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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Detect hard and soft lockups on a system
  *
  * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
  *
  * Note: Most of this code is borrowed heavily from the original softlockup
  * detector, so thanks to Ingo for the initial implementation.
  * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
  * to those contributors as well.
  */
 
 #define pr_fmt(fmt) "watchdog: " fmt
 
 #include <linux/mm.h>
 #include <linux/cpu.h>
 #include <linux/nmi.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/sysctl.h>
 #include <linux/tick.h>
 #include <linux/sched/clock.h>
 #include <linux/sched/debug.h>
 #include <linux/sched/isolation.h>
 #include <linux/stop_machine.h>
 
 #include <asm/irq_regs.h>
 #include <linux/kvm_para.h>
 
 static DEFINE_MUTEX(watchdog_mutex);
 
 #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
 # define WATCHDOG_DEFAULT   (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED)
 # define NMI_WATCHDOG_DEFAULT   1
 #else
 # define WATCHDOG_DEFAULT   (SOFT_WATCHDOG_ENABLED)
 # define NMI_WATCHDOG_DEFAULT   0
 #endif
 
 unsigned long __read_mostly watchdog_enabled;
 int __read_mostly watchdog_user_enabled = 1;
 int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT;
 int __read_mostly soft_watchdog_user_enabled = 1;
 int __read_mostly watchdog_thresh = 10;
 static int __read_mostly nmi_watchdog_available;
 
 struct cpumask watchdog_cpumask __read_mostly;
 unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
 
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 
 # ifdef CONFIG_SMP
 int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
 # endif /* CONFIG_SMP */
 
 /*
  * Should we panic when a soft-lockup or hard-lockup occurs:
  */
 unsigned int __read_mostly hardlockup_panic =
             IS_ENABLED(CONFIG_BOOTPARAM_HARDLOCKUP_PANIC);
 /*
  * We may not want to enable hard lockup detection by default in all cases,
  * for example when running the kernel as a guest on a hypervisor. In these
  * cases this function can be called to disable hard lockup detection. This
  * function should only be executed once by the boot processor before the
  * kernel command line parameters are parsed, because otherwise it is not
  * possible to override this in hardlockup_panic_setup().
  */
 void __init hardlockup_detector_disable(void)
 {
     nmi_watchdog_user_enabled = 0;
 }
 
 static int __init hardlockup_panic_setup(char *str)
 {
     if (!strncmp(str, "panic", 5))
         hardlockup_panic = 1;
     else if (!strncmp(str, "nopanic", 7))
         hardlockup_panic = 0;
     else if (!strncmp(str, "0", 1))
         nmi_watchdog_user_enabled = 0;
     else if (!strncmp(str, "1", 1))
         nmi_watchdog_user_enabled = 1;
     return 1;
 }
 __setup("nmi_watchdog=", hardlockup_panic_setup);
 
 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 
 /*
  * These functions can be overridden if an architecture implements its
  * own hardlockup detector.
  *
  * watchdog_nmi_enable/disable can be implemented to start and stop when
  * softlockup watchdog start and stop. The arch must select the
  * SOFTLOCKUP_DETECTOR Kconfig.
  */
 int __weak watchdog_nmi_enable(unsigned int cpu)
 {
     hardlockup_detector_perf_enable();
     return 0;
 }
 
 void __weak watchdog_nmi_disable(unsigned int cpu)
 {
     hardlockup_detector_perf_disable();
 }
 
 /* Return 0, if a NMI watchdog is available. Error code otherwise */
 int __weak __init watchdog_nmi_probe(void)
 {
     return hardlockup_detector_perf_init();
 }
 
 /**
  * watchdog_nmi_stop - Stop the watchdog for reconfiguration
  *
  * The reconfiguration steps are:
  * watchdog_nmi_stop();
  * update_variables();
  * watchdog_nmi_start();
  */
 void __weak watchdog_nmi_stop(void) { }
 
 /**
  * watchdog_nmi_start - Start the watchdog after reconfiguration
  *
  * Counterpart to watchdog_nmi_stop().
  *
  * The following variables have been updated in update_variables() and
  * contain the currently valid configuration:
  * - watchdog_enabled
  * - watchdog_thresh
  * - watchdog_cpumask
  */
 void __weak watchdog_nmi_start(void) { }
 
