forked from Minki/linux
8fff52fd50
When no timers/hrtimers are pending, the expiry time is set to a special value: 'KTIME_MAX'. This normally happens with NO_HZ_{IDLE|FULL} in both LOWRES/HIGHRES modes. When 'expiry == KTIME_MAX', we either cancel the 'tick-sched' hrtimer (NOHZ_MODE_HIGHRES) or skip reprogramming clockevent device (NOHZ_MODE_LOWRES). But, the clockevent device is already reprogrammed from the tick-handler for next tick. As the clock event device is programmed in ONESHOT mode it will at least fire one more time (unnecessarily). Timers on few implementations (like arm_arch_timer, etc.) only support PERIODIC mode and their drivers emulate ONESHOT over that. Which means that on these platforms we will get spurious interrupts periodically (at last programmed interval rate, normally tick rate). In order to avoid spurious interrupts, the clockevent device should be stopped or its interrupts should be masked. A simple (yet hacky) solution to get this fixed could be: update hrtimer_force_reprogram() to always reprogram clockevent device and update clockevent drivers to STOP generating events (or delay it to max time) when 'expires' is set to KTIME_MAX. But the drawback here is that every clockevent driver has to be hacked for this particular case and its very easy for new ones to miss this. However, Thomas suggested to add an optional state ONESHOT_STOPPED to solve this problem: lkml.org/lkml/2014/5/9/508. This patch adds support for ONESHOT_STOPPED state in clockevents core. It will only be available to drivers that implement the state-specific callbacks instead of the legacy ->set_mode() callback. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Reviewed-by: Preeti U. Murthy <preeti@linux.vnet.ibm.com> Cc: linaro-kernel@lists.linaro.org Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Kevin Hilman <khilman@linaro.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/b8b383a03ac07b13312c16850b5106b82e4245b5.1428031396.git.viresh.kumar@linaro.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
410 lines
9.8 KiB
C
410 lines
9.8 KiB
C
/*
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* kernel/time/timer_list.c
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*
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* List pending timers
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*
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* Copyright(C) 2006, Red Hat, Inc., Ingo Molnar
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/proc_fs.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <linux/sched.h>
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#include <linux/seq_file.h>
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#include <linux/kallsyms.h>
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#include <asm/uaccess.h>
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#include "tick-internal.h"
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struct timer_list_iter {
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int cpu;
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bool second_pass;
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u64 now;
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};
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typedef void (*print_fn_t)(struct seq_file *m, unsigned int *classes);
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DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases);
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/*
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* This allows printing both to /proc/timer_list and
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* to the console (on SysRq-Q):
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*/
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__printf(2, 3)
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static void SEQ_printf(struct seq_file *m, const char *fmt, ...)
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{
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va_list args;
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va_start(args, fmt);
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if (m)
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seq_vprintf(m, fmt, args);
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else
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vprintk(fmt, args);
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va_end(args);
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}
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static void print_name_offset(struct seq_file *m, void *sym)
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{
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char symname[KSYM_NAME_LEN];
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if (lookup_symbol_name((unsigned long)sym, symname) < 0)
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SEQ_printf(m, "<%pK>", sym);
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else
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SEQ_printf(m, "%s", symname);
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}
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static void
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print_timer(struct seq_file *m, struct hrtimer *taddr, struct hrtimer *timer,
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int idx, u64 now)
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{
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#ifdef CONFIG_TIMER_STATS
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char tmp[TASK_COMM_LEN + 1];
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#endif
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SEQ_printf(m, " #%d: ", idx);
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print_name_offset(m, taddr);
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SEQ_printf(m, ", ");
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print_name_offset(m, timer->function);
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SEQ_printf(m, ", S:%02lx", timer->state);
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#ifdef CONFIG_TIMER_STATS
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SEQ_printf(m, ", ");
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print_name_offset(m, timer->start_site);
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memcpy(tmp, timer->start_comm, TASK_COMM_LEN);
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tmp[TASK_COMM_LEN] = 0;
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SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);
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#endif
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SEQ_printf(m, "\n");
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SEQ_printf(m, " # expires at %Lu-%Lu nsecs [in %Ld to %Ld nsecs]\n",
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(unsigned long long)ktime_to_ns(hrtimer_get_softexpires(timer)),
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(unsigned long long)ktime_to_ns(hrtimer_get_expires(timer)),
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(long long)(ktime_to_ns(hrtimer_get_softexpires(timer)) - now),
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(long long)(ktime_to_ns(hrtimer_get_expires(timer)) - now));
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}
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static void
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print_active_timers(struct seq_file *m, struct hrtimer_clock_base *base,
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u64 now)
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{
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struct hrtimer *timer, tmp;
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unsigned long next = 0, i;
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struct timerqueue_node *curr;
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unsigned long flags;
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next_one:
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i = 0;
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raw_spin_lock_irqsave(&base->cpu_base->lock, flags);
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curr = timerqueue_getnext(&base->active);
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/*
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* Crude but we have to do this O(N*N) thing, because
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* we have to unlock the base when printing:
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*/
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while (curr && i < next) {
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curr = timerqueue_iterate_next(curr);
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i++;
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}
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if (curr) {
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timer = container_of(curr, struct hrtimer, node);
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tmp = *timer;
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raw_spin_unlock_irqrestore(&base->cpu_base->lock, flags);
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print_timer(m, timer, &tmp, i, now);
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next++;
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goto next_one;
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}
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raw_spin_unlock_irqrestore(&base->cpu_base->lock, flags);
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}
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static void
