linux-kernel - Re: [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate

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Message-ID: <alpine.LSU.2.21.2110271340180.3655@pobox.suse.cz>
Date:   Wed, 27 Oct 2021 13:42:38 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Ming Lei <ming.lei@...hat.com>
cc:     Petr Mladek <pmladek@...e.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>, tj@...nel.org,
        gregkh@...uxfoundation.org, akpm@...ux-foundation.org,
        minchan@...nel.org, jeyu@...nel.org, shuah@...nel.org,
        bvanassche@....org, dan.j.williams@...el.com, joe@...ches.com,
        tglx@...utronix.de, keescook@...omium.org, rostedt@...dmis.org,
        linux-spdx@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        live-patching@...r.kernel.org
Subject: Re: [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate

> > 
> > The livepatch code uses workqueue because the livepatch can be
> > disabled via sysfs interface. It obviously could not wait until
> > the sysfs interface is removed in the sysfs write() callback
> > that triggered the removal.
> 
> If klp_free_patch_* is moved into module_exit() and not let enable
> store() to kill kobjects, all kobjects can be deleted in module_exit(),
> then wait_for_completion(patch->finish) may be removed, also wq isn't
> required for the async cleanup.

It sounds like a nice cleanup. If we combine kobject_del() to prevent any 
show()/store() accesses and free everything later in module_exit(), it 
could work. If I am not missing something around how we maintain internal 
lists of live patches and their modules.

Thanks

Miroslav