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3ce74f1a85
tick_nohz_idle_got_tick() is called by cpuidle_reflect() within the idle loop with interrupts enabled. This function modifies the struct tick_sched's bitfield "got_idle_tick". However this bitfield is stored within the same mask as other bitfields that can be modified from interrupts. Fortunately so far it looks like the only race that can happen is while writing ->got_idle_tick to 0, an interrupt fires and writes the ->idle_active field to 0. It's then possible that the interrupted write to ->got_idle_tick writes back the old value of ->idle_active back to 1. However if that happens, the worst possible outcome is that the time spent between that interrupt and the upcoming call to tick_nohz_idle_exit() is accounted as idle, which is negligible quantity. Still all the bitfield writes within this struct tick_sched's shadow mask should be IRQ-safe. Therefore move this bitfield out to its own storage to avoid further suprises. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240225225508.11587-12-frederic@kernel.org
122 lines
3.9 KiB
C
122 lines
3.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _TICK_SCHED_H
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#define _TICK_SCHED_H
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#include <linux/hrtimer.h>
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enum tick_device_mode {
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TICKDEV_MODE_PERIODIC,
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TICKDEV_MODE_ONESHOT,
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};
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struct tick_device {
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struct clock_event_device *evtdev;
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enum tick_device_mode mode;
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};
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enum tick_nohz_mode {
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NOHZ_MODE_INACTIVE,
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NOHZ_MODE_LOWRES,
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NOHZ_MODE_HIGHRES,
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};
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/**
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* struct tick_sched - sched tick emulation and no idle tick control/stats
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*
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* @inidle: Indicator that the CPU is in the tick idle mode
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* @tick_stopped: Indicator that the idle tick has been stopped
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* @idle_active: Indicator that the CPU is actively in the tick idle mode;
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* it is reset during irq handling phases.
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* @do_timer_last: CPU was the last one doing do_timer before going idle
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* @got_idle_tick: Tick timer function has run with @inidle set
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* @stalled_jiffies: Number of stalled jiffies detected across ticks
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* @last_tick_jiffies: Value of jiffies seen on last tick
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* @sched_timer: hrtimer to schedule the periodic tick in high
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* resolution mode
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* @last_tick: Store the last tick expiry time when the tick
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* timer is modified for nohz sleeps. This is necessary
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* to resume the tick timer operation in the timeline
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* when the CPU returns from nohz sleep.
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* @next_tick: Next tick to be fired when in dynticks mode.
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* @idle_jiffies: jiffies at the entry to idle for idle time accounting
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* @idle_waketime: Time when the idle was interrupted
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* @idle_entrytime: Time when the idle call was entered
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* @nohz_mode: Mode - one state of tick_nohz_mode
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* @last_jiffies: Base jiffies snapshot when next event was last computed
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* @timer_expires_base: Base time clock monotonic for @timer_expires
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* @timer_expires: Anticipated timer expiration time (in case sched tick is stopped)
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* @next_timer: Expiry time of next expiring timer for debugging purpose only
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* @idle_expires: Next tick in idle, for debugging purpose only
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* @idle_calls: Total number of idle calls
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* @idle_sleeps: Number of idle calls, where the sched tick was stopped
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* @idle_exittime: Time when the idle state was left
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* @idle_sleeptime: Sum of the time slept in idle with sched tick stopped
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* @iowait_sleeptime: Sum of the time slept in idle with sched tick stopped, with IO outstanding
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* @tick_dep_mask: Tick dependency mask - is set, if someone needs the tick
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* @check_clocks: Notification mechanism about clocksource changes
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*/
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struct tick_sched {
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/* Common flags */
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unsigned int inidle : 1;
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unsigned int tick_stopped : 1;
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unsigned int idle_active : 1;
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unsigned int do_timer_last : 1;
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/* Tick handling: jiffies stall check */
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unsigned int stalled_jiffies;
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unsigned long last_tick_jiffies;
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/* Tick handling */
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struct hrtimer sched_timer;
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ktime_t last_tick;
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ktime_t next_tick;
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unsigned long idle_jiffies;
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ktime_t idle_waketime;
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unsigned int got_idle_tick;
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/* Idle entry */
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seqcount_t idle_sleeptime_seq;
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ktime_t idle_entrytime;
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/* Tick stop */
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enum tick_nohz_mode nohz_mode;
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unsigned long last_jiffies;
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u64 timer_expires_base;
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u64 timer_expires;
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u64 next_timer;
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ktime_t idle_expires;
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unsigned long idle_calls;
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unsigned long idle_sleeps;
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/* Idle exit */
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ktime_t idle_exittime;
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ktime_t idle_sleeptime;
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ktime_t iowait_sleeptime;
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/* Full dynticks handling */
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atomic_t tick_dep_mask;
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/* Clocksource changes */
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unsigned long check_clocks;
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};
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extern struct tick_sched *tick_get_tick_sched(int cpu);
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extern void tick_setup_sched_timer(int mode);
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#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
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extern void tick_cancel_sched_timer(int cpu);
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#else
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static inline void tick_cancel_sched_timer(int cpu) { }
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#endif
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#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
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extern int __tick_broadcast_oneshot_control(enum tick_broadcast_state state);
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#else
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static inline int
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__tick_broadcast_oneshot_control(enum tick_broadcast_state state)
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{
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return -EBUSY;
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}
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#endif
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#endif
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