linux-kernel - [PATCH 1/9] jump label: notifier atomic call chain notrace

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Date:	Fri, 9 Apr 2010 15:49:20 -0400
From:	Jason Baron <jbaron@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, mathieu.desnoyers@...ymtl.ca, hpa@...or.com,
	tglx@...utronix.de, rostedt@...dmis.org, andi@...stfloor.org,
	roland@...hat.com, rth@...hat.com, mhiramat@...hat.com,
	fweisbec@...il.com, avi@...hat.com
Subject: [PATCH 1/9] jump label: notifier atomic call chain notrace

In LTTng, being able to use the atomic notifier from cpu idle entry to
ensure the tracer flush the last events in the current subbuffer
requires the rcu read-side to be marked "notrace", otherwise it can end
up calling back into lockdep and the tracer.

Also apply to the the die notifier.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Signed-off-by: Jason Baron <jbaron@...hat.com>
Reviewed-by: Masami Hiramatsu <mhiramat@...hat.com>
---
 kernel/notifier.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/notifier.c b/kernel/notifier.c
index 2488ba7..88453a7 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -148,7 +148,7 @@ int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
 	spin_lock_irqsave(&nh->lock, flags);
 	ret = notifier_chain_unregister(&nh->head, n);
 	spin_unlock_irqrestore(&nh->lock, flags);
-	synchronize_rcu();
+	synchronize_sched();
 	return ret;
 }
 EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
@@ -178,9 +178,9 @@ int __kprobes __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
 {
 	int ret;
 
-	rcu_read_lock();
+	rcu_read_lock_sched_notrace();
 	ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
-	rcu_read_unlock();
+	rcu_read_unlock_sched_notrace();
 	return ret;
 }
 EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
-- 
1.7.0.1

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