Setting the realtime clock triggers an IPI to all CPUs to reprogram
the clock event device.
However, only realtime and TAI clocks have their offsets updated
(and therefore potentially require a reprogram).
Instead of sending an IPI unconditionally, check each per CPU hrtimer base
whether it has active timers in the CLOCK_REALTIME and CLOCK_TAI bases. If
that's not the case, update the realtime and TAI base offsets remotely and
skip the IPI. This ensures that any subsequently armed timers on
CLOCK_REALTIME and CLOCK_TAI are evaluated with the correct offsets.
Signed-off-by: Marcelo Tosatti <mtosa...@redhat.com>
---
v4:
- Drop unused code (Thomas).
v3:
- Nicer changelog (Thomas).
- Code style fixes (Thomas).
- Compilation warning with CONFIG_HIGH_RES_TIMERS=n (Thomas).
- Shrink preemption disabled section (Thomas).
v2:
- Only REALTIME and TAI bases are affected by offset-to-monotonic changes
(Thomas).
- Don't special case nohz_full CPUs (Thomas).
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 5c9d968187ae..e228c0a0c98f 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -871,6 +871,19 @@ static void hrtimer_reprogram(struct hrtimer *timer, bool
reprogram)
tick_program_event(expires, 1);
}
+#define CLOCK_SET_BASES ((1U << HRTIMER_BASE_REALTIME) | \
+ (1U << HRTIMER_BASE_REALTIME_SOFT) | \
+ (1U << HRTIMER_BASE_TAI) | \
+ (1U << HRTIMER_BASE_TAI_SOFT))
+
+static bool need_reprogram_timer(struct hrtimer_cpu_base *cpu_base)
+{
+ if (cpu_base->softirq_activated)
+ return true;
+
+ return (cpu_base->active_bases & CLOCK_SET_BASES) != 0;
+}
+
/*
* Clock realtime was set
*
@@ -885,8 +898,32 @@ static void hrtimer_reprogram(struct hrtimer *timer, bool
reprogram)
void clock_was_set(void)
{
#ifdef CONFIG_HIGH_RES_TIMERS
- /* Retrigger the CPU local events everywhere */
- on_each_cpu(retrigger_next_event, NULL, 1);
+ cpumask_var_t mask;
+ int cpu;
+
+ if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) {
+ on_each_cpu(retrigger_next_event, NULL, 1);
+ goto set_timerfd;
+ }
+
+ /* Avoid interrupting CPUs if possible */
+ cpus_read_lock();
+ for_each_online_cpu(cpu) {
+ unsigned long flags;
+ struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases,
cpu);
+
+ raw_spin_lock_irqsave(&cpu_base->lock, flags);
+ if (need_reprogram_timer(cpu_base))
+ cpumask_set_cpu(cpu, mask);
+ raw_spin_unlock_irqrestore(&cpu_base->lock, flags);
+ }
+
+ preempt_disable();
+ smp_call_function_many(mask, retrigger_next_event, NULL, 1);
+ preempt_enable();
+ cpus_read_unlock();
+ free_cpumask_var(mask);
+set_timerfd:
#endif
timerfd_clock_was_set();
}
