Re: infinite loop in read_hpet from ktime_get_boot_fast_ns

[Jason A. Donenfeld]

On Thu, Jun 13, 2019 at 6:26 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> That does not make sense. The coarse time getters use
> tk->tkr_mono.base. base is updated every tick (or if the machine is
> completely idle right when the first CPU wakes up again).

Sense or not, it seems to be happening, at least on 5.2-rc4:

int __init mod_init(void)
{
      for (;;) {
              pr_err("%llu %llu %llu\n", get_jiffies_64(),
ktime_get_coarse_boottime(), local_clock());
              msleep(200);
      }
      return 0;
}

[    0.308166] wireguard: 4294892358 270211253 308165785
[    0.512931] wireguard: 4294892410 270211253 512926052
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[    1.760963] wireguard: 4294892722 1270211253 1760957241
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[    4.464943] wireguard: 4294893398 4270211253 4464938724
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[    5.712963] wireguard: 4294893710 5270211253 5712957452
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[    6.128959] wireguard: 4294893814 5270211253 6128954684
[    6.336968] wireguard: 4294893866 6270211253 6336962979
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[    6.752963] wireguard: 4294893970 6270211253 6752958001
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[    7.376936] wireguard: 4294894126 7270211253 7376931429
[    7.585022] wireguard: 4294894178 7270211253 7585016996
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[    8.000953] wireguard: 4294894282 7270211253 8000947668
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[    9.456968] wireguard: 4294894646 9270211253 9456963019
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[    9.872935] wireguard: 4294894750 9270211253 9872929704