linux-kernel - [RFC][PATCH v3 3/3]skip subsequent kmsg

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Date:	Fri, 2 Dec 2011 17:12:43 -0500
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	Don Zickus <dzickus@...hat.com>,
	Matthew Garrett <mjg@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	"Chen, Gong" <gong.chen@...el.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"'ying.huang@...el.com'" <'ying.huang@...el.com'>,
	"'ak@...ux.intel.com'" <'ak@...ux.intel.com'>,
	"'hughd@...omium.org'" <'hughd@...omium.org'>,
	"'mingo@...e.hu'" <'mingo@...e.hu'>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"namhyung@...il.com" <namhyung@...il.com>
CC:	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: [RFC][PATCH v3 3/3]skip subsequent kmsg_dump() function calls in
 panic path

This patch skips subsequent kmsg_dump() function calls in panic path

With this patch, we can avoid deadlock due to the subsequent calls.
Actually, kmsg_dump(KMSG_DUMP_EMERG) is called after kmsg_dump(KMSG_DUMP_PANIC) 
when panic_timeout variable is set.

 Signed-off-by: Seiji Aguchi <seiji.aguchi@....com>

---
 kernel/printk.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/kernel/printk.c b/kernel/printk.c
index bc5ac61..25d6dc1 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1731,6 +1731,16 @@ void kmsg_dump(enum kmsg_dump_reason reason)
 	const char *s1, *s2;
 	unsigned long l1, l2;
 	unsigned long flags;
+	static bool panicked;
+
+	/*
+	 * kmsg_dump() is skipped because we already got panic log.
+	 */
+	if (panicked)
+		return;
+
+	if (reason == KMSG_DUMP_PANIC)
+		panicked = true;
 
 	WARN_ON(in_nmi() && reason != KMSG_DUMP_PANIC);
 
-- 
1.7.1


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