linux-kernel - [PATCH] printk: ignore recursion

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Date:	Wed, 23 May 2012 09:58:34 +0800
From:	ShuoX Liu <shuox.liu@...el.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	andi@...stfloor.org, Andrew Morton <akpm@...ux-foundation.org>,
	Yanmin Zhang <yanmin_zhang@...ux.intel.com>
Subject: [PATCH] printk: ignore recursion_bug flag when MCE in progress

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

When MCE happens in printk, we ignore recursion_bug to make sure
some MCE logs printed out. Re-use mce_entry variable.

Signed-off-by: Yanmin Zhang <yanmin_zhang@...ux.intel.com>
Signed-off-by: ShuoX Liu <shuox.liu@...el.com>
---
I found mce_entry was introduced by commit 553f265f, but it's not
used now. Why not removed?
---
 arch/x86/include/asm/mce.h       |    2 --
 arch/x86/kernel/cpu/mcheck/mce.c |    2 --
 include/linux/kernel.h           |    1 +
 kernel/printk.c                  |    4 +++-
 4 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 441520e..aeda4cc 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -187,8 +187,6 @@ int mce_available(struct cpuinfo_x86 *c);
 DECLARE_PER_CPU(unsigned, mce_exception_count);
 DECLARE_PER_CPU(unsigned, mce_poll_count);
 
-extern atomic_t mce_entry;
-
 typedef DECLARE_BITMAP(mce_banks_t, MAX_NR_BANKS);
 DECLARE_PER_CPU(mce_banks_t, mce_poll_banks);
 
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 11c9166..6073354 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -61,8 +61,6 @@ int mce_disabled __read_mostly;
 
 #define SPINUNIT 100	/* 100ns */
 
-atomic_t mce_entry;
-
 DEFINE_PER_CPU(unsigned, mce_exception_count);
 
 /*
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 645231c..24af685 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -354,6 +354,7 @@ unsigned long int_sqrt(unsigned long);
 extern void bust_spinlocks(int yes);
 extern void wake_up_klogd(void);
 extern int oops_in_progress;		/* If set, an oops, panic(), BUG() or die() is in progress */
+extern atomic_t mce_entry;
 extern int panic_timeout;
 extern int panic_on_oops;
 extern int panic_on_unrecovered_nmi;
diff --git a/kernel/printk.c b/kernel/printk.c
index 473afdb..2bae087 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -79,6 +79,7 @@ int console_printk[4] = {
 int oops_in_progress;
 EXPORT_SYMBOL(oops_in_progress);
 
+atomic_t mce_entry;
 /*
  * console_sem protects the console_drivers list, and also
  * provides serialisation for access to the entire console
@@ -864,7 +865,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 		 * recursion and return - but flag the recursion so that
 		 * it can be printed at the next appropriate moment:
 		 */
-		if (!oops_in_progress && !lockdep_recursing(current)) {
+		if (!oops_in_progress && !atomic_read(&mce_entry)
+				&& !lockdep_recursing(current)) {
 			recursion_bug = 1;
 			goto out_restore_irqs;
 		}
-- 
1.7.1
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