From: Paul E. McKenney Date: Sat, 26 May 2012 15:56:01 +0000 (-0700) Subject: rcu: Prevent __call_rcu() from invoking RCU core on offline CPUs X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a16b7a693430406dc229ab0c6b154f669a2031c5;p=linux-beck.git rcu: Prevent __call_rcu() from invoking RCU core on offline CPUs The __call_rcu() function will invoke the RCU core, for example, if it detects that the current CPU has too many callbacks. However, this can happen on an offline CPU that is on its way to the idle loop, in which case it is an error to invoke the RCU core, and the excess callbacks will be adopted in any case. This commit therefore adds checks to __call_rcu() for running on an offline CPU, refraining from invoking the RCU core in this case. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- diff --git a/kernel/rcutree.c b/kernel/rcutree.c index a4a9c916ad36..ceaa95923a87 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1904,11 +1904,11 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), * If called from an extended quiescent state, invoke the RCU * core in order to force a re-evaluation of RCU's idleness. */ - if (rcu_is_cpu_idle()) + if (rcu_is_cpu_idle() && cpu_online(smp_processor_id())) invoke_rcu_core(); - /* If interrupts were disabled, don't dive into RCU core. */ - if (irqs_disabled_flags(flags)) { + /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ + if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) { local_irq_restore(flags); return; }