Re: [PATCH tip/core/rcu 26/26] ia64: Add missing RCU idle APIs on idle loop

Josh Triplett
2012-09-01T00:05:33Z

On Thu, Aug 30, 2012 at 02:05:43PM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paul.mckenney@linaro.org>
>
> Traditionally, the entire idle task served as an RCU quiescent state.
> But when RCU read side critical sections started appearing within the
> idle loop, this traditional strategy became untenable. The fix was to
> create new RCU APIs named rcu_idle_enter() and rcu_idle_exit(), which
> must be called by each architecture's idle loop so that RCU can tell
> when it is safe to ignore a given idle CPU.
>
> Unfortunately, this fix was never applied to ia64, a shortcoming remedied
> by this commit.
>
> Reported by: Tony Luck <tony.luck@intel.com>
> Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Tested by: Tony Luck <tony.luck@intel.com>

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

> arch/ia64/kernel/process.c | 3 +++
> 1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
> index dd6fc14..3e316ec 100644
> --- a/arch/ia64/kernel/process.c
> +++ b/arch/ia64/kernel/process.c
> @@ -29,6 +29,7 @@
> #include <linux/kdebug.h>
> #include <linux/utsname.h>
> #include <linux/tracehook.h>
> +#include <linux/rcupdate.h>
>
> #include <asm/cpu.h>
> #include <asm/delay.h>
> @@ -279,6 +280,7 @@ cpu_idle (void)
>
> /* endless idle loop with no priority at all */
> while (1) {
> + rcu_idle_enter();
> if (can_do_pal_halt) {
> current_thread_info()->status &= ~TS_POLLING;
> /*
> @@ -309,6 +311,7 @@ cpu_idle (void)
> normal_xtp();
> #endif
> }
> + rcu_idle_exit();
> schedule_preempt_disabled();
> check_pgt_cache();
> if (cpu_is_offline(cpu))
> --
> 1.7.8
>