From: Masami Hiramatsu <mhiramat@redhat.com>
Date: Thu, 4 Mar 2010 03:38:50 +0000 (-0500)
Subject: x86: Issue at least one memory barrier in stop_machine_text_poke()
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=e5a11016643d1ab7172193591506d33a844734cc;p=deliverable%2Flinux.git

x86: Issue at least one memory barrier in stop_machine_text_poke()

Fix stop_machine_text_poke() to issue smp_mb() before exiting
waiting loop, and use cpu_relax() for waiting.

Changes in v2:
 - Don't use ACCESS_ONCE().

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Jason Baron <jbaron@redhat.com>
LKML-Reference: <20100304033850.3819.74590.stgit@localhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index c41f13c15e8f..e0b877099470 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -595,8 +595,8 @@ static int __kprobes stop_machine_text_poke(void *data)
 		wrote_text = 1;
 	} else {
 		while (!wrote_text)
-			smp_rmb();
-		sync_core();
+			cpu_relax();
+		smp_mb();	/* Load wrote_text before following execution */
 	}
 
 	flush_icache_range((unsigned long)tpp->addr,