diff mbox

[tip/core/rcu,12/14] rcu: Prevent __call_rcu() from invoking RCU core on offline CPUs

Message ID 1339791195-26389-12-git-send-email-paulmck@linux.vnet.ibm.com
State Superseded
Headers show

Commit Message

Paul E. McKenney June 15, 2012, 8:13 p.m. UTC 
From: "Paul E. McKenney" <paul.mckenney@linaro.org>

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 <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcutree.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

Comments

Josh Triplett June 15, 2012, 9:04 p.m. UTC | #1 
On Fri, Jun 15, 2012 at 01:13:13PM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paul.mckenney@linaro.org>
> 
> 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 <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 |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index 7720177..9419ebf 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -1901,11 +1901,11 @@ __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;
>  	}
> -- 
> 1.7.8
>
diff mbox

Patch

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 7720177..9419ebf 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1901,11 +1901,11 @@  __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;
 	}