2009-10-07 23:13:37

by Christoph Lameter

Subject: [Patch vs. percpu-next] Use this_cpu_xx in nmi handling

From: Christoph Lameter <[email protected]>
Subject: Use this_cpu_xx in nmi handling

this_cpu_inc/dec reduces the number of instructions needed.

Signed-off-by: Christoph Lameter <[email protected]>


---
arch/sparc/kernel/nmi.c | 8 ++++----
arch/x86/kernel/apic/nmi.c | 8 ++++----
2 files changed, 8 insertions(+), 8 deletions(-)

Index: linux-2.6/arch/sparc/kernel/nmi.c
===================================================================
--- linux-2.6.orig/arch/sparc/kernel/nmi.c 2009-10-07 16:58:11.000000000 -0500
+++ linux-2.6/arch/sparc/kernel/nmi.c 2009-10-07 17:12:35.000000000 -0500
@@ -47,7 +47,7 @@ static DEFINE_PER_CPU(short, wd_enabled)
static int endflag __initdata;

static DEFINE_PER_CPU(unsigned int, last_irq_sum);
-static DEFINE_PER_CPU(local_t, alert_counter);
+static DEFINE_PER_CPU(long, alert_counter);
static DEFINE_PER_CPU(int, nmi_touch);

void touch_nmi_watchdog(void)
@@ -112,13 +112,13 @@ notrace __kprobes void perfctr_irq(int i
touched = 1;
}
if (!touched && __get_cpu_var(last_irq_sum) == sum) {
- local_inc(&__get_cpu_var(alert_counter));
- if (local_read(&__get_cpu_var(alert_counter)) == 30 * nmi_hz)
+ __this_cpu_inc(per_cpu_var(alert_counter));
+ if (__this_cpu_read(per_cpu_var(alert_counter)) == 30 * nmi_hz)
die_nmi("BUG: NMI Watchdog detected LOCKUP",
regs, panic_on_timeout);
} else {
__get_cpu_var(last_irq_sum) = sum;
- local_set(&__get_cpu_var(alert_counter), 0);
+ __this_cpu_write(per_cpu_var(alert_counter), 0);
}
if (__get_cpu_var(wd_enabled)) {
write_pic(picl_value(nmi_hz));
Index: linux-2.6/arch/x86/kernel/apic/nmi.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/nmi.c 2009-10-07 16:56:39.000000000 -0500
+++ linux-2.6/arch/x86/kernel/apic/nmi.c 2009-10-07 16:58:02.000000000 -0500
@@ -360,7 +360,7 @@ void stop_apic_nmi_watchdog(void *unused
*/

static DEFINE_PER_CPU(unsigned, last_irq_sum);
-static DEFINE_PER_CPU(local_t, alert_counter);
+static DEFINE_PER_CPU(long, alert_counter);
static DEFINE_PER_CPU(int, nmi_touch);

void touch_nmi_watchdog(void)
@@ -437,8 +437,8 @@ nmi_watchdog_tick(struct pt_regs *regs,
* Ayiee, looks like this CPU is stuck ...
* wait a few IRQs (5 seconds) before doing the oops ...
*/
- local_inc(&__get_cpu_var(alert_counter));
- if (local_read(&__get_cpu_var(alert_counter)) == 5 * nmi_hz)
+ __this_cpu_inc(per_cpu_var(alert_counter));
+ if (__this_cpu_read(per_cpu_var(alert_counter)) == 5 * nmi_hz)
/*
* die_nmi will return ONLY if NOTIFY_STOP happens..
*/
@@ -446,7 +446,7 @@ nmi_watchdog_tick(struct pt_regs *regs,
regs, panic_on_timeout);
} else {
__get_cpu_var(last_irq_sum) = sum;
- local_set(&__get_cpu_var(alert_counter), 0);
+ __this_cpu_write(per_cpu_var(alert_counter), 0);
}

/* see if the nmi watchdog went off */

2009-10-12 10:53:34

by Tejun Heo

Subject: Re: [Patch vs. percpu-next] Use this_cpu_xx in nmi handling

Christoph Lameter wrote:
> From: Christoph Lameter <[email protected]>
> Subject: Use this_cpu_xx in nmi handling
>
> this_cpu_inc/dec reduces the number of instructions needed.
>
> Signed-off-by: Christoph Lameter <[email protected]>

applied to percpu#for-next.

Thanks.

--
tejun