cris: 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 Cris's idle loop.

Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Cris <linux-cris-kernel@axis.com>
Cc: <stable@vger.kernel.org> # 3.3+
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

diff --git a/arch/cris/kernel/process.c b/arch/cris/kernel/process.c
index 66fd01728790b3b63c5e6057e5a522ca71094f85..7f65be6f7f17741153222d11618a716593fbbb91 100644 (file)
--- a/arch/cris/kernel/process.c
+++ b/arch/cris/kernel/process.c
@@ -25,6 +25,7 @@
 #include <linux/elfcore.h>
 #include <linux/mqueue.h>
 #include <linux/reboot.h>
+#include <linux/rcupdate.h>
 
 //#define DEBUG
 
@@ -74,6 +75,7 @@ void cpu_idle (void)
 {
        /* endless idle loop with no priority at all */
        while (1) {
+               rcu_idle_enter();
                while (!need_resched()) {
                        void (*idle)(void);
                        /*
@@ -86,6 +88,7 @@ void cpu_idle (void)
                                idle = default_idle;
                        idle();
                }
+               rcu_idle_exit();
                schedule_preempt_disabled();
        }
 }