Re: [bisected] Re: Module removal-related regression?

Jakub Kicinski
2017-09-10T18:39:42Z

On Sun, 10 Sep 2017 11:12:17 -0700, Dmitry Torokhov wrote:
> On September 10, 2017 11:00:10 AM PDT, Jakub Kicinski <kubakici@wp.pl> wrote:
> >On Sun, 10 Sep 2017 09:21:11 -0700, Dmitry Torokhov wrote:
> >> On Sun, Sep 10, 2017 at 12:03:38AM +0200, Jakub Kicinski wrote:
> >> > On Sat, 09 Sep 2017 13:59:25 -0700, Dmitry Torokhov wrote:
> >> > > On September 9, 2017 1:17:26 PM PDT, Jakub Kicinski
> ><kubakici@wp.pl> wrote:
> >> > > >On Sat, 9 Sep 2017 12:55:51 -0700, Dmitry Torokhov wrote:
> >> > > >> On Sat, Sep 9, 2017 at 12:27 PM, Jakub Kicinski
> ><kubakici@wp.pl>
> >> > > >wrote:
> >> > > >> > On Sat, 9 Sep 2017 19:41:21 +0200, Jakub Kicinski wrote:
> >
> >> > > >> >> Hi!
> >> > > >> >>
> >> > > >> >> I'm having trouble with modules on linux/master. rmmod
> >succeeds
> >> > > >but the
> >> > > >> >> module is still loaded and the refcount goes to 1:
> >> > > >> >>
> >> > > >> >> #rmmod nfp; insmod ./src/nfp.ko nfp_pf_netdev=0 ; \
> >> > > >> >> /opt/netronome/bin/nfp-hwinfo -n 2 assembly.partno \
> >> > > >> >> lsmod | grep nfp; \
> >> > > >> >> rmmod nfp; \
> >> > > >> >> lsmod | grep nfp
> >> > > >> >> nfp 249856 0
> >> > > >> >> nfp 200704 1
> >> > > >> >>
> >> > > >> >> If I rmmod again the module will be actually unloaded. The
> >user
> >> > > >space
> >> > > >> >> is mostly Ubuntu 14.04. Has anyone seen this? I'm trying
> >to
> >> > > >bisect
> >> > > >> >> now...
> >> > > >> >
> >> > > >> > Got 'em!
> >> > > >> >
> >> > > >> > commit 1455cf8dbfd06aa7651dcfccbadb7a093944ca65 (HEAD,
> >> > > >refs/bisect/bad)
> >> > > >> > Author: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> >> > > >> > Date: Wed Jul 19 17:24:30 2017 -0700
> >> > > >> >
> >> > > >> > driver core: emit uevents when device is bound to a
> >driver
> >> > > >>
> >> > > >> Does it happen with all modules or only nfp one?
> >> > > >>
> >> > > >> It seems to work here:
> >> > > >>
> >> > > >> dtor@dtor-glaptop3:~ $ lsmod | grep psmouse
> >> > > >> psmouse 135168 0
> >> > > >> dtor@dtor-glaptop3:~ $ sudo rmmod psmouse
> >> > > >> dtor@dtor-glaptop3:~ $ lsmod | grep psmouse
> >> > > >> dtor@dtor-glaptop3:~ $ sudo modprobe psmouse
> >> > > >
> >> > > >It looks like the driver is actually reloaded. The driver used
> >to
> >> > > >return EPROBE_DEFER, but I think it doesn't any more (rebuilding
> >the
> >> > > >kernel to test that right now).
> >> > > >
> >> > > >Could the uevent on unbind tickle Ubuntu 14.04's udev or somehow
> >> > > >else cause the driver to be loaded again?
> >> > >
> >> > > It depends on how silly the udev rules are, but yes, this can
> >definitely happen.
> >> >
> >> > I confirmed the driver doesn't use EPROBE_DEFER any more:
> >> >
> >> > $ grep -nrI EPROBE_DEFER drivers/net/ethernet/netronome/
> >> > $
> >>
> >> Not sure why you bring the deferrals here, they have nothing to do
> >with
> >> module removal. Also, deferrals are rarely issued by the leaf driver,
> >and
> >> more often by providers of resources (GPIO, regulator, interrupt,
> >etc).
> >
> >Yes, it's unusual, but this driver used to do it. Which is exactly why
> >I brought it up. Turns out it was irrelevant :)
> >
> >> > I tested without any udev rules in /etc/udev/, just the standard
> >distro
> >> > ones. Same thing.
> >>
> >> Right, so this is the default udev rule:
> >>
> >> /lib/udev/rules.d/80-drivers.rules:
> >>
> >> # do not edit this file, it will be overwritten on update
> >>
> >> ACTION=="remove", GOTO="drivers_end"
> >>
> >> ENV{MODALIAS}=="?*", RUN{builtin}="kmod load $env{MODALIAS}"
> >> SUBSYSTEM=="tifm", ENV{TIFM_CARD_TYPE}=="SD", RUN{builtin}="kmod load
> >tifm_sd"
> >> SUBSYSTEM=="tifm", ENV{TIFM_CARD_TYPE}=="MS", RUN{builtin}="kmod load
> >tifm_ms"
> >> SUBSYSTEM=="memstick", RUN{builtin}="kmod load ms_block mspro_block"
> >> SUBSYSTEM=="i2o", RUN{builtin}="kmod load i2o_block"
> >> SUBSYSTEM=="module", KERNEL=="parport_pc", RUN{builtin}="kmod load
> >ppdev"
> >> SUBSYSTEM=="serio", ENV{MODALIAS}=="?*", RUN{builtin}="kmod load
> >$env{MODALIAS}"
> >> SUBSYSTEM=="graphics", RUN{builtin}="kmod load fbcon"
> >> KERNEL=="mtd*ro", ENV{MTD_FTL}=="smartmedia", RUN{builtin}="kmod load
> >sm_ftl"
> >>
> >> LABEL="drivers_end"
> >>
> >> So udev (and systemd) want to load kernel module on any action
> >besides
> >> device removal. Shortsighted decision I'd say. I'll send a patch to
> >> systemd, in the mean time you can simply adjust your local rule to
> >read
> >>
> >> ACTION!="add", GOTO="drivers_end"
> >
> >Mm. That is a silly thing. You will break a lot of setups, though.
>
> I think the priority it to have module loading working properly, and
> for most users once module is loaded it stays loaded. Unloading is
> mostly for developers.
>
> Luckily newer systemd versions drop events they do not recognize, so
> exposure is even smaller.

Could you point me to where that's done?