Subject: Re: pci driver loads right after unload
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Bjorn Helgaas <helgaas@kernel.org>
CC: <linux-pci@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <13c000eb-5fbe-1787-54c0-d113500cf3db@mellanox.com>
 <20180102190003.GB6211@bhelgaas-glaptop.roam.corp.google.com>
 <20180102192721.GB10273@kroah.com>
From: Max Gurtovoy <maxg@mellanox.com>
Message-ID: <fb4bb470-c30e-c173-3267-99e283f79e02@mellanox.com>
Date: Wed, 3 Jan 2018 12:50:05 +0200
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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.