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watchdog: store the watchdog sample period as a variable 

Currently getting the sample period is always thru a complex
calculation: get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5).

We can store the sample period as a variable, and set it as __read_mostly
type.

Signed-off-by: liu chuansheng <chuansheng.liu@intel.com>
Cc: Don Zickus <dzickus@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Chuansheng Liu 2012-12-17 15:59:50 -08:00 committed by Linus Torvalds
parent 2bf0a8f67f
commit 0f34c40091
1 changed files with 8 additions and 5 deletions
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13
kernel/watchdog.c
View File

@ -31,6 +31,7 @@
int watchdog_enabled = 1; int watchdog_enabled = 1;
int __read_mostly watchdog_thresh = 10; int __read_mostly watchdog_thresh = 10;
static int __read_mostly watchdog_disabled; static int __read_mostly watchdog_disabled;
static u64 __read_mostly sample_period;
static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
@ -116,7 +117,7 @@ static unsigned long get_timestamp(int this_cpu)
return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
} }
static u64 get_sample_period(void) static void set_sample_period(void)
{ {
/* /*
* convert watchdog_thresh from seconds to ns * convert watchdog_thresh from seconds to ns
@ -125,7 +126,7 @@ static u64 get_sample_period(void)
* and hard thresholds) to increment before the * and hard thresholds) to increment before the
* hardlockup detector generates a warning * hardlockup detector generates a warning
*/ */
return get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
} }
/* Commands for resetting the watchdog */ /* Commands for resetting the watchdog */
@ -275,7 +276,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
wake_up_process(__this_cpu_read(softlockup_watchdog)); wake_up_process(__this_cpu_read(softlockup_watchdog));
/* .. and repeat */ /* .. and repeat */
hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period())); hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
if (touch_ts == 0) { if (touch_ts == 0) {
if (unlikely(__this_cpu_read(softlockup_touch_sync))) { if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
@ -356,7 +357,7 @@ static void watchdog_enable(unsigned int cpu)
hrtimer->function = watchdog_timer_fn; hrtimer->function = watchdog_timer_fn;
/* done here because hrtimer_start can only pin to smp_processor_id() */ /* done here because hrtimer_start can only pin to smp_processor_id() */
hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()), hrtimer_start(hrtimer, ns_to_ktime(sample_period),
HRTIMER_MODE_REL_PINNED); HRTIMER_MODE_REL_PINNED);
/* initialize timestamp */ /* initialize timestamp */
@ -386,7 +387,7 @@ static int watchdog_should_run(unsigned int cpu)
/* /*
* The watchdog thread function - touches the timestamp. * The watchdog thread function - touches the timestamp.
* *
* It only runs once every get_sample_period() seconds (4 seconds by * It only runs once every sample_period seconds (4 seconds by
* default) to reset the softlockup timestamp. If this gets delayed * default) to reset the softlockup timestamp. If this gets delayed
* for more than 2*watchdog_thresh seconds then the debug-printout * for more than 2*watchdog_thresh seconds then the debug-printout
* triggers in watchdog_timer_fn(). * triggers in watchdog_timer_fn().
@ -519,6 +520,7 @@ int proc_dowatchdog(struct ctl_table *table, int write,
if (ret || !write) if (ret || !write)
return ret; return ret;
set_sample_period();
if (watchdog_enabled && watchdog_thresh) if (watchdog_enabled && watchdog_thresh)
watchdog_enable_all_cpus(); watchdog_enable_all_cpus();
else else
@ -540,6 +542,7 @@ static struct smp_hotplug_thread watchdog_threads = {
void __init lockup_detector_init(void) void __init lockup_detector_init(void)
{ {
set_sample_period();
if (smpboot_register_percpu_thread(&watchdog_threads)) { if (smpboot_register_percpu_thread(&watchdog_threads)) {
pr_err("Failed to create watchdog threads, disabled\n"); pr_err("Failed to create watchdog threads, disabled\n");
watchdog_disabled = -ENODEV; watchdog_disabled = -ENODEV;