Messages in this thread | | | Date | Wed, 4 Oct 2023 14:39:32 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH printk] printk: flush consoles before checking progress |
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On Wed 2023-10-04 12:31:07, John Ogness wrote: > On 2023-10-02, Petr Mladek <pmladek@suse.com> wrote: > > I was about to push this patch and ran checkpatch.pl. It warned about > > > > WARNING: msleep < 20ms can sleep for up to 20ms; see Documentation/timers/timers-howto.rst > > #73: FILE: kernel/printk/printk.c:3782: > > + msleep(1); > > > > And indeed, Documentation/timers/timers-howto.rst says that msleep() > > might sleep longer that expected for <20ms delays. I guess that > > it is somehow related to jiffies, HZ, and load on the system. > > > > I think that we need to count jiffies here. > > Agreed. The @timeout_ms parameter should be respected. > > > Something like: > > > > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > > index db81b68d7f14..6ea500d95fd9 100644 > > --- a/kernel/printk/printk.c > > +++ b/kernel/printk/printk.c > > @@ -3772,24 +3773,19 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre > > console_srcu_read_unlock(cookie); > > > > if (diff != last_diff && reset_on_progress) > > - remaining = timeout_ms; > > + timeout_end = jiffies + timeout_jiffies; > > > > console_unlock(); > > > > /* Note: @diff is 0 if there are no usable consoles. */ > > - if (diff == 0 || remaining == 0) > > + if (diff == 0) > > break; > > > > - if (remaining < 0) { > > - /* no timeout limit */ > > - msleep(100); > > - } else if (remaining < 100) { > > - msleep(remaining); > > - remaining = 0; > > - } else { > > - msleep(100); > > - remaining -= 100; > > - } > > + /* Negative timeout means an infinite wait. */ > > + if (timeout_ms >= 0 && time_after_eq(jiffies, timeout_end)) > > + break; > > + > > + msleep(2000 / HZ); > > Is there really any advantage to this? I would just do msleep(1) and let > msleep round up. Everything else (tracking via jiffies) looks fine to me.
It was attempt to synchronize it with a scheduler tick. I saw it somewhere ;-) But you are right. Let's keep it simple and use msleep(1).
> > last_diff = diff; > > } > > > > And we should do this in a separate patch. It seems that sleeping > > is a bigger magic than I expected. > > Agreed.
Are you going to prepare them or should I?
Best Regards, Petr
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