[PATCH 10/16] rcu: Check for RCU_FLAG_GP_INIT bit in gp_flags for spurious wakeup

Pranith Kumar
2014-07-23T05:11:04Z

rcu_gp_init() is called once the gp_kthread wakes up on the condition that
the init bit is set in the gp_flags. For a spurious wakeup we need to check that
it is actually set. This commit ensures that the RCU_GP_FLAG_INIT bit is set in
gp_flags.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
---
kernel/rcu/tree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8d598a2..f8847d9 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1600,7 +1600,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
rcu_bind_gp_kthread();
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
- if (!ACCESS_ONCE(rsp->gp_flags)) {
+ if (!(ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_INIT)) {
/* Spurious wakeup, tell caller to go back to sleep. */
raw_spin_unlock_irq(&rnp->lock);
return 0;
--
2.0.0.rc2