494fc42170
__get_cpu_var() is used for multiple purposes in the kernel source. One of
them is address calculation via the form &__get_cpu_var(x). This calculates
the address for the instance of the percpu variable of the current processor
based on an offset.
Other use cases are for storing and retrieving data from the current
processors percpu area. __get_cpu_var() can be used as an lvalue when
writing data or on the right side of an assignment.
__get_cpu_var() is defined as :
#define __get_cpu_var(var) (*this_cpu_ptr(&(var)))
__get_cpu_var() always only does an address determination. However, store
and retrieve operations could use a segment prefix (or global register on
other platforms) to avoid the address calculation.
this_cpu_write() and this_cpu_read() can directly take an offset into a
percpu area and use optimized assembly code to read and write per cpu
variables.
This patch converts __get_cpu_var into either an explicit address
calculation using this_cpu_ptr() or into a use of this_cpu operations that
use the offset. Thereby address calculations are avoided and less registers
are used when code is generated.
At the end of the patch set all uses of __get_cpu_var have been removed so
the macro is removed too.
The patch set includes passes over all arches as well. Once these operations
are used throughout then specialized macros can be defined in non -x86
arches as well in order to optimize per cpu access by f.e. using a global
register that may be set to the per cpu base.
Transformations done to __get_cpu_var()
1. Determine the address of the percpu instance of the current processor.
DEFINE_PER_CPU(int, y);
int *x = &__get_cpu_var(y);
Converts to
int *x = this_cpu_ptr(&y);
2. Same as #1 but this time an array structure is involved.
DEFINE_PER_CPU(int, y[20]);
int *x = __get_cpu_var(y);
Converts to
int *x = this_cpu_ptr(y);
3. Retrieve the content of the current processors instance of a per cpu
variable.
DEFINE_PER_CPU(int, y);
int x = __get_cpu_var(y)
Converts to
int x = __this_cpu_read(y);
4. Retrieve the content of a percpu struct
DEFINE_PER_CPU(struct mystruct, y);
struct mystruct x = __get_cpu_var(y);
Converts to
memcpy(&x, this_cpu_ptr(&y), sizeof(x));
5. Assignment to a per cpu variable
DEFINE_PER_CPU(int, y)
__get_cpu_var(y) = x;
Converts to
__this_cpu_write(y, x);
6. Increment/Decrement etc of a per cpu variable
DEFINE_PER_CPU(int, y);
__get_cpu_var(y)++
Converts to
__this_cpu_inc(y)
Cc: sparclinux@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
273 lines
6 KiB
C
273 lines
6 KiB
C
/* Pseudo NMI support on sparc64 systems.
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*
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* Copyright (C) 2009 David S. Miller <davem@davemloft.net>
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*
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* The NMI watchdog support and infrastructure is based almost
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* entirely upon the x86 NMI support code.
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*/
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#include <linux/kernel.h>
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#include <linux/param.h>
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#include <linux/init.h>
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#include <linux/percpu.h>
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#include <linux/nmi.h>
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#include <linux/export.h>
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#include <linux/kprobes.h>
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#include <linux/kernel_stat.h>
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#include <linux/reboot.h>
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#include <linux/slab.h>
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#include <linux/kdebug.h>
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#include <linux/delay.h>
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#include <linux/smp.h>
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#include <asm/perf_event.h>
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#include <asm/ptrace.h>
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#include <asm/pcr.h>
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#include "kstack.h"
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/* We don't have a real NMI on sparc64, but we can fake one
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* up using profiling counter overflow interrupts and interrupt
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* levels.
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*
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* The profile overflow interrupts at level 15, so we use
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* level 14 as our IRQ off level.