 /**
  * lockup_detector_update_enable - Update the sysctl enable bit
  *
  * Caller needs to make sure that the NMI/perf watchdogs are off, so this
  * can't race with watchdog_nmi_disable().
  */
 static void lockup_detector_update_enable(void)
 {
     watchdog_enabled = 0;
     if (!watchdog_user_enabled)
         return;
     if (nmi_watchdog_available && nmi_watchdog_user_enabled)
         watchdog_enabled |= NMI_WATCHDOG_ENABLED;
     if (soft_watchdog_user_enabled)
         watchdog_enabled |= SOFT_WATCHDOG_ENABLED;
 }
 
 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 
 /*
  * Delay the soflockup report when running a known slow code.
  * It does _not_ affect the timestamp of the last successdul reschedule.
  */
 #define SOFTLOCKUP_DELAY_REPORT ULONG_MAX
 
 #ifdef CONFIG_SMP
 int __read_mostly sysctl_softlockup_all_cpu_backtrace;
 #endif
 
 static struct cpumask watchdog_allowed_mask __read_mostly;
 
 /* Global variables, exported for sysctl */
 unsigned int __read_mostly softlockup_panic =
             IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
 
 static bool softlockup_initialized __read_mostly;
 static u64 __read_mostly sample_period;
 
 /* Timestamp taken after the last successful reschedule. */
 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 /* Timestamp of the last softlockup report. */
 static DEFINE_PER_CPU(unsigned long, watchdog_report_ts);
 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 static unsigned long soft_lockup_nmi_warn;
 
 static int __init nowatchdog_setup(char *str)
 {
     watchdog_user_enabled = 0;
     return 1;
 }
 __setup("nowatchdog", nowatchdog_setup);
 
 static int __init nosoftlockup_setup(char *str)
 {
     soft_watchdog_user_enabled = 0;
     return 1;
 }
 __setup("nosoftlockup", nosoftlockup_setup);
 
 static int __init watchdog_thresh_setup(char *str)
 {
     get_option(&str, &watchdog_thresh);
     return 1;
 }
 __setup("watchdog_thresh=", watchdog_thresh_setup);
 
 static void __lockup_detector_cleanup(void);
 
 /*
  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
  * lockups can have false positives under extreme conditions. So we generally
  * want a higher threshold for soft lockups than for hard lockups. So we couple
  * the thresholds with a factor: we make the soft threshold twice the amount of
  * time the hard threshold is.
  */
 static int get_softlockup_thresh(void)
 {
     return watchdog_thresh * 2;
 }
 
 /*
  * Returns seconds, approximately.  We don't need nanosecond
  * resolution, and we don't need to waste time with a big divide when
  * 2^30ns == 1.074s.
  */
 static unsigned long get_timestamp(void)
 {
     return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
 }
 
 static void set_sample_period(void)
 {
     /*
      * convert watchdog_thresh from seconds to ns
      * the divide by 5 is to give hrtimer several chances (two
      * or three with the current relation between the soft
      * and hard thresholds) to increment before the
      * hardlockup detector generates a warning
      */
     sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
     watchdog_update_hrtimer_threshold(sample_period);
 }
 
 static void update_report_ts(void)
 {
     __this_cpu_write(watchdog_report_ts, get_timestamp());
 }
 
 /* Commands for resetting the watchdog */
 static void update_touch_ts(void)
 {
     __this_cpu_write(watchdog_touch_ts, get_timestamp());
     update_report_ts();
 }
 
 /**
  * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
  *
  * Call when the scheduler may have stalled for legitimate reasons
  * preventing the watchdog task from executing - e.g. the scheduler
  * entering idle state.  This should only be used for scheduler events.
  * Use touch_softlockup_watchdog() for everything else.
  */
 notrace void touch_softlockup_watchdog_sched(void)
 {
     /*
      * Preemption can be enabled.  It doesn't matter which CPU's watchdog
      * report period gets restarted here, so use the raw_ operation.
      */
     raw_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
 }
 
 notrace void touch_softlockup_watchdog(void)
 {
     touch_softlockup_watchdog_sched();
     wq_watchdog_touch(raw_smp_processor_id());
 }
 EXPORT_SYMBOL(touch_softlockup_watchdog);
 
 void touch_all_softlockup_watchdogs(void)
 {
     int cpu;
 
