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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>
Subject: [patch 01/50] sched: Split out the wakeup state check
Date: Tue, 13 Jul 2021 17:10:55 +0200	[thread overview]
Message-ID: <20210713160745.984154587@linutronix.de> (raw)
In-Reply-To: <20210713151054.700719949@linutronix.de>

From: Thomas Gleixner <tglx@linutronix.de>

RT kernels have a slightly more complicated handling of wakeups due to
'sleeping' spin/rwlocks. If a task is blocked on such a lock then the
original state of the task is preserved over the blocking and any regular
(non lock related) wakeup has to be targeted at the saved state to ensure
that these wakeups are not lost. Once the task acquired the lock it
restores the task state from the saved state.

To avoid cluttering try_to_wake_up() with that logic, split the wake up
state check out into an inline helper and use it at both places where
task::state is checked against the state argument of try_to_wake_up().

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/sched/core.c |   24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)
---
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3564,6 +3564,22 @@ static void ttwu_queue(struct task_struc
 }
 
 /*
+ * Invoked from try_to_wake_up() to check whether the task can be woken up.
+ *
+ * The caller holds p::pi_lock if p != current or has preemption
+ * disabled when p == current.
+ */
+static __always_inline
+bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
+{
+	if (READ_ONCE(p->__state) & state) {
+		*success = 1;
+		return true;
+	}
+	return false;
+}
+
+/*
  * Notes on Program-Order guarantees on SMP systems.
  *
  *  MIGRATION
@@ -3702,10 +3718,9 @@ try_to_wake_up(struct task_struct *p, un
 		 *  - we're serialized against set_special_state() by virtue of
 		 *    it disabling IRQs (this allows not taking ->pi_lock).
 		 */
-		if (!(READ_ONCE(p->__state) & state))
+		if (!ttwu_state_match(p, state, &success))
 			goto out;
 
-		success = 1;
 		trace_sched_waking(p);
 		WRITE_ONCE(p->__state, TASK_RUNNING);
 		trace_sched_wakeup(p);
@@ -3720,14 +3735,11 @@ try_to_wake_up(struct task_struct *p, un
 	 */
 	raw_spin_lock_irqsave(&p->pi_lock, flags);
 	smp_mb__after_spinlock();
-	if (!(READ_ONCE(p->__state) & state))
+	if (!ttwu_state_match(p, state, &success))
 		goto unlock;
 
 	trace_sched_waking(p);
 
-	/* We're going to change ->state: */
-	success = 1;
-
 	/*
 	 * Ensure we load p->on_rq _after_ p->state, otherwise it would
 	 * be possible to, falsely, observe p->on_rq == 0 and get stuck


