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authorRobert Richter <robert.richter@amd.com>2011-06-01 15:31:44 +0200
committerRobert Richter <robert.richter@amd.com>2011-06-15 14:31:29 +0200
commit8fe7e94eb71430cf63a742f3c19739d82a662758 (patch)
treedb624be62586a59c5f3954bf7c8c9188fa58d819
parent2c53b436a30867eb6b47dd7bab23ba638d1fb0d2 (diff)
downloadop-kernel-dev-8fe7e94eb71430cf63a742f3c19739d82a662758.zip
op-kernel-dev-8fe7e94eb71430cf63a742f3c19739d82a662758.tar.gz
oprofile, x86: Fix race in nmi handler while starting counters
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.suthikulpanit@amd.com> Cc: <stable@kernel.org> # .35+ Signed-off-by: Robert Richter <robert.richter@amd.com>
-rw-r--r--arch/x86/oprofile/nmi_int.c14
1 files changed, 10 insertions, 4 deletions
diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c
index cf97500..68894fd 100644
--- 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);
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