     /*
      * watchdog_mutex cannpt be taken here, as this might be called
      * from (soft)interrupt context, so the access to
      * watchdog_allowed_cpumask might race with a concurrent update.
      *
      * The watchdog time stamp can race against a concurrent real
      * update as well, the only side effect might be a cycle delay for
      * the softlockup check.
      */
     for_each_cpu(cpu, &watchdog_allowed_mask) {
         per_cpu(watchdog_report_ts, cpu) = SOFTLOCKUP_DELAY_REPORT;
         wq_watchdog_touch(cpu);
     }
 }
 
 void touch_softlockup_watchdog_sync(void)
 {
     __this_cpu_write(softlockup_touch_sync, true);
     __this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
 }
 
 static int is_softlockup(unsigned long touch_ts,
              unsigned long period_ts,
              unsigned long now)
 {
     if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
         /* Warn about unreasonable delays. */
         if (time_after(now, period_ts + get_softlockup_thresh()))
             return now - touch_ts;
     }
     return 0;
 }
 
 /* watchdog detector functions */
 bool is_hardlockup(void)
 {
     unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
 
     if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
         return true;
 
     __this_cpu_write(hrtimer_interrupts_saved, hrint);
     return false;
 }
 
 static void watchdog_interrupt_count(void)
 {
     __this_cpu_inc(hrtimer_interrupts);
 }
 
 static DEFINE_PER_CPU(struct completion, softlockup_completion);
 static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work);
 
 /*
  * The watchdog feed function - touches the timestamp.
  *
  * It only runs once every sample_period seconds (4 seconds by
  * default) to reset the softlockup timestamp. If this gets delayed
  * for more than 2*watchdog_thresh seconds then the debug-printout
  * triggers in watchdog_timer_fn().
  */
 static int softlockup_fn(void *data)
 {
     update_touch_ts();
     complete(this_cpu_ptr(&softlockup_completion));
 
     return 0;
 }
 
 /* watchdog kicker functions */
 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 {
     unsigned long touch_ts, period_ts, now;
     struct pt_regs *regs = get_irq_regs();
     int duration;
     int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
 
     if (!watchdog_enabled)
         return HRTIMER_NORESTART;
 
     /* kick the hardlockup detector */
     watchdog_interrupt_count();
 
     /* kick the softlockup detector */
     if (completion_done(this_cpu_ptr(&softlockup_completion))) {
         reinit_completion(this_cpu_ptr(&softlockup_completion));
         stop_one_cpu_nowait(smp_processor_id(),
                 softlockup_fn, NULL,
                 this_cpu_ptr(&softlockup_stop_work));
     }
 
     /* .. and repeat */
     hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 
     /*
      * Read the current timestamp first. It might become invalid anytime
      * when a virtual machine is stopped by the host or when the watchog
      * is touched from NMI.
      */
     now = get_timestamp();
     /*
      * If a virtual machine is stopped by the host it can look to
      * the watchdog like a soft lockup. This function touches the watchdog.
      */
     kvm_check_and_clear_guest_paused();
     /*
      * The stored timestamp is comparable with @now only when not touched.
      * It might get touched anytime from NMI. Make sure that is_softlockup()
      * uses the same (valid) value.
      */
     period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts));
 
     /* Reset the interval when touched by known problematic code. */
     if (period_ts == SOFTLOCKUP_DELAY_REPORT) {
         if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
             /*
              * If the time stamp was touched atomically
              * make sure the scheduler tick is up to date.
              */
             __this_cpu_write(softlockup_touch_sync, false);
             sched_clock_tick();
         }
 
         update_report_ts();
         return HRTIMER_RESTART;
     }
 
     /* Check for a softlockup. */
     touch_ts = __this_cpu_read(watchdog_touch_ts);
     duration = is_softlockup(touch_ts, period_ts, now);
     if (unlikely(duration)) {
         /*
          * Prevent multiple soft-lockup reports if one cpu is already
          * engaged in dumping all cpu back traces.
          */
         if (softlockup_all_cpu_backtrace) {
             if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
                 return HRTIMER_RESTART;
         }
 
