lkml.org 
[lkml]   [2012]   [Aug]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH tip/core/rcu 16/26] alpha: Add missing RCU idle APIs on idle loop
    On Thu, Aug 30, 2012 at 02:05:33PM -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 Alpha's idle loop.
    >
    > Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    > Cc: Richard Henderson <rth@twiddle.net>
    > Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
    > Cc: Matt Turner <mattst88@gmail.com>
    > Cc: alpha <linux-alpha@vger.kernel.org>
    > Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    > Cc: Michael Cree <mcree@orcon.net.nz>
    > Cc: 3.2.x.. <stable@vger.kernel.org>

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

    > arch/alpha/kernel/process.c | 3 +++
    > 1 files changed, 3 insertions(+), 0 deletions(-)
    >
    > diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c
    > index eac5e01..eb9558c 100644
    > --- a/arch/alpha/kernel/process.c
    > +++ b/arch/alpha/kernel/process.c
    > @@ -28,6 +28,7 @@
    > #include <linux/tty.h>
    > #include <linux/console.h>
    > #include <linux/slab.h>
    > +#include <linux/rcupdate.h>
    >
    > #include <asm/reg.h>
    > #include <asm/uaccess.h>
    > @@ -54,9 +55,11 @@ cpu_idle(void)
    > /* FIXME -- EV6 and LCA45 know how to power down
    > the CPU. */
    >
    > + rcu_idle_enter();
    > while (!need_resched())
    > cpu_relax();
    >
    > + rcu_idle_exit();
    > schedule_preempt_disabled();
    > }
    > }
    > --
    > 1.7.8
    >


    \
     
     \ /
      Last update: 2012-09-01 03:01    [W:4.031 / U:1.444 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site