linux-kernel - [PATCH] panic, vt: do not force oops output when panic

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Message-ID: <20110622223039.GA13916@google.com>
Date:	Wed, 22 Jun 2011 15:30:39 -0700
From:	Mandeep Singh Baines <msb@...omium.org>
To:	Mandeep Singh Baines <msb@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Huang Ying <ying.huang@...el.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Hugh Dickins <hughd@...omium.org>,
	Olaf Hering <olaf@...fle.de>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Dave Airlie <airlied@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] panic, vt: do not force oops output when panic_timeout < 0

Mandeep Singh Baines (msb@...omium.org) wrote:
> Avoid risk (of screen_unblank) and wasted cycles unblanking if
> you intend to reboot immediately.
> 

The original patch doesn't work. It worked fine when I tested with
a serial port. When I disabled the serial out, my machine started to
get wedged on a panic. I guess screen_unblank was in bust_spinlocks
for a reason. It probably bust some spin_locks somewhere.

Below is a replacement for this patch which calls screen_unblank but
does not force output when the panic timeout is negative (no wait).

-- >8 -- (snip)

Don't force output if you intend to reboot immediately.

This patch depends on:

http://lkml.kernel.org/r/1308612129-12488-1-git-send-email-msb@chromium.org

Change-Id: I48f86746ac36d420b1b025197f50d5d56b873e9f
Signed-off-by: Mandeep Singh Baines <msb@...omium.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Huang Ying <ying.huang@...el.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Olaf Hering <olaf@...fle.de>
Cc: Jesse Barnes <jbarnes@...tuousgeek.org>
Cc: Dave Airlie <airlied@...il.com>
Cc: Greg Kroah-Hartman <gregkh@...e.de>
---
 include/linux/vt_kern.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/vt_kern.h b/include/linux/vt_kern.h
index 4d05e14..c2164fa 100644
--- a/include/linux/vt_kern.h
+++ b/include/linux/vt_kern.h
@@ -137,7 +137,7 @@ int vty_init(const struct file_operations *console_fops);
 
 static inline bool vt_force_oops_output(struct vc_data *vc)
 {
-	if (oops_in_progress && vc->vc_panic_force_write)
+	if (oops_in_progress && vc->vc_panic_force_write  && panic_timeout >= 0)
 		return true;
 	return false;
 }
-- 
1.7.3.1

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