] locking/rtmutex: Add wake_state to rt_mutex_waiter Thomas Gleixner
2021-08-11 12:22 ` [patch V4 19/68] locking/rtmutex: Provide rt_wake_q and helpers Thomas Gleixner
2021-08-11 12:22 ` [patch V4 20/68] locking/rtmutex: Use rt_mutex_wake_q_head Thomas Gleixner
2021-08-11 12:22 ` [patch V4 21/68] locking/rtmutex: Prepare RT rt_mutex_wake_q for RT locks Thomas Gleixner
2021-08-11 12:22 ` [patch V4 22/68] locking/rtmutex: Guard regular sleeping locks specific functions Thomas Gleixner
2021-08-11 12:22 ` [patch V4 23/68] locking/spinlock: Split the lock types header Thomas Gleixner
2021-08-11 12:23 ` [patch V4 24/68] locking/rtmutex: Prevent future include recursion hell Thomas Gleixner
2021-08-11 12:23 ` [patch V4 25/68] locking/lockdep: Reduce includes in debug_locks.h Thomas Gleixner
2021-08-11 12:23 ` [patch V4 26/68] rbtree: Split out the rbtree type definitions Thomas Gleixner
2021-08-11 12:23 ` [patch V4 27/68] locking/rtmutex: Include only rbtree types Thomas Gleixner
2021-08-11 12:23 ` [patch V4 28/68] locking/spinlock: Provide RT specific spinlock type Thomas Gleixner
2021-08-11 12:23 ` [patch V4 29/68] locking/spinlock: Provide RT variant header Thomas Gleixner
2021-08-11 12:23 ` [patch V4 30/68] locking/rtmutex: Provide the spin/rwlock core lock function Thomas Gleixner
2021-08-11 12:23 ` [patch V4 31/68] locking/spinlock: Provide RT variant Thomas Gleixner
2021-08-11 12:23 ` [patch V4 32/68] locking/rwlock: " Thomas Gleixner
2021-08-11 12:23 ` [patch V4 33/68] locking/rtmutex: Squash !RT tasks to DEFAULT_PRIO Thomas Gleixner
2021-08-11 12:23 ` [patch V4 34/68] locking/mutex: Consolidate core headers Thomas Gleixner
2021-08-11 12:23 ` [patch V4 35/68] locking/mutex: Move waiter to core header Thomas Gleixner
2021-08-11 12:23 ` [patch V4 36/68] locking/ww_mutex: Move ww_mutex declarations into ww_mutex.h Thomas Gleixner
2021-08-11 12:23 ` [patch V4 37/68] locking/mutex: Make mutex::wait_lock raw Thomas Gleixner
2021-08-11 12:23 ` [patch V4 38/68] locking/ww_mutex: Simplify lockdep annotation Thomas Gleixner
2021-08-11 12:23 ` [patch V4 39/68] locking/ww_mutex: Gather mutex_waiter initialization Thomas Gleixner
2021-08-11 12:23 ` [patch V4 40/68] locking/ww_mutex: Split up ww_mutex_unlock() Thomas Gleixner
2021-08-11 12:23 ` [patch V4 41/68] locking/ww_mutex: Split W/W implementation logic Thomas Gleixner
2021-08-11 12:23 ` [patch V4 42/68] locking/ww_mutex: Remove __sched annotation Thomas Gleixner
2021-08-11 12:23 ` [patch V4 43/68] locking/ww_mutex: Abstract waiter iteration Thomas Gleixner
2021-08-11 12:23 ` [patch V4 44/68] locking/ww_mutex: Abstract waiter enqueueing Thomas Gleixner
2021-08-11 12:23 ` [patch V4 45/68] locking/ww_mutex: Abstract mutex accessors Thomas Gleixner
2021-08-11 12:23 ` [patch V4 46/68] locking/ww_mutex: Abstract mutex types Thomas Gleixner
2021-08-11 12:23 ` [patch V4 47/68] locking/ww_mutex: Abstract internal lock access Thomas Gleixner
2021-08-11 12:23 ` [patch V4 48/68] locking/ww_mutex: Implement rt_mutex accessors Thomas Gleixner
2021-08-11 12:23 ` [patch V4 49/68] locking/ww_mutex: Add RT priority to W/W order Thomas Gleixner
2021-08-11 12:23 ` [patch V4 50/68] locking/ww_mutex: Add rt_mutex based lock type and accessors Thomas Gleixner
2021-08-11 12:23 ` [patch V4 51/68] locking/rtmutex: Extend the rtmutex core to support ww_mutex Thomas Gleixner
2021-08-11 12:23 ` [patch V4 52/68] locking/ww_mutex: Implement rtmutex based ww_mutex API functions Thomas Gleixner
2021-08-11 12:23 ` [patch V4 53/68] locking/rtmutex: Add mutex variant for RT Thomas Gleixner
2021-08-11 12:23 ` [patch V4 54/68] lib/test_lockup: Adapt to changed variables Thomas Gleixner
2021-08-11 12:23 ` [patch V4 55/68] futex: Validate waiter correctly in futex_proxy_trylock_atomic() Thomas Gleixner
2021-08-11 12:23 ` [patch V4 56/68] futex: Cleanup stale comments Thomas Gleixner
2021-08-11 12:23 ` [patch V4 57/68] futex: Clarify futex_requeue() PI handling Thomas Gleixner
2021-08-11 12:23 ` [patch V4 58/68] futex: Remove bogus condition for requeue PI Thomas Gleixner
2021-08-11 12:23 ` [patch V4 59/68] futex: Correct the number of requeued waiters for PI Thomas Gleixner
2021-08-11 12:23 ` Thomas Gleixner [this message]
2021-08-11 12:23 ` [patch V4 61/68] futex: Clarify comment in futex_requeue() Thomas Gleixner
2021-08-11 12:23 ` [patch V4 62/68] futex: Reorder sanity checks " Thomas Gleixner
2021-08-11 12:23 ` [patch V4 63/68] futex: Simplify handle_early_requeue_pi_wakeup() Thomas Gleixner
2021-08-11 12:23 ` [patch V4 64/68] futex: Prevent requeue_pi() lock nesting issue on RT Thomas Gleixner
2021-08-11 12:23 ` [patch V4 65/68] rtmutex: Prevent lockdep false positive with PI futexes Thomas Gleixner
2021-08-11 12:23 ` [patch V4 66/68] preempt: Adjust PREEMPT_LOCK_OFFSET for RT Thomas Gleixner
2021-08-11 12:23 ` [patch V4 67/68] locking/rtmutex: Implement equal priority lock stealing Thomas Gleixner
2021-08-11 12:23 ` [patch V4 68/68] locking/rtmutex: Add adaptive spinwait mechanism Thomas Gleixner
2021-08-13 8:05 ` [patch V4 69/68] locking/rt: Add missing __might_sleep() to spin/rwlocks Thomas Gleixner
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