linux-kernel - [PATCH -tip 3/4]Text Edit Lock

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Date:	Fri, 06 Mar 2009 10:37:22 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Ingo Molnar <mingo@...e.hu>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH -tip 3/4]Text Edit Lock - Smp alternatives support

Use the mutual exclusion provided by the text edit lock in alternatives code.
Since alternative_smp_* will be called from module init code, etc,
we'd better protect it from other subsystems.

Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc: Ingo Molnar <mingo@...e.hu>
---
 arch/x86/kernel/alternative.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: 2.6.29-rc7/arch/x86/kernel/alternative.c
===================================================================
--- 2.6.29-rc7.orig/arch/x86/kernel/alternative.c
+++ 2.6.29-rc7/arch/x86/kernel/alternative.c
@@ -5,6 +5,7 @@
 #include <linux/kprobes.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
+#include <linux/memory.h>
 #include <asm/alternative.h>
 #include <asm/sections.h>
 #include <asm/pgtable.h>
@@ -226,6 +227,7 @@ static void alternatives_smp_lock(u8 **s
 {
 	u8 **ptr;

+	mutex_lock(&text_mutex);
 	for (ptr = start; ptr < end; ptr++) {
 		if (*ptr < text)
 			continue;
@@ -234,6 +236,7 @@ static void alternatives_smp_lock(u8 **s
 		/* turn DS segment override prefix into lock prefix */
 		text_poke(*ptr, ((unsigned char []){0xf0}), 1);
 	};
+	mutex_unlock(&text_mutex);
 }

 static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end)
@@ -243,6 +246,7 @@ static void alternatives_smp_unlock(u8 *
 	if (noreplace_smp)
 		return;

+	mutex_lock(&text_mutex);
 	for (ptr = start; ptr < end; ptr++) {
 		if (*ptr < text)
 			continue;
@@ -251,6 +255,7 @@ static void alternatives_smp_unlock(u8 *
 		/* turn lock prefix into DS segment override prefix */
 		text_poke(*ptr, ((unsigned char []){0x3E}), 1);
 	};
+	mutex_unlock(&text_mutex);
 }

 struct smp_alt_module {
-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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