// SPDX-License-Identifier: GPL-2.0+/* * This file contains the functions which manage clocksource drivers. * * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com) */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/device.h>#include <linux/clocksource.h>#include <linux/init.h>#include <linux/module.h>#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */#include <linux/tick.h>#include <linux/kthread.h>#include <linux/prandom.h>#include <linux/cpu.h> #include "tick-internal.h"#include "timekeeping_internal.h" /** * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks * @mult: pointer to mult variable * @shift: pointer to shift variable * @from: frequency to convert from * @to: frequency to convert to * @maxsec: guaranteed runtime conversion range in seconds * * The function evaluates the shift/mult pair for the scaled math * operations of clocksources and clockevents. * * @to and @from are frequency values in HZ. For clock sources @to is * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock * event @to is the counter frequency and @from is NSEC_PER_SEC. * * The @maxsec conversion range argument controls the time frame in * seconds which must be covered by the runtime conversion with the * calculated mult and shift factors. This guarantees that no 64bit * overflow happens when the input value of the conversion is * multiplied with the calculated mult factor. Larger ranges may * reduce the conversion accuracy by choosing smaller mult and shift * factors. */voidclocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec){ u64 tmp; u32 sft, sftacc= 32; /* * Calculate the shift factor which is limiting the conversion * range: */ tmp = ((u64)maxsec * from) >> 32; while (tmp) { tmp >>=1; sftacc--; } /* * Find the conversion shift/mult pair which has the best * accuracy and fits the maxsec conversion range: */ for (sft = 32; sft > 0; sft--) { tmp = (u64) to << sft; tmp += from / 2; do_div(tmp, from); if ((tmp >> sftacc) == 0) break; } *mult = tmp; *shift = sft;}EXPORT_SYMBOL_GPL(clocks_calc_mult_shift); /*[Clocksource internal variables]--------- * curr_clocksource: * currently selected clocksource. * suspend_clocksource: * used to calculate the suspend time. * clocksource_list: * linked list with the registered clocksources * clocksource_mutex: * protects manipulations to curr_clocksource and the clocksource_list * override_name: * Name of the user-specified clocksource. */static struct clocksource *curr_clocksource;static struct clocksource *suspend_clocksource;static LIST_HEAD(clocksource_list);static DEFINE_MUTEX(clocksource_mutex);static char override_name[CS_NAME_LEN];static int finished_booting;static u64 suspend_start; /* * Threshold: 0.0312s, when doubled: 0.0625s. * Also a default for cs->uncertainty_margin when registering clocks. */#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5) /* * Maximum permissible delay between two readouts of the watchdog * clocksource surrounding a read of the clocksource being validated. * This delay could be due to SMIs, NMIs, or to VCPU preemptions. Used as * a lower bound for cs->uncertainty_margin values when registering clocks. */#define WATCHDOG_MAX_SKEW (50 * NSEC_PER_USEC) #ifdef CONFIG_CLOCKSOURCE_WATCHDOGstatic void clocksource_watchdog_work(struct work_struct *work);static void clocksource_select(void); static LIST_HEAD(watchdog_list);static struct clocksource *watchdog;static struct timer_list watchdog_timer;static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);static DEFINE_SPINLOCK(watchdog_lock);static int watchdog_running;static atomic_t watchdog_reset_pending; static inline void clocksource_watchdog_lock(unsigned long *flags){ spin_lock_irqsave(&watchdog_lock, *flags);} static inline void clocksource_watchdog_unlock(unsigned long *flags){ spin_unlock_irqrestore(&watchdog_lock, *flags);} static int clocksource_watchdog_kthread(void *data);static void __clocksource_change_rating(struct clocksource *cs, int rating); /* * Interval: 0.5sec. */#define WATCHDOG_INTERVAL (HZ >> 1) static void