From 8c3b5e6ec0fee18bc2ce38d1dfe913413205f908 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 13 Jul 2021 15:39:48 +0200 Subject: hrtimer: Ensure timerfd notification for HIGHRES=n If high resolution timers are disabled the timerfd notification about a clock was set event is not happening for all cases which use clock_was_set_delayed() because that's a NOP for HIGHRES=n, which is wrong. Make clock_was_set_delayed() unconditially available to fix that. Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20210713135158.196661266@linutronix.de --- include/linux/hrtimer.h | 5 ----- 1 file changed, 5 deletions(-) (limited to 'include/linux/hrtimer.h') diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index bb5e7b0a4274..77295af72426 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -318,16 +318,12 @@ struct clock_event_device; extern void hrtimer_interrupt(struct clock_event_device *dev); -extern void clock_was_set_delayed(void); - extern unsigned int hrtimer_resolution; #else #define hrtimer_resolution (unsigned int)LOW_RES_NSEC -static inline void clock_was_set_delayed(void) { } - #endif static inline ktime_t @@ -351,7 +347,6 @@ hrtimer_expires_remaining_adjusted(const struct hrtimer *timer) timer->base->get_time()); } -extern void clock_was_set(void); #ifdef CONFIG_TIMERFD extern void timerfd_clock_was_set(void); #else -- cgit v1.2.3-71-gd317 From 66f7b0c8aadd2785fc29f2c71477ebc16f4e38cc Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 13 Jul 2021 15:39:50 +0200 Subject: timerfd: Provide timerfd_resume() Resuming timekeeping is a clock-was-set event and uses the clock-was-set notification mechanism. This is in the way of making the clock-was-set update for hrtimers selective so unnecessary IPIs are avoided when a CPU base does not have timers queued which are affected by the clock setting. Provide a seperate timerfd_resume() interface so the resume logic and the clock-was-set mechanism can be distangled in the core code. Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20210713135158.395287410@linutronix.de --- fs/timerfd.c | 16 ++++++++++++++++ include/linux/hrtimer.h | 2 ++ 2 files changed, 18 insertions(+) (limited to 'include/linux/hrtimer.h') diff --git a/fs/timerfd.c b/fs/timerfd.c index c5509d2448e3..e9c96a0c79f1 100644 --- a/fs/timerfd.c +++ b/fs/timerfd.c @@ -115,6 +115,22 @@ void timerfd_clock_was_set(void) rcu_read_unlock(); } +static void timerfd_resume_work(struct work_struct *work) +{ + timerfd_clock_was_set(); +} + +static DECLARE_WORK(timerfd_work, timerfd_resume_work); + +/* + * Invoked from timekeeping_resume(). Defer the actual update to work so + * timerfd_clock_was_set() runs in task context. + */ +void timerfd_resume(void) +{ + schedule_work(&timerfd_work); +} + static void __timerfd_remove_cancel(struct timerfd_ctx *ctx) { if (ctx->might_cancel) { diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 77295af72426..253c6e25f331 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -349,8 +349,10 @@ hrtimer_expires_remaining_adjusted(const struct hrtimer *timer) #ifdef CONFIG_TIMERFD extern void timerfd_clock_was_set(void); +extern void timerfd_resume(void); #else static inline void timerfd_clock_was_set(void) { } +static inline void timerfd_resume(void) { } #endif extern void hrtimers_resume(void); -- cgit v1.2.3-71-gd317 From a761a67f591a8c7476c30bb20ed0f09fdfb1a704 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 13 Jul 2021 15:39:51 +0200 Subject: timekeeping: Distangle resume and clock-was-set events Resuming timekeeping is a clock-was-set event and uses the clock-was-set notification mechanism. This is in the way of making the clock-was-set update for hrtimers selective so unnecessary IPIs are avoided when a CPU base does not have timers queued which are affected by the clock setting. Distangle it by invoking hrtimer_resume() on each unfreezing CPU and invoke the new timerfd_resume() function from timekeeping_resume() which is the only place where this is needed. Rename hrtimer_resume() to hrtimer_resume_local() to reflect the change. With this the clock_was_set*() functions are not longer required to IPI all CPUs unconditionally and can get some smarts to avoid them. Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20210713135158.488853478@linutronix.de --- include/linux/hrtimer.h | 1 - kernel/time/hrtimer.c | 15 ++++++--------- kernel/time/tick-common.c | 7 +++++++ kernel/time/tick-internal.h | 2 ++ kernel/time/timekeeping.c | 4 +++- 5 files changed, 18 insertions(+), 11 deletions(-) (limited to 'include/linux/hrtimer.h') diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 253c6e25f331..0ee140176f10 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -354,7 +354,6 @@ extern void timerfd_resume(void); static inline void timerfd_clock_was_set(void) { } static inline void timerfd_resume(void) { } #endif -extern void hrtimers_resume(void); DECLARE_PER_CPU(struct tick_device, tick_cpu_device); diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 214fd65a9597..68e56f0ecb09 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -900,8 +900,8 @@ static void clock_was_set_work(struct work_struct *work) static DECLARE_WORK(hrtimer_work, clock_was_set_work); /* - * Called from timekeeping and resume code to reprogram the hrtimer - * interrupt device on all cpus and to notify timerfd. + * Called from timekeeping code to reprogram the hrtimer interrupt device + * on all cpus and to notify timerfd. */ void clock_was_set_delayed(void) { @@ -909,18 +909,15 @@ void clock_was_set_delayed(void) } /* - * During resume we might have to reprogram the high resolution timer - * interrupt on all online CPUs. However, all other CPUs will be - * stopped with IRQs interrupts disabled so the clock_was_set() call - * must be deferred. + * Called during resume either directly from via timekeeping_resume() + * or in the case of s2idle from tick_unfreeze() to ensure that the + * hrtimers are up to date. */ -void hrtimers_resume(void) +void hrtimers_resume_local(void) { lockdep_assert_irqs_disabled(); /* Retrigger on the local CPU */ retrigger_next_event(NULL); - /* And schedule a retrigger for all others */ - clock_was_set_delayed(); } /* diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index d663249652ef..46789356f856 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -470,6 +470,13 @@ void tick_resume_local(void) else tick_resume_oneshot(); } + + /* + * Ensure that hrtimers are up to date and the clockevents device + * is reprogrammed correctly when high resolution timers are + * enabled. + */ + hrtimers_resume_local(); } /** diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index cd610faa2523..22de98cc6dd8 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -168,3 +168,5 @@ void timer_clear_idle(void); void clock_was_set(void); void clock_was_set_delayed(void); + +void hrtimers_resume_local(void); diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 8a364aa9881a..c8a9b9e54c9d 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1810,8 +1810,10 @@ void timekeeping_resume(void) touch_softlockup_watchdog(); + /* Resume the clockevent device(s) and hrtimers */ tick_resume(); - hrtimers_resume(); + /* Notify timerfd as resume is equivalent to clock_was_set() */ + timerfd_resume(); } int timekeeping_suspend(void) -- cgit v1.2.3-71-gd317