Re: pci driver loads right after unload

[Max Gurtovoy]

Hi Greg/Bjorn,

On 1/2/2018 9:27 PM, Greg Kroah-Hartman wrote:
> On Tue, Jan 02, 2018 at 01:00:03PM -0600, Bjorn Helgaas wrote:
> > [+cc Greg, linux-kernel]
> >
> > Hi Max,
> >
> > Thanks for the report!
> >
> > On Tue, Jan 02, 2018 at 01:50:23AM +0200, Max Gurtovoy wrote:
> > > hi all,
> > > I encountered a strange phenomena using 2 different pci drivers
> > > (nvme and mlx5_core) since 4.15-rc1:
> > > when I try to unload the modules using "modprobe -r" cmd it calls
> > > the .probe function right after calling the .remove function and the
> > > module is not realy unloaded.
> > > I think there is some race condition because when I added a
> > > msleep(1000) after "pci_unregister_driver(&nvme_driver);" (in the
> > > nvme module testing, it also worked in the mlx5_core), the issue
> > > seems to dissapear.
> >
> > You say "since 4.15-rc1".  Does that mean it's a regression?  If so,
> > what's the most recent kernel that does not have this problem?  Worst
> > case, you could bisect to find where it broke.
> >
> > I don't see anything obvious in the drivers/pci changes between v4.14
> > and v4.15-rc1.  Module loading and driver binding is mostly driven by
> > the driver core and udev.  Maybe you could learn something with
> > "udevadm monitor" or by turning on the some of the debug in
> > lib/kobject_uevent.c?
>
>
> This should be resolved in 4.15-rc6, there was a regression in -rc1 in
> this area when dealing with uevents over netlink.
>
> Max, can you test -rc6 to verify if this is really fixed or not?

I've tested -rc6 and the issue doesn't repro.
I'll continue monitoring this scenario in -rc7.
Can you point to the commit that fixes the issue ? and I'll test the 
kernel with/without this patch.

> thanks,
>
> greg k-h

Cheers,
Max.