Re: [ANNOUNCE] kmod 30

[Lucas De Marchi]

On Fri, Jul 01, 2022 at 10:49:10AM -0700, Luis Chamberlain wrote:
> On Thu, Jun 30, 2022 at 03:33:23PM -0700, Lucas De Marchi wrote:
> > On Thu, Jun 30, 2022 at 03:09:32PM -0700, Luis Chamberlain wrote:
> > > Sorry for the super late review, I was swamped. OK so the only issue
> > > I can think of is that rmmod *used* to support the kernel wait support
> > > with $(rmmod --wait) so wouldn't this be odd?
> >
> > any reason not to use modprobe -r?
>
> I was referring to old scripts which may have used $(rmmod --wait) before.
> But since support for that was ripped, then yeah I can see that should
> not be an issue.
>
> However I can think of *one* issue, did we ever support `modprobe--wait`?

no

> Because the way fstests / blktests would implement this feature
> detection is with something like this now:
>
> _has_modprobe_patient()
> {
> 	modprobe --help >& /dev/null || return 1
> 	modprobe --help | grep -q -1 "remove-patiently" || return 1
> 	return 0
> }

the grep would need to be changed to something like "-w, --wait"

> > > It is why I had gone with:
> > >
> > > -p | --remove-patiently   patiently removes the module
> > > -t | --timeout            timeout in ms to remove the module
> > >
> > > You would know better though.
> > >
> > > Also just curious, is it really terrible to just support waiting
> > > forever?
> >
> > is there a use case for that? If we are trying to cover some races, I
> > imagine a small timeout would be sufficient. Also notice that if the
> > timeout is too big, so will be the interval between the retries.  On
> > your v2 I had suggested polling the refcnt so we would get notificed
> > on changes, but as you also noticed, that didn't work very well.  So I
> > went back to a time-based retry solution.
> >
> > if there is a use-case, should we cap the interval between retries?
>
> I really can't think of a use case except for catching glaring
> unexpected bugs in test suites where the kernel developer would
> really like to know something really bad happened, but even then
> a timeout is likely desirable.

yeah... if developer wants to possibly wait for a long time, `--wait -1`
is available to wait for years.

> So just a heads up the timeout I'll use for fstests / blktests will be
> of 100 seconds.

yeah... 100 seconds still make more sense than -1 IMO


Lucas De Marchi

> Thanks for this work!
>
>  Luis