linux-kernel - Re: [PATCH RFC 1/2] drivers/base: export lock_device_hotplug/unlock_device

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Date:   Fri, 17 Aug 2018 13:28:50 +0200
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Paul Mackerras <paulus@...ba.org>, linux-s390@...r.kernel.org,
        sthemmin@...rosoft.com, Pavel Tatashin <pasha.tatashin@...cle.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        David Rientjes <rientjes@...gle.com>,
        xen-devel@...ts.xenproject.org, Len Brown <lenb@...nel.org>,
        haiyangz@...rosoft.com, Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>, osalvador@...e.de,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        devel@...uxdriverproject.org,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH RFC 1/2] drivers/base: export
 lock_device_hotplug/unlock_device_hotplug

On Fri, Aug 17, 2018 at 01:04:58PM +0200, David Hildenbrand wrote:
> >> If there are no objections, I'll go into that direction. But I'll wait
> >> for more comments regarding the general concept first.
> > 
> > It is the middle of the merge window, and maintainers are really busy
> > right now.  I doubt you will get many review comments just yet...
> > 
> 
> This has been broken since 2015, so I guess it can wait a bit :)

I hope you figured out what needs to be locked why. Your patch description
seems to be "only" about locking order ;)

I tried to figure out and document that partially with 55adc1d05dca ("mm:
add private lock to serialize memory hotplug operations"), and that wasn't
easy to figure out. I was especially concerned about sprinkling
lock/unlock_device_hotplug() calls, which has the potential to make it the
next BKL thing.