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alpha: Add missing RCU idle APIs on idle loop 

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>
Tested-by: Michael Cree <mcree@orcon.net.nz>
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: <stable@vger.kernel.org> # 3.3+
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Frederic Weisbecker 2012-08-22 17:27:34 +02:00 committed by Paul E. McKenney
parent 6a6c0272f1
commit 4c94cada48
1 changed files with 3 additions and 0 deletions
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3
arch/alpha/kernel/process.c
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@ -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();
}
}