Commit-ID: 143da9c2fc030a5774674f2ebc2f934fab3dcd9a
Gitweb: http://git.kernel.org/tip/143da9c2fc030a5774674f2ebc2f934fab3dcd9a
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 19 Jan 2015 19:57:32 -0800
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 26 Feb 2015 12:01:28 -0800
rcu: Prevent early-boot RCU callbacks from splatting
Currently, a call_rcu() that precedes rcu_init() will splat due to the
callback lists not having yet been initialized. This commit causes the
first such callback to initialize the boot CPU's RCU callback list.
Note that this commit does not change rcu_init()-time initialization,
which means that the callback will be discarded at rcu_init() time.
Fixing this is the job of later commits.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index d2fa95e..fcfdbe5 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2838,11 +2838,21 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
if (cpu != -1)
rdp = per_cpu_ptr(rsp->rda, cpu);
- offline = !__call_rcu_nocb(rdp, head, lazy, flags);
- WARN_ON_ONCE(offline);
- /* _call_rcu() is illegal on offline CPU; leak the callback. */
- local_irq_restore(flags);
- return;
+ if (likely(rdp->mynode)) {
+ /* Post-boot, so this should be for a no-CBs CPU. */
+ offline = !__call_rcu_nocb(rdp, head, lazy, flags);
+ WARN_ON_ONCE(offline);
+ /* Offline CPU, _call_rcu() illegal, leak callback. */
+ local_irq_restore(flags);
+ return;
+ }
+ /*
+ * Very early boot, before rcu_init(). Initialize if needed
+ * and then drop through to queue the callback.
+ */
+ BUG_ON(cpu != -1);
+ if (!likely(rdp->nxtlist))
+ init_default_callback_list(rdp);
}
ACCESS_ONCE(rdp->qlen) = rdp->qlen + 1;
if (lazy)
--
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