From 5342e269b2b58ee0b0b4168a94087faaa60d0567 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 16 Aug 2011 17:46:46 -0700 Subject: rcu: Permit rt_mutex_unlock() with irqs disabled Create a separate lockdep class for the rt_mutex used for RCU priority boosting and enable use of rt_mutex_lock() with irqs disabled. This prevents RCU priority boosting from falling prey to deadlocks when someone begins an RCU read-side critical section in preemptible state, but releases it with an irq-disabled lock held. Unfortunately, the scheduler's runqueue and priority-inheritance locks still must either completely enclose or be completely enclosed by any overlapping RCU read-side critical section. This version removes a redundant local_irq_restore() noted by Yong Zhang. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- kernel/rtmutex.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'kernel/rtmutex.c') diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c index 255e1662acdb..5e8d9cce7470 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -579,6 +579,7 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, struct rt_mutex_waiter *waiter) { int ret = 0; + int was_disabled; for (;;) { /* Try to acquire the lock: */ @@ -601,10 +602,17 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, raw_spin_unlock(&lock->wait_lock); + was_disabled = irqs_disabled(); + if (was_disabled) + local_irq_enable(); + debug_rt_mutex_print_deadlock(waiter); schedule_rt_mutex(lock); + if (was_disabled) + local_irq_disable(); + raw_spin_lock(&lock->wait_lock); set_current_state(state); } -- cgit v1.2.3