clocksource_watchdog_work(struct work_struct *work){ /* * We cannot directly run clocksource_watchdog_kthread() here, because * clocksource_select() calls timekeeping_notify() which uses * stop_machine(). One cannot use stop_machine() from a workqueue() due * lock inversions wrt CPU hotplug. * * Also, we only ever run this work once or twice during the lifetime * of the kernel, so there is no point in creating a more permanent * kthread for this. * * If kthread_run fails the next watchdog scan over the * watchdog_list will find the unstable clock again. */ kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");} static void __clocksource_unstable(struct clocksource *cs){ cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); cs->flags |= CLOCK_SOURCE_UNSTABLE; /* * If the clocksource is registered clocksource_watchdog_kthread() will * re-rate and re-select. */ if (list_empty(&cs->list)) { cs->rating = 0; return; } if (cs->mark_unstable) cs->mark_unstable(cs); /* kick clocksource_watchdog_kthread() */ if (finished_booting) schedule_work(&watchdog_work);} /** * clocksource_mark_unstable - mark clocksource unstable via watchdog * @cs: clocksource to be marked unstable * * This function is called by the x86 TSC code to mark clocksources as unstable; * it defers demotion and re-selection to a kthread. */void clocksource_mark_unstable(struct clocksource *cs){ unsigned long flags; spin_lock_irqsave(&watchdog_lock, flags); if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) { if (!list_empty(&cs->list) && list_empty(&cs->wd_list)) list_add(&cs->wd_list, &watchdog_list); __clocksource_unstable(cs); } spin_unlock_irqrestore(&watchdog_lock, flags);} ulong max_cswd_read_retries = 3;module_param(max_cswd_read_retries, ulong, 0644);EXPORT_SYMBOL_GPL(max_cswd_read_retries);static int verify_n_cpus = 8;module_param(verify_n_cpus, int, 0644); static bool cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow){ unsigned int nretries; u64 wd_end, wd_delta; int64_t wd_delay; for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) { local_irq_disable(); *wdnow = watchdog->read(watchdog); *csnow = cs->read(cs); wd_end = watchdog->read(watchdog); local_irq_enable(); wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask); wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift); if (wd_delay <= WATCHDOG_MAX_SKEW) { if (nretries > 1 || nretries >= max_cswd_read_retries) { pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n", smp_processor_id(), watchdog->name, nretries); } return true; } } pr_warn("timekeeping watchdog on CPU%d: %s read-back delay of %lldns, attempt %d, marking unstable\n", smp_processor_id(), watchdog->name, wd_delay, nretries); return false;} static u64 csnow_mid;static cpumask_t cpus_ahead;static cpumask_t cpus_behind;static cpumask_t cpus_chosen; static void clocksource_verify_choose_cpus(void){ int cpu, i, n = verify_n_cpus; if (n < 0) { /* Check all of the CPUs. */ cpumask_copy(&cpus_chosen, cpu_online_mask); cpumask_clear_cpu(smp_processor_id(), &cpus_chosen); return; } /* If no checking desired, or no other CPU to check, leave. */ cpumask_clear(&cpus_chosen); if (n == 0 || num_online_cpus() <= 1) return; /* Make sure to select at least one CPU other than the current CPU. */ cpu = cpumask_next(-1, cpu_online_mask); if (cpu == smp_processor_id()) cpu = cpumask_next(cpu, cpu_online_mask); if (WARN_ON_ONCE(cpu >= nr_cpu_ids)) return; cpumask_set_cpu(cpu, &cpus_chosen); /* Force a sane value for the boot parameter. */ if (n > nr_cpu_ids) n = nr_cpu_ids; /* * Randomly select the specified number of CPUs. If the same * CPU is selected multiple times, that CPU is checked only once, * and no replacement CPU is selected. This gracefully handles * situations where verify_n_cpus is greater than the number of * CPUs that are currently online. */ for (i = 1; i < n; i++) { cpu = prandom_u32() % nr_cpu_ids; cpu = cpumask_next(cpu - 1, cpu_online_mask); if (cpu >= nr_cpu_ids) cpu = cpumask_next(-1, cpu_online_mask); if (!WARN_ON_ONCE(cpu >= nr_cpu_ids)) cpumask_set_cpu(cpu, &cpus_chosen); } /* Don't verify ourselves. */ cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);} static void clocksource_verify_one_cpu(void *csin){ struct clocksource *cs = (struct clocksource *)csin; csnow_mid = cs->read(cs);} void clocksource_verify_percpu(struct clocksource *cs){ int64_t cs_nsec, cs_nsec_max = 0, cs_nsec_min = LLONG_MAX; u64 csnow_begin, csnow_end; int cpu, testcpu; s64 delta; if (verify_n_cpus == 0) return; cpumask_clear(&cpus_ahead); cpumask_clear(&cpus_behind); cpus_read_lock(); preempt_disable(); clocksource_verify_choose_cpus(); if (cpumask_weight(&cpus_chosen) == 0) { preempt_enable(); cpus_read_unlock(); pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name); return; } testcpu = smp_processor_id(); pr_warn("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n", cs->name, testcpu, cpumask_pr_args(&cpus_chosen)); for_each_cpu(cpu, &cpus_chosen) { if (cpu == testcpu) continue; csnow_begin = cs->read(cs); smp_call_function_single(cpu, clocksource_verify_one_cpu, cs, 1); csnow_end = cs->read(cs); delta = (s64)((csnow_mid - csnow_begin) & cs->mask); if (delta < 0) cpumask_set_cpu(cpu, &cpus_behind); delta = (csnow_end - csnow_mid) & cs->mask; if (delta < 0) cpumask_set_cpu(cpu, &cpus_ahead); delta = clocksource_delta(csnow_end, csnow_begin, cs->mask); cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift); if (cs_nsec > cs_nsec_max) cs_nsec_max = cs_nsec; if (cs_nsec < cs_nsec_min) cs_nsec_min = cs_nsec; } preempt_enable(); cpus_read_unlock(); if (!cpumask_empty(&cpus_ahead)) pr_warn(" CPUs %*pbl ahead of CPU %d for clocksource %s.\n", cpumask_pr_args(&cpus_ahead), testcpu, cs->name); if (!cpumask_empty(&cpus_behind)) pr_warn(" CPUs %*pbl behind CPU %d for clocksource %s.\n", cpumask_pr_args(&cpus_behind), testcpu, cs->name); if (!cpumask_empty(&cpus_ahead) || !cpumask_empty(&cpus_behind)) pr_warn(" CPU %d check durations %lldns - %lldns for clocksource %s.\n", testcpu, cs_nsec_min, cs_nsec_max, cs->name);}EXPORT_SYMBOL_GPL(clocksource_verify_percpu); static void clocksource_watchdog(struct timer_list *unused){ u64 csnow, wdnow, cslast, wdlast, delta; int next_cpu, reset_pending; int64_t wd_nsec, cs_nsec; struct clocksource *cs; u32 md; spin_lock(&watchdog_lock); if (!watchdog_running) goto out; reset_pending = atomic_read(&watchdog_reset_pending); list_for_each_entry(cs, &watchdog_list, wd_list) { /* Clocksource already marked unstable? */ if (cs->flags & CLOCK_SOURCE_UNSTABLE) { if (finished_booting) schedule_work(&watchdog_work); continue; } if (!cs_watchdog_read(cs, &csnow, &wdnow)) { /* Clock readout unreliable, so give it up. */ __clocksource_unstable(cs); continue; } /* Clocksource initialized ? */ if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) || atomic_read(&watchdog_reset_pending)) { cs->flags |= CLOCK_SOURCE_WATCHDOG; cs->wd_last = wdnow; cs->cs_last = csnow; continue; } delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask); wd_nsec = clocksource_cyc2ns(delta, watchdog->mult, watchdog->shift); delta = clocksource_delta(csnow, cs->cs_last, cs->mask); cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift); wdlast = cs->wd_last; /* save these in case we print them */ cslast = cs->cs_last; cs->cs_last = csnow; cs->wd_last = wdnow; if (atomic_read(&watchdog_reset_pending)) continue; /* Check the deviation from the watchdog clocksource. */ md = cs->uncertainty_margin + watchdog->uncertainty_margin; if (abs(cs_nsec - wd_nsec) > md) { pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n", smp_processor_id(), cs->name); pr_warn(" '%s' wd_nsec: %lld wd_now: %llx wd_last: %llx mask: %llx\n", watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask); pr_warn(" '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n", cs->name, cs_nsec, csnow, cslast, cs->mask); if (curr_clocksource == cs) pr_warn(" '%s' is current clocksource.\n", cs->name); else if (curr_clocksource) pr_warn(" '%s' (not '%s') is current clocksource.\n", curr_clocksource->name, cs->name); else pr_warn(" No current clocksource.