This is a note to let you know that I've just added the patch titled
oprofile, x86: Fix race in nmi handler while starting
to the 2.6.39-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
oprofile-x86-fix-race-in-nmi-handler-while-starting.patch
and it can be found in the queue-2.6.39 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <sta...@kernel.org> know about it.
>From 8fe7e94eb71430cf63a742f3c19739d82a662758 Mon Sep 17 00:00:00 2001
From: Robert Richter <robert.rich...@amd.com>
Date: Wed, 1 Jun 2011 15:31:44 +0200
Subject: oprofile, x86: Fix race in nmi handler while starting
counters
From: Robert Richter <robert.rich...@amd.com>
commit 8fe7e94eb71430cf63a742f3c19739d82a662758 upstream.
In some rare cases, nmis are generated immediately after the nmi
handler of the cpu was started. This causes the counter not to be
enabled. Before enabling the nmi handlers we need to set variable
ctr_running first and make sure its value is written to memory.
Also, the patch makes all existing barriers a memory barrier instead
of a compiler barrier only.
Reported-by: Suravee Suthikulpanit <suravee.suthikulpa...@amd.com>
Signed-off-by: Robert Richter <robert.rich...@amd.com>
Signed-off-by: Greg Kroah-Hartman <gre...@suse.de>
---
arch/x86/oprofile/nmi_int.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
--- a/arch/x86/oprofile/nmi_int.c
+++ b/arch/x86/oprofile/nmi_int.c
@@ -112,8 +112,10 @@ static void nmi_cpu_start(void *dummy)
static int nmi_start(void)
{
get_online_cpus();
- on_each_cpu(nmi_cpu_start, NULL, 1);
ctr_running = 1;
+ /* make ctr_running visible to the nmi handler: */
+ smp_mb();
+ on_each_cpu(nmi_cpu_start, NULL, 1);
put_online_cpus();
return 0;
}
@@ -504,15 +506,18 @@ static int nmi_setup(void)
nmi_enabled = 0;
ctr_running = 0;
- barrier();
+ /* make variables visible to the nmi handler: */
+ smp_mb();
err = register_die_notifier(&profile_exceptions_nb);
if (err)
goto fail;
get_online_cpus();
register_cpu_notifier(&oprofile_cpu_nb);
- on_each_cpu(nmi_cpu_setup, NULL, 1);
nmi_enabled = 1;
+ /* make nmi_enabled visible to the nmi handler: */
+ smp_mb();
+ on_each_cpu(nmi_cpu_setup, NULL, 1);
put_online_cpus();
return 0;
@@ -531,7 +536,8 @@ static void nmi_shutdown(void)
nmi_enabled = 0;
ctr_running = 0;
put_online_cpus();
- barrier();
+ /* make variables visible to the nmi handler: */
+ smp_mb();
unregister_die_notifier(&profile_exceptions_nb);
msrs = &get_cpu_var(cpu_msrs);
model->shutdown(msrs);
Patches currently in stable-queue which might be from robert.rich...@amd.com are
queue-2.6.39/oprofile-x86-fix-race-in-nmi-handler-while-starting.patch
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