x86, mce: make polling timer interval per CPU

The polling timer while running per CPU still uses a global next_interval
variable, which lead to some CPUs either polling too fast or too slow.   
This was not a serious problem because all errors get picked up eventually,
but it's still better to avoid it. Turn next_interval into a per cpu variable.

v2: Fix check_interval == 0 case (Hidetoshi Seto)

[ Impact: minor bug fix ]

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 12 insertions, 12 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce_64.c b/arch/x86/kernel/cpu/mcheck/mce_64.c
index 863f89568b1a..82614f1b923a 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_64.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_64.c
@@ -452,13 +452,14 @@ void mce_log_therm_throt_event(__u64 status)
  */
 
 static int check_interval = 5 * 60; /* 5 minutes */
-static int next_interval; /* in jiffies */
+static DEFINE_PER_CPU(int, next_interval); /* in jiffies */
 static void mcheck_timer(unsigned long);
 static DEFINE_PER_CPU(struct timer_list, mce_timer);
 
 static void mcheck_timer(unsigned long data)
 {
         struct timer_list *t = &per_cpu(mce_timer, data);
+        int *n;
 
         WARN_ON(smp_processor_id() != data);
 
@@ -470,14 +471,14 @@ static void mcheck_timer(unsigned long data)
          * Alert userspace if needed.  If we logged an MCE, reduce the
          * polling interval, otherwise increase the polling interval.
          */
+        n = &__get_cpu_var(next_interval);
         if (mce_notify_user()) {
-                next_interval = max(next_interval/2, HZ/100);
+                *n = max(*n/2, HZ/100);
         } else {
-                next_interval = min(next_interval * 2,
-                                (int)round_jiffies_relative(check_interval*HZ));
+                *n = min(*n*2, (int)round_jiffies_relative(check_interval*HZ));
         }
 
-        t->expires = jiffies + next_interval;
+        t->expires = jiffies + *n;
         add_timer(t);
 }
 
@@ -632,14 +633,13 @@ static void mce_cpu_features(struct cpuinfo_x86 *c)
 static void mce_init_timer(void)
 {
         struct timer_list *t = &__get_cpu_var(mce_timer);
+        int *n = &__get_cpu_var(next_interval);
 
-        /* data race harmless because everyone sets to the same value */
-        if (!next_interval)
-                next_interval = check_interval * HZ;
-        if (!next_interval)
+        *n = check_interval * HZ;
+        if (!*n)
                 return;
         setup_timer(t, mcheck_timer, smp_processor_id());
-        t->expires = round_jiffies(jiffies + next_interval);
+        t->expires = round_jiffies(jiffies + *n);
         add_timer(t);
 }
 
@@ -907,7 +907,6 @@ static void mce_cpu_restart(void *data)
 /* Reinit MCEs after user configuration changes */
 static void mce_restart(void)
 {
-        next_interval = check_interval * HZ;
         on_each_cpu(mce_cpu_restart, NULL, 1);
 }
 
@@ -1110,7 +1109,8 @@ static int __cpuinit mce_cpu_callback(struct notifier_block *nfb,
                 break;
         case CPU_DOWN_FAILED:
         case CPU_DOWN_FAILED_FROZEN:
-                t->expires = round_jiffies(jiffies + next_interval);
+                t->expires = round_jiffies(jiffies +
+                                                __get_cpu_var(next_interval));
                 add_timer_on(t, cpu);
                 smp_call_function_single(cpu, mce_reenable_cpu, &action, 1);
                 break;