linux-kernel - [PATCH 1/2] [RESEND] console: use might_sleep in console

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Date:	Tue, 18 Sep 2012 01:03:31 +0200
From:	Daniel Vetter <daniel.vetter@...ll.ch>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
	DRI Development <dri-devel@...ts.freedesktop.org>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Dave Airlie <airlied@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [PATCH 1/2] [RESEND] console: use might_sleep in console_lock

Instead of BUG_ON(in_interrupt()), since that doesn't check for all
the newfangled stuff like preempt.

Note that this is valid since the console_sem is essentially used like
a real mutex with only two twists:
- we allow trylock from hardirq context
- across suspend/resume we lock the logical console_lock, but drop the
  semaphore protecting the locking state.

Now that doesn't guarantee that no one is playing tricks in
single-thread atomic contexts at suspend/resume/boot time, but
- I couldn't find anything suspicious with some grepping,
- might_sleep shouldn't die,
- and I think the upside of catching more potential issues is worth
  the risk of getting a might_sleep backtrace that would have been
  save (and then dealing with that fallout).

Cc: Dave Airlie <airlied@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
---
 kernel/printk.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/printk.c b/kernel/printk.c
index 66a2ea3..ed9af6a 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1909,7 +1909,8 @@ static int __cpuinit console_cpu_notify(struct notifier_block *self,
  */
 void console_lock(void)
 {
-	BUG_ON(in_interrupt());
+	might_sleep();
+
 	down(&console_sem);
 	if (console_suspended)
 		return;
-- 
1.7.10.4

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