tree 1b92eacb707befb294b4d9985f10aa44715cba16
parent b0d304172f49061b4ff78f9e2b02719ac69c8a7e
author Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1310893549 -0700
committer Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1311136731 -0700

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>