linux-kernel - Re: [PATCH 1/2] zram: fix crashes due to use of cpu hotplug multistate

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Message-ID: <nycvar.YFH.7.76.2104081015340.18270@cbobk.fhfr.pm>
Date:   Thu, 8 Apr 2021 10:35:17 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Greg KH <gregkh@...uxfoundation.org>
cc:     Thomas Gleixner <tglx@...utronix.de>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Minchan Kim <minchan@...nel.org>, keescook@...omium.org,
        dhowells@...hat.com, hch@...radead.org, mbenes@...e.com,
        ngupta@...are.org, sergey.senozhatsky.work@...il.com,
        Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] zram: fix crashes due to use of cpu hotplug
 multistate

On Thu, 8 Apr 2021, Greg KH wrote:

> > If there is a driver/subsystem code that can't handle the reverse 
> > operation to modprobe, it clearly can't handle error handling during 
> > modprobe (which, one would hope, is supported), and should be fixed.
> 
> Huh?  No, that's not the issue here, it's the issue of different
> userspace code paths into the module at the same time that it is trying
> to be unloaded.  That has nothing to do with loading the module the
> first time as userspace is not touching those apis yet.

So do you claim that once the first (out of possibly many) 
userspace-visible sysfs entry has been created during module insertion and 
made available to userspace, there is never going to be rollback happening 
that'd be removing that first sysfs entry again?

Thanks,

-- 
Jiri Kosina
SUSE Labs