tree 601697c7c3fd152a1b3f29f43d3a028fc8fefd5f
parent 12f5f524cafef3ab689929b118f2dfb8bf2be321
author Paul E. McKenney <paul.mckenney@linaro.org> 1294870223 -0800
committer Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1304662614 -0700

rcu: move TREE_RCU from softirq to kthread

If RCU priority boosting is to be meaningful, callback invocation must
be boosted in addition to preempted RCU readers.  Otherwise, in presence
of CPU real-time threads, the grace period ends, but the callbacks don't
get invoked.  If the callbacks don't get invoked, the associated memory
doesn't get freed, so the system is still subject to OOM.

But it is not reasonable to priority-boost RCU_SOFTIRQ, so this commit
moves the callback invocations to a kthread, which can be boosted easily.

Also add comments and properly synchronized all accesses to
rcu_cpu_kthread_task, as suggested by Lai Jiangshan.

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