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authorFrederic Weisbecker <fweisbec@gmail.com>2012-08-22 17:27:34 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-10-13 05:38:54 +0900
commit3b30d3182fbf026578fbad09877d78c338562f4c (patch)
tree099cf7fb012c1ecb90b20cdd54673e42e149f501
parentce6ccabd21d356ac22973d275f122d3d8efc96d7 (diff)
downloadlwn-3b30d3182fbf026578fbad09877d78c338562f4c.tar.gz
lwn-3b30d3182fbf026578fbad09877d78c338562f4c.zip
alpha: Add missing RCU idle APIs on idle loop
commit 4c94cada48f7c660eca582be6032427a5e367117 upstream. 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> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/alpha/kernel/process.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c
index 153d3fce3e8e..8e3d91be76b0 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>
@@ -54,8 +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();
}
}