ichsmb(4) and msleep()

[Conrad Meyer]

On Wed, Aug 28, 2019 at 6:35 AM Yuri Pankov <yuripv at yuripv.net> wrote:
>
> Warner Losh wrote:
> > What's the advantages of doing this instead of deferring attach until the
> > interrupts are running?
>
> None that I can think of, just going with what was suggested and seeing
> other drivers doing the same.  Could you please name a driver that
> defers attach until !cold?

I think pretty much all drivers attach when interrupts are enabled
(not the same as !cold)?  At least x86 enables interrupts on BSP at
SI_SUB_INTR, and DRIVER_MODULE drivers *load* at SI_SUB_DRIVERS, and
the INTR one is ordered before the other.  My skim read is that
drivers do not actually attach until SI_SUB_CONFIGURE.

I think the panic / test in sleepq_set_timeout_sbt is maybe overly
strong?  !cold indicates the entire autoconfigure process has
concluded.  But interrupts are available long before that.  Seems like
hardclock is started at ~SI_SUB_CLOCKS?  Which is admittedly after
DRIVERS, but still long before !cold.  I'm not sure what set of
interrupt/timer functionality is needed for sleepq, but likely that
condition can be relaxed.

If it cannot be relaxed enough for your driver, you could expand your
DRIVER_MODULE() into the expanded macro, replacing SI_SUB_DRIVERS with
a later stage.

Best,
Conrad