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[tip/core/rcu,24/26] score: Add missing RCU idle APIs on idle loop

Message ID 1346360743-3628-24-git-send-email-paulmck@linux.vnet.ibm.com
State Accepted
Commit 0ee23fda59740767324b4340247ca41a2f498ca6
Headers show

Commit Message

Paul E. McKenney Aug. 30, 2012, 9:05 p.m. UTC 
From: Frederic Weisbecker <fweisbec@gmail.com>

In the old times, the whole idle task was considered
as an RCU quiescent state. But as RCU became more and
more successful overtime, some RCU read side critical
section have been added even in the code of some
architectures idle tasks, for tracing for example.

So nowadays, rcu_idle_enter() and rcu_idle_exit() must
be called by the architecture to tell RCU about the part
in the idle loop that doesn't make use of rcu read side
critical sections, typically the part that puts the CPU
in low power mode.

This is necessary for RCU to find the quiescent states in
idle in order to complete grace periods.

Add this missing pair of calls in the scores's idle loop.

Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Cc: Lennox Wu <lennox.wu@gmail.com>
Cc: 3.2.x.. <stable@vger.kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 arch/score/kernel/process.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

Comments

Josh Triplett Sept. 1, 2012, 12:04 a.m. UTC | #1 
On Thu, Aug 30, 2012 at 02:05:41PM -0700, Paul E. McKenney wrote:
> From: Frederic Weisbecker <fweisbec@gmail.com>
> 
> In the old times, the whole idle task was considered
> as an RCU quiescent state. But as RCU became more and
> more successful overtime, some RCU read side critical
> section have been added even in the code of some
> architectures idle tasks, for tracing for example.
> 
> So nowadays, rcu_idle_enter() and rcu_idle_exit() must
> be called by the architecture to tell RCU about the part
> in the idle loop that doesn't make use of rcu read side
> critical sections, typically the part that puts the CPU
> in low power mode.
> 
> This is necessary for RCU to find the quiescent states in
> idle in order to complete grace periods.
> 
> Add this missing pair of calls in the scores's idle loop.

s/scores's/score/ or s/the scores's/score's/

> Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Chen Liqin <liqin.chen@sunplusct.com>
> Cc: Lennox Wu <lennox.wu@gmail.com>
> Cc: 3.2.x.. <stable@vger.kernel.org>
> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

With the fix above,
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

>  arch/score/kernel/process.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/score/kernel/process.c b/arch/score/kernel/process.c
> index 2707023..637970c 100644
> --- a/arch/score/kernel/process.c
> +++ b/arch/score/kernel/process.c
> @@ -27,6 +27,7 @@
>  #include <linux/reboot.h>
>  #include <linux/elfcore.h>
>  #include <linux/pm.h>
> +#include <linux/rcupdate.h>
>  
>  void (*pm_power_off)(void);
>  EXPORT_SYMBOL(pm_power_off);
> @@ -50,9 +51,10 @@ void __noreturn cpu_idle(void)
>  {
>  	/* endless idle loop with no priority at all */
>  	while (1) {
> +		rcu_idle_enter();
>  		while (!need_resched())
>  			barrier();
> -
> +		rcu_idle_exit();
>  		schedule_preempt_disabled();
>  	}
>  }
> -- 
> 1.7.8
>
diff mbox

Patch

diff --git a/arch/score/kernel/process.c b/arch/score/kernel/process.c
index 2707023..637970c 100644
--- a/arch/score/kernel/process.c
+++ b/arch/score/kernel/process.c
@@ -27,6 +27,7 @@ 
 #include <linux/reboot.h>
 #include <linux/elfcore.h>
 #include <linux/pm.h>
+#include <linux/rcupdate.h>
 
 void (*pm_power_off)(void);
 EXPORT_SYMBOL(pm_power_off);
@@ -50,9 +51,10 @@  void __noreturn cpu_idle(void)
 {
 	/* endless idle loop with no priority at all */
 	while (1) {
+		rcu_idle_enter();
 		while (!need_resched())
 			barrier();
-
+		rcu_idle_exit();
 		schedule_preempt_disabled();
 	}
 }