  reply	other threads:[~2021-07-13 16:13 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-13 15:10 [patch 00/50] locking, sched: The PREEMPT-RT locking infrastructure Thomas Gleixner
2021-07-13 15:10 ` Thomas Gleixner [this message]
2021-07-13 15:10 ` [patch 02/50] sched: Introduce TASK_RTLOCK_WAIT Thomas Gleixner
2021-07-13 15:10 ` [patch 03/50] sched: Prepare for RT sleeping spin/rwlocks Thomas Gleixner
2021-07-13 19:52   ` Waiman Long
2021-07-14 23:20   ` Valentin Schneider
2021-07-15  9:27     ` Peter Zijlstra
2021-07-15 14:08       ` Valentin Schneider
2021-07-13 15:10 ` [patch 04/50] sched: Rework the __schedule() preempt argument Thomas Gleixner
2021-07-13 20:04   ` Waiman Long
2021-07-13 15:10 ` [patch 05/50] sched: Provide schedule point for RT locks Thomas Gleixner
2021-07-14  8:28   ` Peter Zijlstra
2021-07-14  9:49     ` Thomas Gleixner
2021-07-14 10:17       ` Peter Zijlstra
2021-07-14 11:32         ` Thomas Gleixner
2021-07-13 15:11 ` [patch 06/50] sched/wake_q: Provide WAKE_Q_HEAD_INITIALIZER Thomas Gleixner
2021-07-13 15:11 ` [patch 07/50] rtmutex: Convert macros to inlines Thomas Gleixner
2021-07-13 15:11 ` [patch 08/50] rtmutex: Switch to try_cmpxchg() Thomas Gleixner
2021-07-13 15:11 ` [patch 09/50] rtmutex: Split API and implementation Thomas Gleixner
2021-07-13 15:11 ` [patch 10/50] locking/rtmutex: Provide rt_mutex_slowlock_locked() Thomas Gleixner
2021-07-27 17:20   ` Valentin Schneider
2021-07-27 19:02     ` Thomas Gleixner
2021-07-13 15:11 ` [patch 11/50] locking/rtmutex: Provide lockdep less variants of rtmutex interfaces Thomas Gleixner
2021-07-13 15:11 ` [patch 12/50] locking: Add base code for RT rw_semaphore and rwlock Thomas Gleixner
2021-07-13 15:11 ` [patch 13/50] locking/rwsem: Add rtmutex based R/W semaphore implementation Thomas Gleixner
2021-07-13 15:11 ` [patch 14/50] locking/rtmutex: Add wake_state to rt_mutex_waiter Thomas Gleixner
2021-07-14 10:18   ` Peter Zijlstra
2021-07-14 11:33     ` Thomas Gleixner
2021-07-13 15:11 ` [patch 15/50] locking/rtmutex: Provide rt_mutex_wake_q and helpers Thomas Gleixner
2021-07-13 15:11 ` [patch 16/50] locking/rtmutex: Use rt_mutex_wake_q_head Thomas Gleixner
2021-07-14  8:55   ` Peter Zijlstra
2021-07-14  9:51     ` Thomas Gleixner
2021-07-13 15:11 ` [patch 17/50] locking/rtmutex: Prepare RT rt_mutex_wake_q for RT locks Thomas Gleixner
2021-07-14  8:55   ` Peter Zijlstra
2021-07-14  9:52     ` Thomas Gleixner
2021-07-13 15:11 ` [patch 18/50] locking/rtmutex: Guard regular sleeping locks specific functions Thomas Gleixner
2021-07-13 15:11 ` [patch 19/50] locking/spinlock: Split the lock types header Thomas Gleixner
2021-07-13 15:11 ` [patch 20/50] locking/rtmutex: Prevent future include recursion hell Thomas Gleixner
2021-07-13 15:11 ` [patch 21/50] locking/lockdep: Reduce includes in debug_locks.h Thomas Gleixner
2021-07-13 15:11 ` [patch 22/50] rbtree: Split out the rbtree type definitions Thomas Gleixner
2021-07-14  9:24   ` Peter Zijlstra
2021-07-14  9:31     ` Arnaldo
2021-07-13 15:11 ` [patch 23/50] locking/rtmutex: Include only rbtree types Thomas Gleixner
2021-07-13 15:11 ` [patch 24/50] locking/spinlock: Provide RT specific spinlock type Thomas Gleixner
2021-07-14  9:54   ` Peter Zijlstra
2021-07-14 10:07     ` [PATCH] media/atomisp: Use lockdep instead of *mutex_is_locked() Peter Zijlstra
2021-07-13 15:11 ` [patch 25/50] locking/spinlock: Provide RT variant header Thomas Gleixner
2021-07-13 15:11 ` [patch 26/50] locking/rtmutex: Provide the spin/rwlock core lock function Thomas Gleixner
2021-07-14 10:59   ` Peter Zijlstra
2021-07-13 15:11 ` [patch 27/50] locking/spinlock: Provide RT variant Thomas Gleixner
2021-07-14 11:25   ` Peter Zijlstra
2021-07-13 15:11 ` [patch 28/50] locking/rwlock: " Thomas Gleixner
2021-07-13 15:11 ` [patch 29/50] locking/mutex: Consolidate core headers Thomas Gleixner
2021-07-13 15:11 ` [patch 30/50] locking/mutex: Move waiter to core header Thomas Gleixner
2021-07-13 15:11 ` [patch 31/50] locking/ww_mutex: Move ww_mutex declarations into ww_mutex.h Thomas Gleixner
2021-07-13 15:11 ` [patch 32/50] locking/mutex: Make mutex::wait_lock raw Thomas Gleixner
2021-07-13 15:11 ` [patch 33/50] locking/mutex: Introduce _mutex_t Thomas Gleixner
2021-07-15 17:31   ` Peter Zijlstra
2021-07-13 15:11 ` [patch 34/50] locking/mutex: Rename the ww_mutex relevant functions Thomas Gleixner
2021-07-13 15:11 ` [patch 35/50] locking/ww_mutex: Switch to _mutex_t Thomas Gleixner
2021-07-13 15:11 ` [patch 36/50] locking/mutex: Replace struct mutex in core code Thomas Gleixner
2021-07-13 15:11 ` [patch 37/50] locking/mutex: Rearrange items in mutex.h Thomas Gleixner
2021-07-13 15:11 ` [patch 38/50] locking/mutex: Exclude non-ww_mutex API for RT Thomas Gleixner
2021-07-13 15:11 ` [patch 39/50] locking/rtmutex: Add mutex variant " Thomas Gleixner
2021-07-13 15:11 ` [patch 40/50] lib/test_lockup: Adapt to changed variables Thomas Gleixner
2021-07-13 15:11 ` [patch 41/50] futex: Validate waiter correctly in futex_proxy_trylock_atomic() Thomas Gleixner
2021-07-13 15:11 ` [patch 42/50] futex: Cleanup stale comments Thomas Gleixner
2021-07-28 23:28   ` André Almeida
2021-07-13 15:11 ` [patch 43/50] futex: Correct the number of requeued waiters for PI Thomas Gleixner
2021-07-13 15:11 ` [patch 44/50] futex: Restructure futex_requeue() Thomas Gleixner
2021-07-13 15:11 ` [patch 45/50] futex: Clarify comment in futex_requeue() Thomas Gleixner
2021-07-13 15:11 ` [patch 46/50] futex: Prevent requeue_pi() lock nesting issue on RT Thomas Gleixner
2021-07-13 15:11 ` [patch 47/50] rtmutex: Prevent lockdep false positive with PI futexes Thomas Gleixner
2021-07-13 15:11 ` [patch 48/50] preempt: Adjust PREEMPT_LOCK_OFFSET for RT Thomas Gleixner
2021-07-13 15:11 ` [patch 49/50] locking/rtmutex: Implement equal priority lock stealing Thomas Gleixner
2021-07-13 15:11 ` [patch 50/50] locking/rtmutex: Add adaptive spinwait mechanism Thomas Gleixner
2021-07-27 17:19 ` [patch 00/50] locking, sched: The PREEMPT-RT locking infrastructure Valentin Schneider

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