diff mbox

[tip/core/rcu,18/26] frv: Add missing RCU idle APIs on idle loop

Message ID 1346360743-3628-18-git-send-email-paulmck@linux.vnet.ibm.com
State Accepted
Commit 41d8fe5bb3cf91ce2716ac8f43e4b40d802a99c8
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 Frv's idle loop.

Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: 3.2.x.. <stable@vger.kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 arch/frv/kernel/process.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

Comments

Josh Triplett Sept. 1, 2012, 12:01 a.m. UTC | #1 
On Thu, Aug 30, 2012 at 02:05:35PM -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 Frv's idle loop.
> 
> Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: David Howells <dhowells@redhat.com>
> Cc: 3.2.x.. <stable@vger.kernel.org>
> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Reviewed-by: Josh Triplett <josh@joshtriplett.org>

>  arch/frv/kernel/process.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/frv/kernel/process.c b/arch/frv/kernel/process.c
> index ff95f50..2eb7fa5 100644
> --- a/arch/frv/kernel/process.c
> +++ b/arch/frv/kernel/process.c
> @@ -25,6 +25,7 @@
>  #include <linux/reboot.h>
>  #include <linux/interrupt.h>
>  #include <linux/pagemap.h>
> +#include <linux/rcupdate.h>
>  
>  #include <asm/asm-offsets.h>
>  #include <asm/uaccess.h>
> @@ -69,12 +70,14 @@ void cpu_idle(void)
>  {
>  	/* endless idle loop with no priority at all */
>  	while (1) {
> +		rcu_idle_enter();
>  		while (!need_resched()) {
>  			check_pgt_cache();
>  
>  			if (!frv_dma_inprogress && idle)
>  				idle();
>  		}
> +		rcu_idle_exit();
>  
>  		schedule_preempt_disabled();
>  	}
> -- 
> 1.7.8
>
diff mbox

Patch

diff --git a/arch/frv/kernel/process.c b/arch/frv/kernel/process.c
index ff95f50..2eb7fa5 100644
--- a/arch/frv/kernel/process.c
+++ b/arch/frv/kernel/process.c
@@ -25,6 +25,7 @@ 
 #include <linux/reboot.h>
 #include <linux/interrupt.h>
 #include <linux/pagemap.h>
+#include <linux/rcupdate.h>
 
 #include <asm/asm-offsets.h>
 #include <asm/uaccess.h>
@@ -69,12 +70,14 @@  void cpu_idle(void)
 {
 	/* endless idle loop with no priority at all */
 	while (1) {
+		rcu_idle_enter();
 		while (!need_resched()) {
 			check_pgt_cache();
 
 			if (!frv_dma_inprogress && idle)
 				idle();
 		}
+		rcu_idle_exit();
 
 		schedule_preempt_disabled();
 	}