From: Paul E. McKenney <paul.mckenney@linaro.org>
Date: Wed, 17 Aug 2011 00:46:46 +0000 (-0700)
Subject: rcu: Permit rt_mutex_unlock() with irqs disabled
X-Git-Tag: v3.2-rc1~165^2^2~5
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5342e269b2b58ee0b0b4168a94087faaa60d0567;p=pandora-kernel.git

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 <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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