tree 09ec78a9cfa751ce36288c32c4e5112f34af8582
parent 8315f42295d2667a7f942f154b73a86fd7cb2227
author Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1404239217 -0700
committer Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1410132440 -0700

rcu: Provide cond_resched_rcu_qs() to force quiescent states in long loops

RCU-tasks requires the occasional voluntary context switch
from CPU-bound in-kernel tasks.  In some cases, this requires
instrumenting cond_resched().  However, there is some reluctance
to countenance unconditionally instrumenting cond_resched() (see
http://lwn.net/Articles/603252/), so this commit creates a separate
cond_resched_rcu_qs() that may be used in place of cond_resched() in
locations prone to long-duration in-kernel looping.

This commit currently instruments only RCU-tasks.  Future possibilities
include also instrumenting RCU, RCU-bh, and RCU-sched in order to reduce
IPI usage.

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