         /* Start period for the next softlockup warning. */
         update_report_ts();
 
         pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
             smp_processor_id(), duration,
             current->comm, task_pid_nr(current));
         print_modules();
         print_irqtrace_events(current);
         if (regs)
             show_regs(regs);
         else
             dump_stack();
 
         if (softlockup_all_cpu_backtrace) {
             trigger_allbutself_cpu_backtrace();
             clear_bit_unlock(0, &soft_lockup_nmi_warn);
         }
 
         add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
         if (softlockup_panic)
             panic("softlockup: hung tasks");
     }
 
     return HRTIMER_RESTART;
 }
 
 static void watchdog_enable(unsigned int cpu)
 {
     struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
     struct completion *done = this_cpu_ptr(&softlockup_completion);
 
     WARN_ON_ONCE(cpu != smp_processor_id());
 
     init_completion(done);
     complete(done);
 
     /*
      * Start the timer first to prevent the NMI watchdog triggering
      * before the timer has a chance to fire.
      */
     hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
     hrtimer->function = watchdog_timer_fn;
     hrtimer_start(hrtimer, ns_to_ktime(sample_period),
               HRTIMER_MODE_REL_PINNED_HARD);
 
     /* Initialize timestamp */
     update_touch_ts();
     /* Enable the perf event */
     if (watchdog_enabled & NMI_WATCHDOG_ENABLED)
         watchdog_nmi_enable(cpu);
 }
 
 static void watchdog_disable(unsigned int cpu)
 {
     struct hrtimer *hrtimer = this_cpu_ptr(&watchdog_hrtimer);
 
     WARN_ON_ONCE(cpu != smp_processor_id());
 
     /*
      * Disable the perf event first. That prevents that a large delay
      * between disabling the timer and disabling the perf event causes
      * the perf NMI to detect a false positive.
      */
     watchdog_nmi_disable(cpu);
     hrtimer_cancel(hrtimer);
     wait_for_completion(this_cpu_ptr(&softlockup_completion));
 }
 
 static int softlockup_stop_fn(void *data)
 {
     watchdog_disable(smp_processor_id());
     return 0;
 }
 
 static void softlockup_stop_all(void)
 {
     int cpu;
 
     if (!softlockup_initialized)
         return;
 
     for_each_cpu(cpu, &watchdog_allowed_mask)
         smp_call_on_cpu(cpu, softlockup_stop_fn, NULL, false);
 
     cpumask_clear(&watchdog_allowed_mask);
 }
 
 static int softlockup_start_fn(void *data)
 {
     watchdog_enable(smp_processor_id());
     return 0;
 }
 
 static void softlockup_start_all(void)
 {
     int cpu;
 
     cpumask_copy(&watchdog_allowed_mask, &watchdog_cpumask);
     for_each_cpu(cpu, &watchdog_allowed_mask)
         smp_call_on_cpu(cpu, softlockup_start_fn, NULL, false);
 }
 
 int lockup_detector_online_cpu(unsigned int cpu)
 {
     if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
         watchdog_enable(cpu);
     return 0;
 }
 
 int lockup_detector_offline_cpu(unsigned int cpu)
 {
     if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
         watchdog_disable(cpu);
     return 0;
 }
 
 static void __lockup_detector_reconfigure(void)
 {
     cpus_read_lock();
     watchdog_nmi_stop();
 
     softlockup_stop_all();
     set_sample_period();
     lockup_detector_update_enable();
     if (watchdog_enabled && watchdog_thresh)
         softlockup_start_all();
 
     watchdog_nmi_start();
     cpus_read_unlock();
     /*
      * Must be called outside the cpus locked section to prevent
      * recursive locking in the perf code.
      */
     __lockup_detector_cleanup();
 }
 
 void lockup_detector_reconfigure(void)
 {
     mutex_lock(&watchdog_mutex);
     __lockup_detector_reconfigure();
     mutex_unlock(&watchdog_mutex);
 }
 
 /*
  * Create the watchdog infrastructure and configure the detector(s).
  */
 static __init void lockup_detector_setup(void)
 {
     /*
      * If sysctl is off and watchdog got disabled on the command line,
      * nothing to do here.
      */
     lockup_detector_update_enable();
 
     if (!IS_ENABLED(CONFIG_SYSCTL) &&
         !(watchdog_enabled && watchdog_thresh))
         return;
 
     mutex_lock(&watchdog_mutex);
     __lockup_detector_reconfigure();
     softlockup_initialized = true;
     mutex_unlock(&watchdog_mutex);
 }
 
