From da65f29dada7f7cbbf0d6375b88a0316f5f7d6f5 Mon Sep 17 00:00:00 2001 From: Anna-Maria Behnsen Date: Fri, 1 Dec 2023 10:26:34 +0100 Subject: timers: Fix nextevt calculation when no timers are pending When no timer is queued into an empty timer base, the next_expiry will not be updated. It was originally calculated as base->clk + NEXT_TIMER_MAX_DELTA When the timer base stays empty long enough (> NEXT_TIMER_MAX_DELTA), the next_expiry value of the empty base suggests that there is a timer pending soon. This might be more a kind of a theoretical problem, but the fix doesn't hurt. Use only base->next_expiry value as nextevt when timers are pending. Otherwise nextevt will be jiffies + NEXT_TIMER_MAX_DELTA. As all information is in place, update base->next_expiry value of the empty timer base as well. Signed-off-by: Anna-Maria Behnsen Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lore.kernel.org/r/20231201092654.34614-13-anna-maria@linutronix.de --- kernel/time/timer.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'kernel/time/timer.c') diff --git a/kernel/time/timer.c b/kernel/time/timer.c index cf51655add64..352b161113cd 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1922,8 +1922,8 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expires) u64 get_next_timer_interrupt(unsigned long basej, u64 basem) { struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]); + unsigned long nextevt = basej + NEXT_TIMER_MAX_DELTA; u64 expires = KTIME_MAX; - unsigned long nextevt; bool was_idle; /* @@ -1936,7 +1936,6 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) raw_spin_lock(&base->lock); if (base->next_expiry_recalc) next_expiry_recalc(base); - nextevt = base->next_expiry; /* * We have a fresh next event. Check whether we can forward the @@ -1945,10 +1944,20 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) __forward_timer_base(base, basej); if (base->timers_pending) { + nextevt = base->next_expiry; + /* If we missed a tick already, force 0 delta */ if (time_before(nextevt, basej)) nextevt = basej; expires = basem + (u64)(nextevt - basej) * TICK_NSEC; + } else { + /* + * Move next_expiry for the empty base into the future to + * prevent a unnecessary raise of the timer softirq when the + * next_expiry value will be reached even if there is no timer + * pending. + */ + base->next_expiry = nextevt; } /* -- cgit