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print_base(struct seq_file *m, struct hrtimer_clock_base *base, u64 now)
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{
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SEQ_printf(m, " .base: %pK\n", base);
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SEQ_printf(m, " .index: %d\n", base->index);
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SEQ_printf(m, " .resolution: %u nsecs\n", (unsigned) hrtimer_resolution);
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SEQ_printf(m, " .get_time: ");
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print_name_offset(m, base->get_time);
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SEQ_printf(m, "\n");
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#ifdef CONFIG_HIGH_RES_TIMERS
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SEQ_printf(m, " .offset: %Lu nsecs\n",
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(unsigned long long) ktime_to_ns(base->offset));
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#endif
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SEQ_printf(m, "active timers:\n");
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print_active_timers(m, base, now);
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}
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static void print_cpu(struct seq_file *m, int cpu, u64 now)
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{
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struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
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int i;
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SEQ_printf(m, "cpu: %d\n", cpu);
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for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
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SEQ_printf(m, " clock %d:\n", i);
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print_base(m, cpu_base->clock_base + i, now);
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}
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#define P(x) \
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SEQ_printf(m, " .%-15s: %Lu\n", #x, \
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(unsigned long long)(cpu_base->x))
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#define P_ns(x) \
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SEQ_printf(m, " .%-15s: %Lu nsecs\n", #x, \
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(unsigned long long)(ktime_to_ns(cpu_base->x)))
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#ifdef CONFIG_HIGH_RES_TIMERS
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P_ns(expires_next);
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P(hres_active);
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P(nr_events);
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P(nr_retries);
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P(nr_hangs);
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P(max_hang_time);
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#endif
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#undef P
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#undef P_ns
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#ifdef CONFIG_TICK_ONESHOT
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# define P(x) \
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SEQ_printf(m, " .%-15s: %Lu\n", #x, \
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(unsigned long long)(ts->x))
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# define P_ns(x) \
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SEQ_printf(m, " .%-15s: %Lu nsecs\n", #x, \
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(unsigned long long)(ktime_to_ns(ts->x)))
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{
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struct tick_sched *ts = tick_get_tick_sched(cpu);
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P(nohz_mode);
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P_ns(last_tick);
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P(tick_stopped);
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P(idle_jiffies);
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P(idle_calls);
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P(idle_sleeps);
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P_ns(idle_entrytime);
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P_ns(idle_waketime);
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P_ns(idle_exittime);
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P_ns(idle_sleeptime);
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P_ns(iowait_sleeptime);
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P(last_jiffies);
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P(next_timer);
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P_ns(idle_expires);
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SEQ_printf(m, "jiffies: %Lu\n",
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(unsigned long long)jiffies);
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}
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#endif
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#undef P
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#undef P_ns
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SEQ_printf(m, "\n");
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}
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#ifdef CONFIG_GENERIC_CLOCKEVENTS
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static void
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print_tickdevice(struct seq_file *m, struct tick_device *td, int cpu)
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{
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struct clock_event_device *dev = td->evtdev;
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SEQ_printf(m, "Tick Device: mode: %d\n", td->mode);
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if (cpu < 0)
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SEQ_printf(m, "Broadcast device\n");
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else
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SEQ_printf(m, "Per CPU device: %d\n", cpu);
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SEQ_printf(m, "Clock Event Device: ");
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if (!dev) {
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SEQ_printf(m, "<NULL>\n");
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return;
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}
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SEQ_printf(m, "%s\n", dev->name);
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SEQ_printf(m, " max_delta_ns: %llu\n",
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(unsigned long long) dev->max_delta_ns);
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SEQ_printf(m, " min_delta_ns: %llu\n",
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(unsigned long long) dev->min_delta_ns);
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SEQ_printf(m, " mult: %u\n", dev->mult);
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SEQ_printf(m, " shift: %u\n", dev->shift);
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SEQ_printf(m, " mode: %d\n", dev->mode);
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SEQ_printf(m, " next_event: %Ld nsecs\n",
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(unsigned long long) ktime_to_ns(dev->next_event));
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SEQ_printf(m, " set_next_event: ");
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print_name_offset(m, dev->set_next_event);
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SEQ_printf(m, "\n");
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if (dev->set_mode) {
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SEQ_printf(m, " set_mode: ");
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print_name_offset(m, dev->set_mode);
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SEQ_printf(m, "\n");
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} else {
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if (dev->set_state_shutdown) {
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SEQ_printf(m, " shutdown: ");
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print_name_offset(m, dev->set_state_shutdown);
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SEQ_printf(m, "\n");
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}
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if (dev->set_state_periodic) {
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SEQ_printf(m, " periodic: ");
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print_name_offset(m, dev->set_state_periodic);
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SEQ_printf(m, "\n");
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}
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if (dev->set_state_oneshot) {
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SEQ_printf(m, " oneshot: ");
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print_name_offset(m, dev->set_state_oneshot);
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SEQ_printf(m, "\n");
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}
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if (dev->set_state_oneshot_stopped) {
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SEQ_printf(m, " oneshot stopped: ");
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print_name_offset(m, dev->set_state_oneshot_stopped);