 #else /* CONFIG_SOFTLOCKUP_DETECTOR */
 static void __lockup_detector_reconfigure(void)
 {
     cpus_read_lock();
     watchdog_nmi_stop();
     lockup_detector_update_enable();
     watchdog_nmi_start();
     cpus_read_unlock();
 }
 void lockup_detector_reconfigure(void)
 {
     __lockup_detector_reconfigure();
 }
 static inline void lockup_detector_setup(void)
 {
     __lockup_detector_reconfigure();
 }
 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
 
 static void __lockup_detector_cleanup(void)
 {
     lockdep_assert_held(&watchdog_mutex);
     hardlockup_detector_perf_cleanup();
 }
 
 /**
  * lockup_detector_cleanup - Cleanup after cpu hotplug or sysctl changes
  *
  * Caller must not hold the cpu hotplug rwsem.
  */
 void lockup_detector_cleanup(void)
 {
     mutex_lock(&watchdog_mutex);
     __lockup_detector_cleanup();
     mutex_unlock(&watchdog_mutex);
 }
 
 /**
  * lockup_detector_soft_poweroff - Interface to stop lockup detector(s)
  *
  * Special interface for parisc. It prevents lockup detector warnings from
  * the default pm_poweroff() function which busy loops forever.
  */
 void lockup_detector_soft_poweroff(void)
 {
     watchdog_enabled = 0;
 }
 
 #ifdef CONFIG_SYSCTL
 
 /* Propagate any changes to the watchdog infrastructure */
 static void proc_watchdog_update(void)
 {
     /* Remove impossible cpus to keep sysctl output clean. */
     cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
     __lockup_detector_reconfigure();
 }
 
 /*
  * common function for watchdog, nmi_watchdog and soft_watchdog parameter
  *
  * caller             | table->data points to      | 'which'
  * -------------------|----------------------------|--------------------------
  * proc_watchdog      | watchdog_user_enabled      | NMI_WATCHDOG_ENABLED |
  *                    |                            | SOFT_WATCHDOG_ENABLED
  * -------------------|----------------------------|--------------------------
  * proc_nmi_watchdog  | nmi_watchdog_user_enabled  | NMI_WATCHDOG_ENABLED
  * -------------------|----------------------------|--------------------------
  * proc_soft_watchdog | soft_watchdog_user_enabled | SOFT_WATCHDOG_ENABLED
  */
 static int proc_watchdog_common(int which, struct ctl_table *table, int write,
                 void *buffer, size_t *lenp, loff_t *ppos)
 {
     int err, old, *param = table->data;
 
     mutex_lock(&watchdog_mutex);
 
     if (!write) {
         /*
          * On read synchronize the userspace interface. This is a
          * racy snapshot.
          */
         *param = (watchdog_enabled & which) != 0;
         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
     } else {
         old = READ_ONCE(*param);
         err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
         if (!err && old != READ_ONCE(*param))
             proc_watchdog_update();
     }
     mutex_unlock(&watchdog_mutex);
     return err;
 }
 
 /*
  * /proc/sys/kernel/watchdog
  */
 int proc_watchdog(struct ctl_table *table, int write,
           void *buffer, size_t *lenp, loff_t *ppos)
 {
     return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
                     table, write, buffer, lenp, ppos);
 }
 
 /*
  * /proc/sys/kernel/nmi_watchdog
  */
 int proc_nmi_watchdog(struct ctl_table *table, int write,
               void *buffer, size_t *lenp, loff_t *ppos)
 {
     if (!nmi_watchdog_available && write)
         return -ENOTSUPP;
     return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
                     table, write, buffer, lenp, ppos);
 }
 
 /*
  * /proc/sys/kernel/soft_watchdog
  */
 int proc_soft_watchdog(struct ctl_table *table, int write,
             void *buffer, size_t *lenp, loff_t *ppos)
 {
     return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
                     table, write, buffer, lenp, ppos);
 }
 
