[PATCH] [1/4] x86: MCE: Make polling timer interval per CPU v2

Andi Kleen
2009-04-09T10:28:58Z

This v2 version fixes the check_interval == 0 case noticed by Seto-san.
Please apply.

-Andi

---

x86: MCE: Make polling timer interval per CPU v2

Impact: bug fix

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)

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
arch/x86/kernel/cpu/mcheck/mce_64.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)

Index: linux/arch/x86/kernel/cpu/mcheck/mce_64.c
===================================================================
--- linux.orig/arch/x86/kernel/cpu/mcheck/mce_64.c 2009-04-09 11:43:58.000000000 +0200
+++ linux/arch/x86/kernel/cpu/mcheck/mce_64.c 2009-04-09 12:16:33.000000000 +0200
@@ -452,13 +452,14 @@
*/

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 @@
* 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_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 @@
/* 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 @@
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;