rcu: Fix accelerated grace periods for last non-dynticked CPU

It is invalid to invoke __rcu_process_callbacks() with irqs
disabled, so do it indirectly via raise_softirq().  This
requires a state-machine implementation to cycle through the
grace-period machinery the required number of times.

Located-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1267231138-27856-1-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 335bfe4f0076..3ec8160fc75f 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1341,6 +1341,9 @@ static void rcu_process_callbacks(struct softirq_action *unused)
          * grace-period manipulations above.
          */
         smp_mb(); /* See above block comment. */
+
+        /* If we are last CPU on way to dyntick-idle mode, accelerate it. */
+        rcu_needs_cpu_flush();
 }
 
 static void