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    SubjectRe: [PATCH tip/core/rcu 19/26] h8300: Add missing RCU idle APIs on idle loop
    On Thu, Aug 30, 2012 at 02:05:36PM -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 h8300's idle loop.
    >
    > Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    > Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
    > 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/h8300/kernel/process.c | 3 +++
    > 1 files changed, 3 insertions(+), 0 deletions(-)
    >
    > diff --git a/arch/h8300/kernel/process.c b/arch/h8300/kernel/process.c
    > index 0e9c315..f153ed1 100644
    > --- a/arch/h8300/kernel/process.c
    > +++ b/arch/h8300/kernel/process.c
    > @@ -36,6 +36,7 @@
    > #include <linux/reboot.h>
    > #include <linux/fs.h>
    > #include <linux/slab.h>
    > +#include <linux/rcupdate.h>
    >
    > #include <asm/uaccess.h>
    > #include <asm/traps.h>
    > @@ -78,8 +79,10 @@ void (*idle)(void) = default_idle;
    > void cpu_idle(void)
    > {
    > while (1) {
    > + rcu_idle_enter();
    > while (!need_resched())
    > idle();
    > + rcu_idle_exit();
    > schedule_preempt_disabled();
    > }
    > }
    > --
    > 1.7.8
    >


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