Re: [PATCH RFC 2/4] printk: deprecate boot_delay in favour of printk_delay

[Petr Mladek]

On Sun 2026-06-14 12:45:44, Andrew Murray wrote:
> On Mon, 8 Jun 2026 at 15:07, Petr Mladek <pmladek@xxxxxxxx> wrote:
> >
> > On Mon 2026-06-01 00:17:38, Andrew Murray wrote:
> > > The boot_delay (BOOT_PRINTK_DELAY) kernel parameter and printk_delay sysctl
> > > are two distinct mechanisms for providing similar functionality which add a
> > > delay prior to each printed printk message.
> > >
> > > boot_delay provides a kernel parameter for delaying printk output from
> > > kernel start through to boot (SYSTEM_RUNNING), whereas printk_delay is
> > > configurable only via sysctl and thus is only used post boot.
> > >
> > > Let's deprecate the boot_delay feature in favour of printk_delay. In order
> > > to preserve functionality, we'll also extend printk_delay such that it can
> > > additionally configured via a kernel parameter.
> >
> > > --- a/kernel/printk/printk.c
> > > +++ b/kernel/printk/printk.c
> > > @@ -1339,11 +1327,34 @@ static void boot_delay_msec(int level)
> > >       }
> > >  }
> > >  #else
> > > -static inline void boot_delay_msec(int level)
> > > +static inline void __init printk_delay_calculate(void)
> > > +{
> > > +}
> > > +
> > > +static inline void early_boot_delay_msec(void)
> > >  {
> >
> > It would be nice to print a warning that the early boot delay
> > does not work, something like:
> >
> >         pr_warn_once("Early boot delay does not work without CONFIG_GENERIC_CALIBRATE_DELAY enabled.\n");
> >
> > >  }
> > >  #endif
> > >
> > > +static int __init printk_delay_setup(char *str)
> > > +{
> > > +     get_option(&str, &printk_delay_msec);
> > > +     if (printk_delay_msec > 10 * 1000)
> > > +             printk_delay_msec = 0;
> >
> > Sashiko AI warns that this code accepts negative values.
> > It might cause long delays, see
> > https://sashiko.dev/#/patchset/20260601-deprecate_boot_delay-v1-0-c34c187142a6%40thegoodpenguin.co.uk
> >
> > The problem has already been there even before. But it would be nice
> > to fix it.
> 
> Thanks for pointing out Sashiko, I hadn't seen its review on my
> patches. Are authors expected to get emails from it, as I didn't?

Sashiko is able to send mails but it is opt-in.

It might create too much noise because it has false positives, it
keeps reporting minor or nice-to-fix problems which will "never"
get fixed. Also it is not predictable so that you could not reliably
check the patchset before sending.

Anyway, I thought about enabling this for printk-related patches
because Sashiko also gives a lot of useful feedback. And it is easier
to discuss it as reply to a mail. But AFAIK, it can be done only
per-mailing list. And printk does not have any dedicated mailing list.

So, I "always" search for the feedback at https://sashiko.dev/

Best Regards,
Petr