[PATCH tip/core/rcu 4/7] rcu: Refine diagnostics for lacking kthread for no-CBs callbacks

From: Paul E. McKenney
Date: Tue Mar 03 2015 - 11:46:28 EST


From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>

Some diagnostics under CONFIG_PROVE_RCU in rcu_nocb_cpu_needs_barrier()
assume that there can be no early-boot callbacks. This commit therefore
qualifies the diagnostic with rcu_scheduler_fully_active to permit
early boot callbacks to avoid this splat.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree_plugin.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 0a571e9a0f1d..75d5f096bcb0 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1945,7 +1945,8 @@ static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu)
rhp = ACCESS_ONCE(rdp->nocb_follower_head);

/* Having no rcuo kthread but CBs after scheduler starts is bad! */
- if (!ACCESS_ONCE(rdp->nocb_kthread) && rhp) {
+ if (!ACCESS_ONCE(rdp->nocb_kthread) && rhp &&
+ rcu_scheduler_fully_active) {
/* RCU callback enqueued before CPU first came online??? */
pr_err("RCU: Never-onlined no-CBs CPU %d has CB %p\n",
cpu, rhp->func);
--
1.8.1.5

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