Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH] hrtimer: avoid retrigger_next_event IPI | Date | Sat, 10 Apr 2021 09:53:13 +0200 |
| |
On Fri, Apr 09 2021 at 13:51, Marcelo Tosatti wrote: > On Fri, Apr 09, 2021 at 04:15:13PM +0200, Thomas Gleixner wrote: >> On Wed, Apr 07 2021 at 10:53, Marcelo Tosatti wrote: >> ---> fail because that newly started timer is on the old offset. > > CPU0 CPU1 > > > clock_was_set() > Case-1: CPU-1 grabs base->lock before CPU-0: > CPU-0 sees active_mask[CPU1] and IPIs. > > base = lock_hrtimer_base(timer, &flags); > if (__hrtimer_start_range_ns(timer, tim, ... > hrtimer_reprogram(timer, true); > > unlock_hrtimer_base(timer, &flags); > > > raw_spin_lock_irqsave(&cpu_base->lock, flags); > if (need_reprogram_timer(cpu_base)) > cpumask_set_cpu(cpu, mask); > else > hrtimer_update_base(cpu_base); > raw_spin_unlock_irqrestore(&cpu_base->lock, flags); > > Case-2: CPU-1 grabs base->lock after CPU-0: > CPU-0 will have updated the offsets remotely. > > base = lock_hrtimer_base(timer, &flags); > if (__hrtimer_start_range_ns(timer, tim, ... > hrtimer_reprogram(timer, true); > > unlock_hrtimer_base(timer, &flags); > > > No?
Yeah, you're right. I misread the loop logic.
Can we please make that unconditional independent of nohz full. There is no reason to special case it.
Thanks,
tglx
| |