linux-kernel - [PATCH 3.2 186/200] printk: Fix scheduling-while-atomic problem in console_cpu

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Message-ID: <lsq.1396221815.342630344@decadent.org.uk>
Date:	Mon, 31 Mar 2014 00:23:35 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH 3.2 186/200] printk: Fix scheduling-while-atomic problem
 in console_cpu_notify()

3.2.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

commit 85eae82a0855d49852b87deac8653e4ebc8b291f upstream.

The console_cpu_notify() function runs with interrupts disabled in the
CPU_DYING case.  It therefore cannot block, for example, as will happen
when it calls console_lock().  Therefore, remove the CPU_DYING leg of
the switch statement to avoid this problem.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/printk.c | 1 -
 1 file changed, 1 deletion(-)

--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1165,7 +1165,6 @@ static int __cpuinit console_cpu_notify(
 	switch (action) {
 	case CPU_ONLINE:
 	case CPU_DEAD:
-	case CPU_DYING:
 	case CPU_DOWN_FAILED:
 	case CPU_UP_CANCELED:
 		console_lock();

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