linux-kernel - [PATCH v7 2/2] x86 mce: use new printk recursion disabling interface

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Date:	Thu, 07 Jun 2012 11:00:03 +0800
From:	ShuoX Liu <shuox.liu@...el.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	Borislav Petkov <bp@...en8.de>,
	Yanmin Zhang <yanmin_zhang@...ux.intel.com>,
	"Luck, Tony" <tony.luck@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: [PATCH v7 2/2] x86 mce: use new printk recursion disabling interface

From: ShuoX Liu <shuox.liu@...el.com>

On x86 machines, some times MCE happens just when kernel calls printk
to output some log info to serial console, while usually MCE module in
kernel is used to print out some hardware error information, such like
bad cache or bad memory bank. That causes printk recursion and printk
would omit MCE printk output.

We hit it when running MTBF testing on Android ATOM mobiles.

Here in print_mce, we choose to disable printk recursion to make sure
MCE logs printed out.

Signed-off-by: Yanmin Zhang <yanmin_zhang@...ux.intel.com>
Signed-off-by: ShuoX Liu <shuox.liu@...el.com>
---
 arch/x86/kernel/cpu/mcheck/mce.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 2afcbd2..6056e94 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -242,6 +242,7 @@ static void print_mce(struct mce *m)
 {
 	int ret = 0;
 
+	printk_recursion_check_disable();
 	pr_emerg(HW_ERR "CPU %d: Machine Check Exception: %Lx Bank %d: %016Lx\n",
 	       m->extcpu, m->mcgstatus, m->bank, m->status);
 
@@ -275,10 +276,13 @@ static void print_mce(struct mce *m)
 	 * (if the CPU has an implementation for that)
 	 */
 	ret = atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, m);
-	if (ret == NOTIFY_STOP)
+	if (ret == NOTIFY_STOP) {
+		printk_recursion_check_enable();
 		return;
+	}
 
 	pr_emerg_ratelimited(HW_ERR "Run the above through 'mcelog --ascii'\n");
+	printk_recursion_check_enable();
 }
 
 #define PANIC_TIMEOUT 5 /* 5 seconds */
-- 
1.7.1

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