From: Paul E. McKenney Date: Tue, 12 Aug 2014 18:27:31 +0000 (-0700) Subject: rcu: Handle NOCB callbacks from irq-disabled idle code X-Git-Tag: firefly_0821_release~176^2~3065^2~1^2~16^3~1 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=1772947bd0126661866069157e95197e9c0020e9;p=firefly-linux-kernel-4.4.55.git rcu: Handle NOCB callbacks from irq-disabled idle code If an RCU callback is queued on a no-CBs CPU from idle code with irqs disabled, and if that CPU stays idle forever after, the callback will never be invoked. This commit therefore adds a check for this situation in ____call_rcu_nocb(), invoking the RCU core solely for the purpose of the ensuing return-to-idle transition. (If the CPU doesn't return to idle, the next scheduling-clock interrupt will fix things up.) Reported-by: Amit Shah Signed-off-by: Paul E. McKenney Tested-by: Paul Gortmaker --- diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 4ad63d861599..8b7351836228 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2129,6 +2129,17 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, trace_rcu_callback(rdp->rsp->name, rhp, -atomic_long_read(&rdp->nocb_q_count_lazy), -atomic_long_read(&rdp->nocb_q_count)); + + /* + * If called from an extended quiescent state with interrupts + * disabled, invoke the RCU core in order to allow the idle-entry + * deferred-wakeup check to function. + */ + if (irqs_disabled_flags(flags) && + !rcu_is_watching() && + cpu_online(smp_processor_id())) + invoke_rcu_core(); + return true; }