rcu: Prevent offline CPUs from executing RCU core code
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>
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index f0c0c1b..340a5f5 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1892,6 +1892,8 @@
{
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);