Messages in this thread | | | Date | Fri, 31 Aug 2012 17:05:06 -0700 | From | Josh Triplett <> | Subject | Re: [PATCH tip/core/rcu 25/26] xtensa: Add missing RCU idle APIs on idle loop |
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On Thu, Aug 30, 2012 at 02:05:42PM -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 xtensa's idle loop. > > Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > Cc: Chris Zankel <chris@zankel.net> > 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/xtensa/kernel/process.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/arch/xtensa/kernel/process.c b/arch/xtensa/kernel/process.c > index 2c8d6a3..bc44311 100644 > --- a/arch/xtensa/kernel/process.c > +++ b/arch/xtensa/kernel/process.c > @@ -31,6 +31,7 @@ > #include <linux/mqueue.h> > #include <linux/fs.h> > #include <linux/slab.h> > +#include <linux/rcupdate.h> > > #include <asm/pgtable.h> > #include <asm/uaccess.h> > @@ -110,8 +111,10 @@ void cpu_idle(void) > > /* endless idle loop with no priority at all */ > while (1) { > + rcu_idle_enter(); > while (!need_resched()) > platform_idle(); > + rcu_idle_exit(); > schedule_preempt_disabled(); > } > } > -- > 1.7.8 >
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