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SEQ_printf(m, "\n");
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}
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if (dev->tick_resume) {
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SEQ_printf(m, " resume: ");
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print_name_offset(m, dev->tick_resume);
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SEQ_printf(m, "\n");
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}
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}
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SEQ_printf(m, " event_handler: ");
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print_name_offset(m, dev->event_handler);
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SEQ_printf(m, "\n");
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SEQ_printf(m, " retries: %lu\n", dev->retries);
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SEQ_printf(m, "\n");
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}
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static void timer_list_show_tickdevices_header(struct seq_file *m)
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{
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#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
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print_tickdevice(m, tick_get_broadcast_device(), -1);
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SEQ_printf(m, "tick_broadcast_mask: %*pb\n",
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cpumask_pr_args(tick_get_broadcast_mask()));
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#ifdef CONFIG_TICK_ONESHOT
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SEQ_printf(m, "tick_broadcast_oneshot_mask: %*pb\n",
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cpumask_pr_args(tick_get_broadcast_oneshot_mask()));
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#endif
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SEQ_printf(m, "\n");
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#endif
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}
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#endif
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static inline void timer_list_header(struct seq_file *m, u64 now)
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{
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SEQ_printf(m, "Timer List Version: v0.8\n");
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SEQ_printf(m, "HRTIMER_MAX_CLOCK_BASES: %d\n", HRTIMER_MAX_CLOCK_BASES);
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SEQ_printf(m, "now at %Ld nsecs\n", (unsigned long long)now);
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SEQ_printf(m, "\n");
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}
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static int timer_list_show(struct seq_file *m, void *v)
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{
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struct timer_list_iter *iter = v;
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if (iter->cpu == -1 && !iter->second_pass)
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timer_list_header(m, iter->now);
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else if (!iter->second_pass)
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print_cpu(m, iter->cpu, iter->now);
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#ifdef CONFIG_GENERIC_CLOCKEVENTS
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else if (iter->cpu == -1 && iter->second_pass)
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timer_list_show_tickdevices_header(m);
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else
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print_tickdevice(m, tick_get_device(iter->cpu), iter->cpu);
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#endif
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return 0;
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}
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void sysrq_timer_list_show(void)
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{
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u64 now = ktime_to_ns(ktime_get());
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int cpu;
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timer_list_header(NULL, now);
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for_each_online_cpu(cpu)
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print_cpu(NULL, cpu, now);
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#ifdef CONFIG_GENERIC_CLOCKEVENTS
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timer_list_show_tickdevices_header(NULL);
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for_each_online_cpu(cpu)
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print_tickdevice(NULL, tick_get_device(cpu), cpu);
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#endif
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return;
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}
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static void *move_iter(struct timer_list_iter *iter, loff_t offset)
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{
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for (; offset; offset--) {
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iter->cpu = cpumask_next(iter->cpu, cpu_online_mask);
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if (iter->cpu >= nr_cpu_ids) {
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#ifdef CONFIG_GENERIC_CLOCKEVENTS
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if (!iter->second_pass) {
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iter->cpu = -1;
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iter->second_pass = true;
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} else
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return NULL;
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#else
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return NULL;
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#endif
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}
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}
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return iter;
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}
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static void *timer_list_start(struct seq_file *file, loff_t *offset)
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{
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struct timer_list_iter *iter = file->private;
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if (!*offset)
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iter->now = ktime_to_ns(ktime_get());
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iter->cpu = -1;
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iter->second_pass = false;
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return move_iter(iter, *offset);
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}
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static void *timer_list_next(struct seq_file *file, void *v, loff_t *offset)
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{
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struct timer_list_iter *iter = file->private;
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++*offset;
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return move_iter(iter, 1);
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}
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static void timer_list_stop(struct seq_file *seq, void *v)
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{
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}
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static const struct seq_operations timer_list_sops = {
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.start = timer_list_start,
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.next = timer_list_next,
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.stop = timer_list_stop,
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.show = timer_list_show,
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};
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static int timer_list_open(struct inode *inode, struct file *filp)
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{
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return seq_open_private(filp, &timer_list_sops,
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sizeof(struct timer_list_iter));
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}
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static const struct file_operations timer_list_fops = {
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.open = timer_list_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = seq_release_private,
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};
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static int __init init_timer_list_procfs(void)
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{
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struct proc_dir_entry *pe;
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pe = proc_create("timer_list", 0444, NULL, &timer_list_fops);
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if (!pe)
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return -ENOMEM;
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return 0;
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}
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__initcall(init_timer_list_procfs);
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