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*/
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static int panic_on_timeout;
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/* nmi_active:
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* >0: the NMI watchdog is active, but can be disabled
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* <0: the NMI watchdog has not been set up, and cannot be enabled
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* 0: the NMI watchdog is disabled, but can be enabled
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*/
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atomic_t nmi_active = ATOMIC_INIT(0); /* oprofile uses this */
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EXPORT_SYMBOL(nmi_active);
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static unsigned int nmi_hz = HZ;
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static DEFINE_PER_CPU(short, wd_enabled);
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static int endflag __initdata;
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static DEFINE_PER_CPU(unsigned int, last_irq_sum);
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static DEFINE_PER_CPU(long, alert_counter);
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static DEFINE_PER_CPU(int, nmi_touch);
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void touch_nmi_watchdog(void)
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{
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if (atomic_read(&nmi_active)) {
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int cpu;
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for_each_present_cpu(cpu) {
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if (per_cpu(nmi_touch, cpu) != 1)
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per_cpu(nmi_touch, cpu) = 1;
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}
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}
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touch_softlockup_watchdog();
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}
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EXPORT_SYMBOL(touch_nmi_watchdog);
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static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
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{
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int this_cpu = smp_processor_id();
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if (notify_die(DIE_NMIWATCHDOG, str, regs, 0,
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pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
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return;
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if (do_panic || panic_on_oops)
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panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
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else
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WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
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}
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notrace __kprobes void perfctr_irq(int irq, struct pt_regs *regs)
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{
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unsigned int sum, touched = 0;
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void *orig_sp;
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clear_softint(1 << irq);
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local_cpu_data().__nmi_count++;
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nmi_enter();
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orig_sp = set_hardirq_stack();
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if (notify_die(DIE_NMI, "nmi", regs, 0,
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pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
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touched = 1;
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else
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pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
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sum = local_cpu_data().irq0_irqs;
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if (__this_cpu_read(nmi_touch)) {
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__this_cpu_write(nmi_touch, 0);
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touched = 1;
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}
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if (!touched && __this_cpu_read(last_irq_sum) == sum) {
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__this_cpu_inc(alert_counter);
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if (__this_cpu_read(alert_counter) == 30 * nmi_hz)
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die_nmi("BUG: NMI Watchdog detected LOCKUP",
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regs, panic_on_timeout);
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} else {
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__this_cpu_write(last_irq_sum, sum);
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__this_cpu_write(alert_counter, 0);
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}
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if (__this_cpu_read(wd_enabled)) {
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pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
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pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
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}
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restore_hardirq_stack(orig_sp);
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nmi_exit();
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}
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static inline unsigned int get_nmi_count(int cpu)
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{
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return cpu_data(cpu).__nmi_count;
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}
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static __init void nmi_cpu_busy(void *data)
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{
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while (endflag == 0)
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mb();
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}
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static void report_broken_nmi(int cpu, int *prev_nmi_count)
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{
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printk(KERN_CONT "\n");
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printk(KERN_WARNING
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"WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
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cpu, prev_nmi_count[cpu], get_nmi_count(cpu));
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printk(KERN_WARNING
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"Please report this to bugzilla.kernel.org,\n");
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printk(KERN_WARNING
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"and attach the output of the 'dmesg' command.\n");
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per_cpu(wd_enabled, cpu) = 0;
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atomic_dec(&nmi_active);
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}
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void stop_nmi_watchdog(void *unused)
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{
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pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
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__this_cpu_write(wd_enabled, 0);
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atomic_dec(&nmi_active);
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}
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static int __init check_nmi_watchdog(void)
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{
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unsigned int *prev_nmi_count;
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int cpu, err;
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if (!atomic_read(&nmi_active))
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return 0;
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prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(unsigned int), GFP_KERNEL);
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if (!prev_nmi_count) {
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err = -ENOMEM;
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goto error;
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}
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printk(KERN_INFO "Testing NMI watchdog ... ");
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smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
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for_each_possible_cpu(cpu)
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prev_nmi_count[cpu] = get_nmi_count(cpu);
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local_irq_enable();
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mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
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for_each_online_cpu(cpu) {
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if (!per_cpu(wd_enabled, cpu))
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continue;
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if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
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report_broken_nmi(cpu, prev_nmi_count);
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}
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endflag = 1;
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if (!atomic_read(&nmi_active)) {
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kfree(prev_nmi_count);
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atomic_set(&nmi_active, -1);
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err = -ENODEV;
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goto error;
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}
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printk("OK.\n");
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nmi_hz = 1;
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kfree(prev_nmi_count);
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return 0;
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error:
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on_each_cpu(stop_nmi_watchdog, NULL, 1);
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return err;
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}
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void start_nmi_watchdog(void *unused)
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{
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__this_cpu_write(wd_enabled, 1);
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atomic_inc(&nmi_active);
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pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
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pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
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pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
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}
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static void nmi_adjust_hz_one(void *unused)
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{
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if (!__this_cpu_read(wd_enabled))
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return;
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pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
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pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
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pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
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}
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void nmi_adjust_hz(unsigned int new_hz)
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{
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nmi_hz = new_hz;
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on_each_cpu(nmi_adjust_hz_one, NULL, 1);
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}
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EXPORT_SYMBOL_GPL(nmi_adjust_hz);
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static int nmi_shutdown(struct notifier_block *nb, unsigned long cmd, void *p)
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{
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on_each_cpu(stop_nmi_watchdog, NULL, 1);
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return 0;
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}
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static struct notifier_block nmi_reboot_notifier = {
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.notifier_call = nmi_shutdown,
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};
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int __init nmi_init(void)
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{
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int err;
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on_each_cpu(start_nmi_watchdog, NULL, 1);
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err = check_nmi_watchdog();
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if (!err) {
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err = register_reboot_notifier(&nmi_reboot_notifier);
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if (err) {
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on_each_cpu(stop_nmi_watchdog, NULL, 1);
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atomic_set(&nmi_active, -1);
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}
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}
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return err;
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}
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static int __init setup_nmi_watchdog(char *str)
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{
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if (!strncmp(str, "panic", 5))
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panic_on_timeout = 1;
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return 0;
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}
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__setup("nmi_watchdog=", setup_nmi_watchdog);
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