[PATCH -tip 2/2] x86: Issue at least one memory barrier in stop_machine_text_poke().

[Masami Hiramatsu]

Fix stop_machine_text_poke() to issue smp_mb() before exiting waiting
loop. Also, use ACCESS_ONCE() to check a flag according to Mathieu's
comment.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jason Baron <jbaron@redhat.com>
---

 arch/x86/kernel/alternative.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 635e4f4..3236a11 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -596,9 +596,9 @@ static int __kprobes stop_machine_text_poke(void *data)
 		smp_wmb();	/* Make sure other cpus see that this has run */
 		wrote_text = 1;
 	} else {
-		while (!wrote_text)
-			smp_rmb();
-		sync_core();
+		while (!ACCESS_ONCE(wrote_text))
+			cpu_relax();
+		smp_mb();	/* Load wrote_text before following execution */
 	}
 
 	flush_icache_range((unsigned long)tpp->addr,


-- 
Masami Hiramatsu

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

e-mail: mhiramat@redhat.com