linux-kernel - Re: [PATCH v1] ACPI / scan: Acquire device_hotplug_lock in acpi_scan

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Message-ID: <20190726084408.GK6142@dhcp22.suse.cz>
Date:   Fri, 26 Jul 2019 10:44:08 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-acpi@...r.kernel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>
Subject: Re: [PATCH v1] ACPI / scan: Acquire device_hotplug_lock in
 acpi_scan_init()

On Fri 26-07-19 10:36:42, David Hildenbrand wrote:
> On 26.07.19 10:31, Michal Hocko wrote:
[...]
> > Anyway, my dislike of the device_hotplug_lock persists. I would really
> > love to see it go rather than grow even more to the hotplug code. We
> > should be really striving for mem hotplug internal and ideally range
> > defined locking longterm. 
> 
> Yes, and that is a different story, because it will require major
> changes to all add_memory() users. (esp, due to the documented race
> conditions). Having that said, memory hotplug locking is not ideal yet.

I am really happy to hear that we are on the same page here. Do we have
any document (I am sorry but I am lacking behind recent development in
this area) that describes roadblocks to remove device_hotplug_lock?
-- 
Michal Hocko
SUSE Labs