linux-kernel - [PATCH] [9/23] PRINTK: Use stable variable to dump kmsg buffer

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Message-Id: <20100610111045.13CE3B1A2B@basil.firstfloor.org>
Date:	Thu, 10 Jun 2010 13:10:45 +0200 (CEST)
From:	Andi Kleen <andi@...stfloor.org>
To:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH] [9/23] PRINTK: Use stable variable to dump kmsg buffer


kmsg_dump takes care to sample the global variables
inside a spinlock, but then goes on to use the same
variables outside the spinlock region too.

Use the correct variable. This will make the race
window smaller.

Found by gcc 4.6's new warnings.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>

---
 kernel/printk.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Index: linux-2.6.35-rc2-gcc/kernel/printk.c
===================================================================
--- linux-2.6.35-rc2-gcc.orig/kernel/printk.c
+++ linux-2.6.35-rc2-gcc/kernel/printk.c
@@ -1520,9 +1520,9 @@ void kmsg_dump(enum kmsg_dump_reason rea
 	chars = logged_chars;
 	spin_unlock_irqrestore(&logbuf_lock, flags);
 
-	if (logged_chars > end) {
-		s1 = log_buf + log_buf_len - logged_chars + end;
-		l1 = logged_chars - end;
+	if (chars > end) {
+		s1 = log_buf + log_buf_len - chars + end;
+		l1 = chars - end;
 
 		s2 = log_buf;
 		l2 = end;
@@ -1530,8 +1530,8 @@ void kmsg_dump(enum kmsg_dump_reason rea
 		s1 = "";
 		l1 = 0;
 
-		s2 = log_buf + end - logged_chars;
-		l2 = logged_chars;
+		s2 = log_buf + end - chars;
+		l2 = chars;
 	}
 
 	if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
--
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