 /*
  * /proc/sys/kernel/watchdog_thresh
  */
 int proc_watchdog_thresh(struct ctl_table *table, int write,
              void *buffer, size_t *lenp, loff_t *ppos)
 {
     int err, old;
 
     mutex_lock(&watchdog_mutex);
 
     old = READ_ONCE(watchdog_thresh);
     err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 
     if (!err && write && old != READ_ONCE(watchdog_thresh))
         proc_watchdog_update();
 
     mutex_unlock(&watchdog_mutex);
     return err;
 }
 
 /*
  * The cpumask is the mask of possible cpus that the watchdog can run
  * on, not the mask of cpus it is actually running on.  This allows the
  * user to specify a mask that will include cpus that have not yet
  * been brought online, if desired.
  */
 int proc_watchdog_cpumask(struct ctl_table *table, int write,
               void *buffer, size_t *lenp, loff_t *ppos)
 {
     int err;
 
     mutex_lock(&watchdog_mutex);
 
     err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
     if (!err && write)
         proc_watchdog_update();
 
     mutex_unlock(&watchdog_mutex);
     return err;
 }
 
 static const int sixty = 60;
 
 static struct ctl_table watchdog_sysctls[] = {
     {
         .procname       = "watchdog",
         .data       = &watchdog_user_enabled,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         .proc_handler   = proc_watchdog,
         .extra1     = SYSCTL_ZERO,
         .extra2     = SYSCTL_ONE,
     },
     {
         .procname   = "watchdog_thresh",
         .data       = &watchdog_thresh,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         .proc_handler   = proc_watchdog_thresh,
         .extra1     = SYSCTL_ZERO,
         .extra2     = (void *)&sixty,
     },
     {
         .procname       = "nmi_watchdog",
         .data       = &nmi_watchdog_user_enabled,
         .maxlen     = sizeof(int),
         .mode       = NMI_WATCHDOG_SYSCTL_PERM,
         .proc_handler   = proc_nmi_watchdog,
         .extra1     = SYSCTL_ZERO,
         .extra2     = SYSCTL_ONE,
     },
     {
         .procname   = "watchdog_cpumask",
         .data       = &watchdog_cpumask_bits,
         .maxlen     = NR_CPUS,
         .mode       = 0644,
         .proc_handler   = proc_watchdog_cpumask,
     },
 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
     {
         .procname       = "soft_watchdog",
         .data       = &soft_watchdog_user_enabled,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         .proc_handler   = proc_soft_watchdog,
         .extra1     = SYSCTL_ZERO,
         .extra2     = SYSCTL_ONE,
     },
     {
         .procname   = "softlockup_panic",
         .data       = &softlockup_panic,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         .proc_handler   = proc_dointvec_minmax,
         .extra1     = SYSCTL_ZERO,
         .extra2     = SYSCTL_ONE,
     },
 #ifdef CONFIG_SMP
     {
         .procname   = "softlockup_all_cpu_backtrace",
         .data       = &sysctl_softlockup_all_cpu_backtrace,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         .proc_handler   = proc_dointvec_minmax,
         .extra1     = SYSCTL_ZERO,
         .extra2     = SYSCTL_ONE,
     },
 #endif /* CONFIG_SMP */
 #endif
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
     {
         .procname   = "hardlockup_panic",
         .data       = &hardlockup_panic,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         .proc_handler   = proc_dointvec_minmax,
         .extra1     = SYSCTL_ZERO,
         .extra2     = SYSCTL_ONE,
     },
 #ifdef CONFIG_SMP
     {
         .procname   = "hardlockup_all_cpu_backtrace",
         .data       = &sysctl_hardlockup_all_cpu_backtrace,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         .proc_handler   = proc_dointvec_minmax,
         .extra1     = SYSCTL_ZERO,
         .extra2     = SYSCTL_ONE,
     },
 #endif /* CONFIG_SMP */
 #endif
     {}
 };
 
 static void __init watchdog_sysctl_init(void)
 {
     register_sysctl_init("kernel", watchdog_sysctls);
 }
 #else
 #define watchdog_sysctl_init() do { } while (0)
 #endif /* CONFIG_SYSCTL */
 
 void __init lockup_detector_init(void)
 {
     if (tick_nohz_full_enabled())
         pr_info("Disabling watchdog on nohz_full cores by default\n");
 
     cpumask_copy(&watchdog_cpumask,
              housekeeping_cpumask(HK_TYPE_TIMER));
 
     if (!watchdog_nmi_probe())
         nmi_watchdog_available = true;
     lockup_detector_setup();
     watchdog_sysctl_init();
 }

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