\n"); __clocksource_unstable(cs); continue; } if (cs == curr_clocksource && cs->tick_stable) cs->tick_stable(cs); if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) && (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) { /* Mark it valid for high-res. */ cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; /* * clocksource_done_booting() will sort it if * finished_booting is not set yet. */ if (!finished_booting) continue; /* * If this is not the current clocksource let * the watchdog thread reselect it. Due to the * change to high res this clocksource might * be preferred now. If it is the current * clocksource let the tick code know about * that change. */ if (cs != curr_clocksource) { cs->flags |= CLOCK_SOURCE_RESELECT; schedule_work(&watchdog_work); } else { tick_clock_notify(); } } } /* * We only clear the watchdog_reset_pending, when we did a * full cycle through all clocksources. */ if (reset_pending) atomic_dec(&watchdog_reset_pending); /* * Cycle through CPUs to check if the CPUs stay synchronized * to each other. */ next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask); if (next_cpu >= nr_cpu_ids) next_cpu = cpumask_first(cpu_online_mask); /* * Arm timer if not already pending: could race with concurrent * pair clocksource_stop_watchdog() clocksource_start_watchdog(). */ if (!timer_pending(&watchdog_timer)) { watchdog_timer.expires += WATCHDOG_INTERVAL; add_timer_on(&watchdog_timer, next_cpu); }out: spin_unlock(&watchdog_lock);} static inline void clocksource_start_watchdog(void){ if (watchdog_running || !watchdog || list_empty(&watchdog_list)) return; timer_setup(&watchdog_timer, clocksource_watchdog, 0); watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask)); watchdog_running = 1;} static inline void clocksource_stop_watchdog(void){ if (!watchdog_running || (watchdog && !list_empty(&watchdog_list))) return; del_timer(&watchdog_timer); watchdog_running = 0;}Lines 1–500 of 1439. 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// SPDX-License-Identifier: GPL-2.0+ /* * This file contains the functions which manage clocksource drivers. * * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com) */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/device.h> #include <linux/clocksource.h> #include <linux/init.h> #include <linux/module.h> #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ #include <linux/tick.h> #include <linux/kthread.h> #include <linux/prandom.h> #include <linux/cpu.h> #include "tick-internal.h" #include "timekeeping_internal.h" /** * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks * @mult: pointer to mult variable * @shift: pointer to shift variable * @from: frequency to convert from * @to: frequency to convert to * @maxsec: guaranteed runtime conversion range in seconds * * The function evaluates the shift/mult pair for the scaled math * operations of clocksources and clockevents. * * @to and @from are frequency values in HZ. For clock sources @to is * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock * event @to is the counter frequency and @from is NSEC_PER_SEC. * * The @maxsec conversion range argument controls the time frame in * seconds which must be covered by the runtime conversion with the * calculated mult and shift factors. This guarantees that no 64bit * overflow happens when the input value of the conversion is * multiplied with the calculated mult factor. Larger ranges may * reduce the conversion accuracy by choosing smaller mult and shift * factors. */ void clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec) { u64 tmp; u32 sft, sftacc= 32; /* * Calculate the shift factor which is limiting the conversion * range: */ tmp = ((u64)maxsec * from) >> 32; while (tmp) { tmp >>=1; sftacc--; } /* * Find the conversion shift/mult pair which has the best * accuracy and fits the maxsec conversion range: */ for (sft = 32; sft > 0; sft--) { tmp = (u64) to << sft; tmp += from / 2; do_div(tmp, from); if ((tmp >> sftacc) == 0) break; } *mult = tmp; *shift = sft; } EXPORT_SYMBOL_GPL(clocks_calc_mult_shift); /*[Clocksource internal variables]--------- * curr_clocksource: * currently selected clocksource. * suspend_clocksource: * used to calculate the suspend time. * clocksource_list: * linked list with the registered clocksources * clocksource_mutex: * protects manipulations to curr_clocksource and the clocksource_list * override_name: * Name of the user-specified clocksource. */ static struct clocksource *curr_clocksource; static struct clocksource *suspend_clocksource; static LIST_HEAD(clocksource_list); static DEFINE_MUTEX(clocksource_mutex); static char override_name[CS_NAME_LEN]; static int finished_booting; static u64 suspend_start; /* * Threshold: 0.0312s, when doubled: 0.0625s. * Also a default for cs->uncertainty_margin when registering clocks. */ #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5) /* * Maximum permissible delay between two readouts of the watchdog * clocksource surrounding a read of the clocksource being validated. * This delay could be due to SMIs, NMIs, or to VCPU preemptions. Used as * a lower bound for cs->uncertainty_margin values when registering clocks. */ #define WATCHDOG_MAX_SKEW (50 * NSEC_PER_USEC) #ifdef CONFIG_CLOCKSOURCE_WATCHDOG static void clocksource_watchdog_work(struct work_struct *work); static void clocksource_select(void); static LIST_HEAD(watchdog_list); static struct clocksource *watchdog; static struct timer_list watchdog_timer; static DECLARE_WORK(watchdog_work, clocksource_watchdog_work); static DEFINE_SPINLOCK(watchdog_lock); static int watchdog_running; static atomic_t watchdog_reset_pending; static inline void clocksource_watchdog_lock(unsigned long *flags) { spin_lock_irqsave(&watchdog_lock, *flags); } static inline void clocksource_watchdog_unlock(unsigned long *flags) { spin_unlock_irqrestore(&watchdog_lock, *flags); } static int clocksource_watchdog_kthread(void *data); static void __clocksource_change_rating(struct clocksource *cs, int rating); /* * Interval: 0.5sec. */ #define WATCHDOG_INTERVAL (HZ >> 1) static void clocksource_watchdog_work(struct work_struct *work) { /* * We cannot directly run clocksource_watchdog_kthread() here, because * clocksource_select() calls timekeeping_notify() which uses * stop_machine(). One cannot use stop_machine() from a workqueue() due * lock inversions wrt CPU hotplug. * * Also, we only ever run this work once or twice during the lifetime * of the kernel, so there is no point in creating a more permanent * kthread for this. * * If kthread_run fails the next watchdog scan over the * watchdog_list will find the unstable clock again. */ kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog"); } static void __clocksource_unstable(struct clocksource *cs) { cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); cs->flags |= CLOCK_SOURCE_UNSTABLE; /* * If the clocksource is registered clocksource_watchdog_kthread() will * re-rate and re-select. */ if (list_empty(&cs->list)) { cs->rating = 0; return; } if (cs->mark_unstable) cs->mark_unstable(cs); /* kick clocksource_watchdog_kthread() */ if (finished_booting) schedule_work(&watchdog_work); } /** * clocksource_mark_unstable - mark clocksource unstable via watchdog * @cs: clocksource to be marked unstable * * This function is called by the x86 TSC code to mark clocksources as unstable; * it defers demotion and re-selection to a kthread. */ void clocksource_mark_unstable(struct clocksource *cs) { unsigned long flags; spin_lock_irqsave(&watchdog_lock, flags); if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) { if (!list_empty(&cs->list) && list_empty(&cs->wd_list)) list_add(&cs->wd_list, &watchdog_list); __clocksource_unstable(cs); } spin_unlock_irqrestore(&watchdog_lock, flags); } ulong max_cswd_read_retries = 3; module_param(max_cswd_read_retries, ulong, 0644); EXPORT_SYMBOL_GPL(max_cswd_read_retries); static int verify_n_cpus = 8; module_param(verify_n_cpus, int, 0644); static bool cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow) { unsigned int nretries; u64 