From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Sun, 17 Jul 2011 09:05:49 +0000 (-0700)
Subject: rcu: decrease rcu_report_exp_rnp coupling with scheduler
X-Git-Tag: v3.0~7^2^2~6
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=131906b0062ddde7f85bbe67754983c754648bd8;p=pandora-kernel.git

rcu: decrease rcu_report_exp_rnp coupling with scheduler

PREEMPT_RCU read-side critical sections blocking an expedited grace
period invoke rcu_report_exp_rnp().  When the last such critical section
has completed, rcu_report_exp_rnp() invokes the scheduler to wake up the
task that invoked synchronize_rcu_expedited() -- needlessly holding the
root rcu_node structure's lock while doing so, thus needlessly providing
a way for RCU and the scheduler to deadlock.

This commit therefore releases the root rcu_node structure's lock before
calling wake_up().

Reported-by: Ed Tomlinson <edt@aei.ca>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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