Commit-ID: f7be82093952ee4a74ffc8c729b2811f908cd9a4
Gitweb: http://git.kernel.org/tip/f7be82093952ee4a74ffc8c729b2811f908cd9a4
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 8 Aug 2013 18:27:52 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 23 Sep 2013 09:16:10 -0700
rcu: Improve grace-period start logic
This commit improves grace-period start logic by checking ->gp_flags
under the lock and by issuing a warning if a grace period is already
in progress.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcutree.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 32618b3..d679a52 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1297,7 +1297,7 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
}
/*
- * Initialize a new grace period.
+ * Initialize a new grace period. Return 0 if no grace period required.
*/
static int rcu_gp_init(struct rcu_state *rsp)
{
@@ -1306,10 +1306,18 @@ static int rcu_gp_init(struct rcu_state *rsp)
rcu_bind_gp_kthread();
raw_spin_lock_irq(&rnp->lock);
+ if (rsp->gp_flags == 0) {
+ /* Spurious wakeup, tell caller to go back to sleep. */
+ raw_spin_unlock_irq(&rnp->lock);
+ return 0;
+ }
rsp->gp_flags = 0; /* Clear all flags: New grace period. */
- if (rcu_gp_in_progress(rsp)) {
- /* Grace period already in progress, don't start another. */
+ if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) {
+ /*
+ * Grace period already in progress, don't start another.
+ * Not supposed to be able to happen.
+ */
raw_spin_unlock_irq(&rnp->lock);
return 0;
}
@@ -1474,8 +1482,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
wait_event_interruptible(rsp->gp_wq,
rsp->gp_flags &
RCU_GP_FLAG_INIT);
- if ((rsp->gp_flags & RCU_GP_FLAG_INIT) &&
- rcu_gp_init(rsp))
+ if (rcu_gp_init(rsp))
break;
cond_resched();
flush_signals(current);
--
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