blob: 6fe021d65f0a2b0051666bc96a4c3bb4e6093485 [file] [log] [blame]
From 04915f95519eedd70dd247794358b3136a4000f3 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 1 Mar 2013 11:17:42 +0100
Subject: [PATCH] futex: Ensure lock/unlock symetry versus pi_lock and hash
bucket lock
In exit_pi_state_list() we have the following locking construct:
spin_lock(&hb->lock);
raw_spin_lock_irq(&curr->pi_lock);
...
spin_unlock(&hb->lock);
In !RT this works, but on RT the migrate_enable() function which is
called from spin_unlock() sees atomic context due to the held pi_lock
and just decrements the migrate_disable_atomic counter of the
task. Now the next call to migrate_disable() sees the counter being
negative and issues a warning. That check should be in
migrate_enable() already.
Fix this by dropping pi_lock before unlocking hb->lock and reaquire
pi_lock after that again. This is safe as the loop code reevaluates
head again under the pi_lock.
Reported-by: Yong Zhang <yong.zhang@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
diff --git a/kernel/futex.c b/kernel/futex.c
index bebcc1a0dcf7..8633f667560e 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -917,7 +917,9 @@ void exit_pi_state_list(struct task_struct *curr)
*/
if (head->next != next) {
raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
+ raw_spin_unlock_irq(&curr->pi_lock);
spin_unlock(&hb->lock);
+ raw_spin_lock_irq(&curr->pi_lock);
continue;
}
--
2.15.0