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[PATCH -tip 2/2] x86: Issue at least one memory barrier in stop_machine_text_poke().
- From: Masami Hiramatsu <mhiramat at redhat dot com>
- To: Ingo Molnar <mingo at elte dot hu>, lkml<linux-kernel at vger dot kernel dot org>
- Cc: systemtap<systemtap at sources dot redhat dot com>, DLE<dle-develop at lists dot sourceforge dot net>, Masami Hiramatsu <mhiramat at redhat dot com>, Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>, Ingo Molnar <mingo at elte dot hu>, Jason Baron <jbaron at redhat dot com>
- Date: Wed, 03 Mar 2010 16:27:04 -0500
- Subject: [PATCH -tip 2/2] x86: Issue at least one memory barrier in stop_machine_text_poke().
- References: <20100303212656.25645.48466.stgit@localhost6.localdomain6>
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