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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>
This commit is contained in:
Paul E. McKenney 2012-06-21 09:54:10 -07:00 committed by Paul E. McKenney
parent 7fdefc10e1
commit bfa00b4c40
1 changed files with 2 additions and 0 deletions
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2
kernel/rcutree.c
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@ -1892,6 +1892,8 @@ 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);