wd_end, wd_delta; int64_t wd_delay; for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) { local_irq_disable(); *wdnow = watchdog->read(watchdog); *csnow = cs->read(cs); wd_end = watchdog->read(watchdog); local_irq_enable(); wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask); wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift); if (wd_delay <= WATCHDOG_MAX_SKEW) { if (nretries > 1 || nretries >= max_cswd_read_retries) { pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n", smp_processor_id(), watchdog->name, nretries); } return true; } } pr_warn("timekeeping watchdog on CPU%d: %s read-back delay of %lldns, attempt %d, marking unstable\n", smp_processor_id(), watchdog->name, wd_delay, nretries); return false; } static u64 csnow_mid; static cpumask_t cpus_ahead; static cpumask_t cpus_behind; static cpumask_t cpus_chosen; static void clocksource_verify_choose_cpus(void) { int cpu, i, n = verify_n_cpus; if (n < 0) { /* Check all of the CPUs. */ cpumask_copy(&cpus_chosen, cpu_online_mask); cpumask_clear_cpu(smp_processor_id(), &cpus_chosen); return; } /* If no checking desired, or no other CPU to check, leave. */ cpumask_clear(&cpus_chosen); if (n == 0 || num_online_cpus() <= 1) return; /* Make sure to select at least one CPU other than the current CPU. */ cpu = cpumask_next(-1, cpu_online_mask); if (cpu == smp_processor_id()) cpu = cpumask_next(cpu, cpu_online_mask); if (WARN_ON_ONCE(cpu >= nr_cpu_ids)) return; cpumask_set_cpu(cpu, &cpus_chosen); /* Force a sane value for the boot parameter. */ if (n > nr_cpu_ids) n = nr_cpu_ids; /* * Randomly select the specified number of CPUs. If the same * CPU is selected multiple times, that CPU is checked only once, * and no replacement CPU is selected. This gracefully handles * situations where verify_n_cpus is greater than the number of * CPUs that are currently online. */ for (i = 1; i < n; i++) { cpu = prandom_u32() % nr_cpu_ids; cpu = cpumask_next(cpu - 1, cpu_online_mask); if (cpu >= nr_cpu_ids) cpu = cpumask_next(-1, cpu_online_mask); if (!WARN_ON_ONCE(cpu >= nr_cpu_ids)) cpumask_set_cpu(cpu, &cpus_chosen); } /* Don't verify ourselves. */ cpumask_clear_cpu(smp_processor_id(), &cpus_chosen); } static void clocksource_verify_one_cpu(void *csin) { struct clocksource *cs = (struct clocksource *)csin; csnow_mid = cs->read(cs); } void clocksource_verify_percpu(struct clocksource *cs) { int64_t cs_nsec, cs_nsec_max = 0, cs_nsec_min = LLONG_MAX; u64 csnow_begin, csnow_end; int cpu, testcpu; s64 delta; if (verify_n_cpus == 0) return; cpumask_clear(&cpus_ahead); cpumask_clear(&cpus_behind); cpus_read_lock(); preempt_disable(); clocksource_verify_choose_cpus(); if (cpumask_weight(&cpus_chosen) == 0) { preempt_enable(); cpus_read_unlock(); pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name); return; } testcpu = smp_processor_id(); pr_warn("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n", cs->name, testcpu, cpumask_pr_args(&cpus_chosen)); for_each_cpu(cpu, &cpus_chosen) { if (cpu == testcpu) continue; csnow_begin = cs->read(cs); smp_call_function_single(cpu, clocksource_verify_one_cpu, cs, 1); csnow_end = cs->read(cs); delta = (s64)((csnow_mid - csnow_begin) & cs->mask); if (delta < 0) cpumask_set_cpu(cpu, &cpus_behind); delta = (csnow_end - csnow_mid) & cs->mask; if (delta < 0) cpumask_set_cpu(cpu, &cpus_ahead); delta = clocksource_delta(csnow_end, csnow_begin, cs->mask); cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift); if (cs_nsec > cs_nsec_max) cs_nsec_max = cs_nsec; if (cs_nsec < cs_nsec_min) cs_nsec_min = cs_nsec; } preempt_enable(); cpus_read_unlock(); if (!cpumask_empty(&cpus_ahead)) pr_warn(" CPUs %*pbl ahead of CPU %d for clocksource %s.\n", cpumask_pr_args(&cpus_ahead), testcpu, cs->name); if (!cpumask_empty(&cpus_behind)) pr_warn(" CPUs %*pbl behind CPU %d for clocksource %s.\n", cpumask_pr_args(&cpus_behind), testcpu, cs->name); if (!cpumask_empty(&cpus_ahead) || !cpumask_empty(&cpus_behind)) pr_warn(" CPU %d check durations %lldns - %lldns for clocksource %s.