Messages in this thread Patch in this message | | | From | Anna-Maria Behnsen <> | Subject | [PATCH v5 12/18] timer: Add get next timer interrupt functionality for remote CPUs | Date | Wed, 1 Mar 2023 15:17:38 +0100 |
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To prepare for the conversion of the NOHZ timer placement to a pull at expiry time model it's required to have functionality available getting the next timer interrupt on a remote CPU.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de> --- kernel/time/tick-internal.h | 8 +++++++ kernel/time/timer.c | 46 +++++++++++++++++++++++++++++++++---- 2 files changed, 49 insertions(+), 5 deletions(-)
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index 649f2b48e8f0..28471c8f8c9c 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -8,6 +8,11 @@ #include "timekeeping.h" #include "tick-sched.h" +struct timer_events { + u64 local; + u64 global; +}; + #ifdef CONFIG_GENERIC_CLOCKEVENTS # define TICK_DO_TIMER_NONE -1 @@ -164,6 +169,9 @@ static inline void timers_update_nohz(void) { } DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases); extern u64 get_next_timer_interrupt(unsigned long basej, u64 basem); +extern void fetch_next_timer_interrupt_remote(unsigned long basej, u64 basem, + struct timer_events *tevt, + unsigned int cpu); void timer_clear_idle(void); #define CLOCK_SET_WALL \ diff --git a/kernel/time/timer.c b/kernel/time/timer.c index dfc744545159..9daaef5d2f6f 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -221,11 +221,6 @@ struct timer_base { static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]); -struct timer_events { - u64 local; - u64 global; -}; - #ifdef CONFIG_NO_HZ_COMMON static DEFINE_STATIC_KEY_FALSE(timers_nohz_active); @@ -1984,6 +1979,47 @@ static unsigned long fetch_next_timer_interrupt(struct timer_base *base_local, return local_first ? nextevt_local : nextevt_global; } +/** + * fetch_next_timer_interrupt_remote + * @basej: base time jiffies + * @basem: base time clock monotonic + * @tevt: Pointer to the storage for the expiry values + * @cpu: Remote CPU + * + * Stores the next pending local and global timer expiry values in the + * struct pointed to by @tevt. If a queue is empty the corresponding + * field is set to KTIME_MAX. If local event expires before global + * event, global event is set to KTIME_MAX as well. + */ +void fetch_next_timer_interrupt_remote(unsigned long basej, u64 basem, + struct timer_events *tevt, + unsigned int cpu) +{ + struct timer_base *base_local, *base_global; + unsigned long flags; + + /* Preset local / global events */ + tevt->local = tevt->global = KTIME_MAX; + + /* + * Pretend that there is no timer pending if the cpu is offline. + * Possible pending timers will be migrated later to an active cpu. + */ + if (cpu_is_offline(cpu)) + return; + + base_local = per_cpu_ptr(&timer_bases[BASE_LOCAL], cpu); + base_global = per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu); + + raw_spin_lock_irqsave(&base_local->lock, flags); + raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING); + + fetch_next_timer_interrupt(base_local, base_global, basej, basem, tevt); + + raw_spin_unlock(&base_global->lock); + raw_spin_unlock_irqrestore(&base_local->lock, flags); +} + /* * Forward base clock is done only when @basej is past base->clk, otherwise * base-clk might be rewind. -- 2.30.2
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