On Mon, Jan 23, 2023 at 06:18:26PM +0000, Matthew Wilcox wrote:
> On Mon, Jan 23, 2023 at 12:04:40PM -0600, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> >
> > Document the fact that CONFIG_BOOT_PRINTK_DELAY must be enabled for the
> > "boot_delay" kernel parameter to work. Also mention that "lpj=" may be
> > necessary.
> >
> > Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > ---
> > Documentation/admin-guide/kernel-parameters.txt | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 6cfa6e3996cf..b0b40b6a765c 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -480,8 +480,9 @@
> > See Documentation/block/cmdline-partition.rst
> >
> > boot_delay= Milliseconds to delay each printk during boot.
> > - Values larger than 10 seconds (10000) are changed to
> > - no delay (0).
> > + Enable CONFIG_BOOT_PRINTK_DELAY and also specify
> > + "lpj=". Boot_delay values larger than 10 seconds
> > + (10000) are changed to no delay (0).
>
> That's counterintuitive. I'd understand clamping it to 10 seconds,
> but not setting it to zero.
I'm not opposed to setting it to 10 sec instead of 0, but that came
from bfe8df3d314b ("slow down printk during boot"); added Randy in
case he wants to comment.
> Also, there are two ways of reading this. One is that by specifying
> boot_delay=, lpj= is set to a sane value. The other (intended?) is
> that in order to use this option, you must also specify lpj=.
Maybe this is better?
boot_delay= Milliseconds to delay each printk during boot.
- Values larger than 10 seconds (10000) are changed to
- no delay (0).
+ Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
+ and you may also have to specify "lpj=". Boot_delay
+ values larger than 10 seconds (10000) are changed
+ to no delay (0).
Format: integer
bootconfig [KNL]