\n", testcpu, cs_nsec_min, cs_nsec_max, cs->name); } EXPORT_SYMBOL_GPL(clocksource_verify_percpu); static void clocksource_watchdog(struct timer_list *unused) { u64 csnow, wdnow, cslast, wdlast, delta; int next_cpu, reset_pending; int64_t wd_nsec, cs_nsec; struct clocksource *cs; u32 md; spin_lock(&watchdog_lock); if (!watchdog_running) goto out; reset_pending = atomic_read(&watchdog_reset_pending); list_for_each_entry(cs, &watchdog_list, wd_list) { /* Clocksource already marked unstable? */ if (cs->flags & CLOCK_SOURCE_UNSTABLE) { if (finished_booting) schedule_work(&watchdog_work); continue; } if (!cs_watchdog_read(cs, &csnow, &wdnow)) { /* Clock readout unreliable, so give it up. */ __clocksource_unstable(cs); continue; } /* Clocksource initialized ? */ if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) || atomic_read(&watchdog_reset_pending)) { cs->flags |= CLOCK_SOURCE_WATCHDOG; cs->wd_last = wdnow; cs->cs_last = csnow; continue; } delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask); wd_nsec = clocksource_cyc2ns(delta, watchdog->mult, watchdog->shift); delta = clocksource_delta(csnow, cs->cs_last, cs->mask); cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift); wdlast = cs->wd_last; /* save these in case we print them */ cslast = cs->cs_last; cs->cs_last = csnow; cs->wd_last = wdnow; if (atomic_read(&watchdog_reset_pending)) continue; /* Check the deviation from the watchdog clocksource. */ md = cs->uncertainty_margin + watchdog->uncertainty_margin; if (abs(cs_nsec - wd_nsec) > md) { pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n", smp_processor_id(), cs->name); pr_warn(" '%s' wd_nsec: %lld wd_now: %llx wd_last: %llx mask: %llx\n", watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask); pr_warn(" '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n", cs->name, cs_nsec, csnow, cslast, cs->mask); if (curr_clocksource == cs) pr_warn(" '%s' is current clocksource.\n", cs->name); else if (curr_clocksource) pr_warn(" '%s' (not '%s') is current clocksource.\n", curr_clocksource->name, cs->name); else pr_warn(" No current clocksource.\n"); __clocksource_unstable(cs); continue; } if (cs == curr_clocksource && cs->tick_stable) cs->tick_stable(cs); if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) && (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) { /* Mark it valid for high-res. */ cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; /* * clocksource_done_booting() will sort it if * finished_booting is not set yet. */ if (!finished_booting) continue; /* * If this is not the current clocksource let * the watchdog thread reselect it. Due to the * change to high res this clocksource might * be preferred now. If it is the current * clocksource let the tick code know about * that change. */ if (cs != curr_clocksource) { cs->flags |= CLOCK_SOURCE_RESELECT; schedule_work(&watchdog_work); } else { tick_clock_notify(); } } } /* * We only clear the watchdog_reset_pending, when we did a * full cycle through all clocksources. */ if (reset_pending) atomic_dec(&watchdog_reset_pending); /* * Cycle through CPUs to check if the CPUs stay synchronized * to each other. */ next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask); if (next_cpu >= nr_cpu_ids) next_cpu = cpumask_first(cpu_online_mask); /* * Arm timer if not already pending: could race with concurrent * pair clocksource_stop_watchdog() clocksource_start_watchdog(). */ if (!timer_pending(&watchdog_timer)) { watchdog_timer.expires += WATCHDOG_INTERVAL; add_timer_on(&watchdog_timer, next_cpu); } out: spin_unlock(&watchdog_lock); } static inline void clocksource_start_watchdog(void) { if (watchdog_running || !watchdog || list_empty(&watchdog_list)) return; timer_setup(&watchdog_timer, clocksource_watchdog, 0); watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask)); watchdog_running = 1; } static inline void clocksource_stop_watchdog(void) { if (!watchdog_running || (watchdog && !list_empty(&watchdog_list))) return; del_timer(&watchdog_timer); watchdog_running = 0; }