Commit-ID: 8fe7e94eb71430cf63a742f3c19739d82a662758
Gitweb: http://git.kernel.org/tip/8fe7e94eb71430cf63a742f3c19739d82a662758
Author: Robert Richter <robert.richter@xxxxxxx>
AuthorDate: Wed, 1 Jun 2011 15:31:44 +0200
Committer: Robert Richter <robert.richter@xxxxxxx>
CommitDate: Wed, 15 Jun 2011 14:31:29 +0200
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@xxxxxxx>
Cc: <stable@xxxxxxxxxx> # .35+
Signed-off-by: Robert Richter <robert.richter@xxxxxxx>
---
arch/x86/oprofile/nmi_int.c | 14 ++++++++++----
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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