linux-kernel - [PATCH 1/4] printk: Disable preemption for printk

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Date:	Mon,  5 May 2014 13:47:41 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	John Stultz <john.stultz@...aro.org>, Jan Kara <jack@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiri Bohac <jbohac@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH 1/4] printk: Disable preemption for printk_sched

An earlier change in -mm (printk: remove separate printk_sched
buffers...), removed the printk_sched irqsave/restore lines
since it was safe for current users. Since we may be expanding
usage of printk_sched(), disable preepmtion for this function
to make it more generally safe to call.

Cc: Jan Kara <jack@...e.cz>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Jiri Bohac <jbohac@...e.cz>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 kernel/printk/printk.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 82d19e6..57467df 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2589,12 +2589,14 @@ int printk_sched(const char *fmt, ...)
 	va_list args;
 	int r;
 
+	preempt_disable();
 	va_start(args, fmt);
 	r = vprintk_emit(0, SCHED_MESSAGE_LOGLEVEL, NULL, 0, fmt, args);
 	va_end(args);
 
 	__this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
 	irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
+	preempt_enable();
 
 	return r;
 }
-- 
1.9.1

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