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[tip/core/rcu,07/23] rcu: Prevent offline CPUs from executing RCU core code

Message ID 1348166900-18716-7-git-send-email-paulmck@linux.vnet.ibm.com
State Accepted
Commit bfa00b4c4028f39357d16279ff0fddf550241593
Headers show

Commit Message

Paul E. McKenney Sept. 20, 2012, 6:48 p.m. UTC 
From: "Paul E. McKenney" <paul.mckenney@linaro.org>

Earlier versions of RCU invoked the RCU core from the CPU_DYING notifier
in order to note a quiescent state for the outgoing CPU.  Because the
CPU is marked "offline" during the execution of the CPU_DYING notifiers,
the RCU core had to tolerate being invoked from an offline CPU.  However,
commit b1420f1c (Make rcu_barrier() less disruptive) left only tracing
code in the CPU_DYING notifier, so the RCU core need no longer execute
on offline CPUs.  This commit therefore enforces this restriction.

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>
---
 kernel/rcutree.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
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Patch

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index f061740..c5938e8 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1890,6 +1890,8 @@  static void rcu_process_callbacks(struct softirq_action *unused)
 {
 	struct rcu_state *rsp;
 
+	if (cpu_is_offline(smp_processor_id()))
+		return;
 	trace_rcu_utilization("Start RCU core");
 	for_each_rcu_flavor(rsp)
 		__rcu_process_callbacks(rsp);