[tip:core/rcu] rcu: Add diagnostic check for a possible CPU-hotplug race

[tip-bot for Paul E. McKenney]

Commit-ID:  7256cf0e83bf018be8a81806593aaef7f2437f0b
Gitweb:     http://git.kernel.org/tip/7256cf0e83bf018be8a81806593aaef7f2437f0b
Author:     Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Sun, 2 Aug 2009 10:21:10 -0700
Committer:  Ingo Molnar <mingo@xxxxxxx>
CommitDate: Sun, 2 Aug 2009 21:31:28 +0200

rcu: Add diagnostic check for a possible CPU-hotplug race

Complain if the RCU softirq code ever runs on a CPU that has
not yet been announced to RCU as being online.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
 kernel/rcutree.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 3313244..b9b1928 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1132,6 +1132,8 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
 {
 	unsigned long flags;
 
+	WARN_ON_ONCE(rdp->beenonline == 0);
+
 	/*
 	 * If an RCU GP has gone long enough, go check for dyntick
 	 * idle CPUs and, if needed, send resched IPIs.
--
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