On Thu, Aug 30, 2012 at 02:05:40PM -0700, Paul E. McKenney wrote:
> From: Frederic Weisbecker <fweisbec@xxxxxxxxx>
>
> 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 parisc's idle loop.
>
> Reported-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Cc: James E.J. Bottomley <jejb@xxxxxxxxxxxxxxxx>
> Cc: Helge Deller <deller@xxxxxx>
> Cc: Parisc <linux-parisc@xxxxxxxxxxxxxxx>
> Cc: 3.2.x.. <stable@xxxxxxxxxxxxxxx>
> Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> arch/parisc/kernel/process.c | 3 +++
> 1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
> index d4b94b3..c54a4db 100644
> --- a/arch/parisc/kernel/process.c
> +++ b/arch/parisc/kernel/process.c
> @@ -48,6 +48,7 @@
> #include <linux/unistd.h>
> #include <linux/kallsyms.h>
> #include <linux/uaccess.h>
> +#include <linux/rcupdate.h>
>
> #include <asm/io.h>
> #include <asm/asm-offsets.h>
> @@ -69,8 +70,10 @@ void 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();
> check_pgt_cache();
> }
> --
> 1.7.8
>
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