From: Mike Galbraith <efault@gmx.de>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>
Subject: [patch-rt] locking, rwlock-rt: do not save state multiple times in __write_rt_lock()
Date: Wed, 09 Aug 2017 14:04:48 +0200 [thread overview]
Message-ID: <1502280288.6441.3.camel@gmx.de> (raw)
In-Reply-To: <1502095134.5568.27.camel@gmx.de>
Save state prior to entering the acquisition loop, otherwise we may
initially see readers, but upon releasing ->wait_lock see none, loop
back around, and having not slept, save TASK_UNINTERRUPTIBLE.
Signed-off-by_ Mike Galbraith <efault@gmx.de>
---
kernel/locking/rwlock-rt.c | 37 ++++++++++++++++++++-----------------
1 file changed, 20 insertions(+), 17 deletions(-)
--- a/kernel/locking/rwlock-rt.c
+++ b/kernel/locking/rwlock-rt.c
@@ -190,30 +190,33 @@ void __sched __write_rt_lock(struct rt_r
/* Force readers into slow path */
atomic_sub(READER_BIAS, &lock->readers);
- for (;;) {
- raw_spin_lock_irqsave(&m->wait_lock, flags);
-
- raw_spin_lock(&self->pi_lock);
- self->saved_state = self->state;
- __set_current_state_no_track(TASK_UNINTERRUPTIBLE);
- raw_spin_unlock(&self->pi_lock);
+ raw_spin_lock_irqsave(&m->wait_lock, flags);
+ raw_spin_lock(&self->pi_lock);
+ self->saved_state = self->state;
+ __set_current_state_no_track(TASK_UNINTERRUPTIBLE);
+ raw_spin_unlock(&self->pi_lock);
+ for (;;) {
/* Have all readers left the critical region? */
- if (!atomic_read(&lock->readers)) {
- atomic_set(&lock->readers, WRITER_BIAS);
- raw_spin_lock(&self->pi_lock);
- __set_current_state_no_track(self->saved_state);
- self->saved_state = TASK_RUNNING;
- raw_spin_unlock(&self->pi_lock);
- raw_spin_unlock_irqrestore(&m->wait_lock, flags);
- return;
- }
+ if (!atomic_read(&lock->readers))
+ break;
raw_spin_unlock_irqrestore(&m->wait_lock, flags);
-
if (atomic_read(&lock->readers) != 0)
schedule();
+ raw_spin_lock_irqsave(&m->wait_lock, flags);
+
+ raw_spin_lock(&self->pi_lock);
+ __set_current_state_no_track(TASK_UNINTERRUPTIBLE);
+ raw_spin_unlock(&self->pi_lock);
}
+
+ atomic_set(&lock->readers, WRITER_BIAS);
+ raw_spin_lock(&self->pi_lock);
+ __set_current_state_no_track(self->saved_state);
+ self->saved_state = TASK_RUNNING;
+ raw_spin_unlock(&self->pi_lock);
+ raw_spin_unlock_irqrestore(&m->wait_lock, flags);
}
int __write_rt_trylock(struct rt_rw_lock *lock)
next prev parent reply other threads:[~2017-08-09 12:05 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-04 17:38 [ANNOUNCE] v4.11.12-rt9 Sebastian Andrzej Siewior
2017-08-05 6:13 ` Mike Galbraith
2017-08-05 14:57 ` Mike Galbraith
2017-08-07 7:33 ` Sebastian Andrzej Siewior
2017-08-07 8:22 ` Mike Galbraith
2017-08-08 10:00 ` Mike Galbraith
2017-08-11 7:55 ` [patch-rt] hotplug, hrtimer: Migrate expired/deferred timers during cpu offline Mike Galbraith
2017-08-11 8:15 ` Mike Galbraith
2017-08-14 7:59 ` Mike Galbraith
2017-08-17 16:50 ` Sebastian Andrzej Siewior
2017-08-17 17:17 ` Sebastian Andrzej Siewior
2017-08-17 17:26 ` Mike Galbraith
2017-08-17 17:37 ` Mike Galbraith
2017-08-17 18:43 ` Mike Galbraith
2017-08-07 7:52 ` [ANNOUNCE] v4.11.12-rt9 Sebastian Andrzej Siewior
2017-08-07 8:38 ` Mike Galbraith
2017-08-09 12:04 ` Mike Galbraith [this message]
2017-08-18 9:06 ` [patch-rt] locking, rwlock-rt: do not save state multiple times in __write_rt_lock() Sebastian Andrzej Siewior
2017-08-07 9:10 ` [ANNOUNCE] v4.11.12-rt9 Mike Galbraith
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