linux-kernel - Re: infinite loop in read_hpet from ktime_get_boot_fast

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Message-ID: <CAHmME9q1ihF617=Gjw9k9BK7OC9Ghnzfnfi6LfvJ8DG+vrQOqA@mail.gmail.com>
Date:   Thu, 13 Jun 2019 18:34:22 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Clemens Ladisch <clemens@...isch.de>,
        Sultan Alsawaf <sultan@...neltoast.com>,
        Waiman Long <longman@...hat.com>, X86 ML <x86@...nel.org>
Subject: Re: infinite loop in read_hpet from ktime_get_boot_fast_ns

On Thu, Jun 13, 2019 at 6:26 PM Thomas Gleixner <tglx@...utronix.de> 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;
}

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