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authorRobert Richter <robert.richter@amd.com>2011-06-01 09:31:44 -0400
committerRobert Richter <robert.richter@amd.com>2011-06-15 08:31:29 -0400
commit8fe7e94eb71430cf63a742f3c19739d82a662758 (patch)
treedb624be62586a59c5f3954bf7c8c9188fa58d819 /arch/x86
parent2c53b436a30867eb6b47dd7bab23ba638d1fb0d2 (diff)
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>
Diffstat (limited to 'arch/x86')
-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 cf9750004a08..68894fdc034b 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)
112static int nmi_start(void) 112static int nmi_start(void)
113{ 113{
114 get_online_cpus(); 114 get_online_cpus();
115 on_each_cpu(nmi_cpu_start, NULL, 1);
116 ctr_running = 1; 115 ctr_running = 1;
116 /* make ctr_running visible to the nmi handler: */
117 smp_mb();
118 on_each_cpu(nmi_cpu_start, NULL, 1);
117 put_online_cpus(); 119 put_online_cpus();
118 return 0; 120 return 0;
119} 121}
@@ -504,15 +506,18 @@ static int nmi_setup(void)
504 506
505 nmi_enabled = 0; 507 nmi_enabled = 0;
506 ctr_running = 0; 508 ctr_running = 0;
507 barrier(); 509 /* make variables visible to the nmi handler: */
510 smp_mb();
508 err = register_die_notifier(&profile_exceptions_nb); 511 err = register_die_notifier(&profile_exceptions_nb);
509 if (err) 512 if (err)
510 goto fail; 513 goto fail;
511 514
512 get_online_cpus(); 515 get_online_cpus();
513 register_cpu_notifier(&oprofile_cpu_nb); 516 register_cpu_notifier(&oprofile_cpu_nb);
514 on_each_cpu(nmi_cpu_setup, NULL, 1);
515 nmi_enabled = 1; 517 nmi_enabled = 1;
518 /* make nmi_enabled visible to the nmi handler: */
519 smp_mb();
520 on_each_cpu(nmi_cpu_setup, NULL, 1);
516 put_online_cpus(); 521 put_online_cpus();
517 522
518 return 0; 523 return 0;
@@ -531,7 +536,8 @@ static void nmi_shutdown(void)
531 nmi_enabled = 0; 536 nmi_enabled = 0;
532 ctr_running = 0; 537 ctr_running = 0;
533 put_online_cpus(); 538 put_online_cpus();
534 barrier(); 539 /* make variables visible to the nmi handler: */
540 smp_mb();
535 unregister_die_notifier(&profile_exceptions_nb); 541 unregister_die_notifier(&profile_exceptions_nb);
536 msrs = &get_cpu_var(cpu_msrs); 542 msrs = &get_cpu_var(cpu_msrs);
537 model->shutdown(msrs); 543 model->shutdown(msrs);