linux-kernel - [PATCH] notifiers: Assert that RCU is watching in notify

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Message-Id: <8a544ca7ba99a9a64ef83df065a75eaefcf2851f.1433463380.git.luto@kernel.org>
Date:	Thu,  4 Jun 2015 17:17:06 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	mingo@...nel.org
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH] notifiers: Assert that RCU is watching in notify_die

Low-level arch entries often call notify_die, and it's easy for arch
code to fail to exit an RCU quiescent state first.  Assert that
we're not quiescent in notify_die.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 kernel/notifier.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/notifier.c b/kernel/notifier.c
index ae9fc7cc360e..980e4330fb59 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -544,6 +544,8 @@ int notrace notify_die(enum die_val val, const char *str,
 		.signr	= sig,
 
 	};
+	rcu_lockdep_assert(rcu_is_watching(),
+			   "notify_die called but RCU thinks we're quiescent");
 	return atomic_notifier_call_chain(&die_chain, val, &args);
 }
 NOKPROBE_SYMBOL(notify_die);
-- 
2.4.2

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