From: David Hildenbrand <david@redhat.com>
To: Rashmica <rashmica.g@gmail.com>, linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org,
xen-devel@lists.xenproject.org, devel@linuxdriverproject.org,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Len Brown <lenb@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>,
Michael Neuling <mikey@neuling.org>,
Balbir Singh <bsingharora@gmail.com>,
Kate Stewart <kstewart@linuxfoundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Philippe Ombredanne <pombredanne@nexb.com>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
Pavel Tatashin <pasha.tatashin@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>,
Dan Williams <dan.j.williams@intel.com>,
Oscar Salvador <osalvador@suse.de>,
YASUAKI ISHIMATSU <yasu.isimatu@gmail.com>,
Mathieu Malaterre <malat@debian.org>
Subject: Re: [PATCH RFCv2 3/6] mm/memory_hotplug: fix online/offline_pages called w.o. mem_hotplug_lock
Date: Mon, 17 Sep 2018 09:32:27 +0200 [thread overview]
Message-ID: <5f80ca56-9f34-4e6e-bc83-8f8b3c888163@redhat.com> (raw)
In-Reply-To: <70372ef5-e332-6c07-f08c-50f8808bde6d@gmail.com>
Am 03.09.18 um 02:36 schrieb Rashmica:
> Hi David,
>
>
> On 21/08/18 20:44, David Hildenbrand wrote:
>
>> There seem to be some problems as result of 30467e0b3be ("mm, hotplug:
>> fix concurrent memory hot-add deadlock"), which tried to fix a possible
>> lock inversion reported and discussed in [1] due to the two locks
>> a) device_lock()
>> b) mem_hotplug_lock
>>
>> While add_memory() first takes b), followed by a) during
>> bus_probe_device(), onlining of memory from user space first took b),
>> followed by a), exposing a possible deadlock.
>
> Do you mean "onlining of memory from user space first took a),
> followed by b)"?
Very right, thanks.
>
>> In [1], and it was decided to not make use of device_hotplug_lock, but
>> rather to enforce a locking order.
>>
>> The problems I spotted related to this:
>>
>> 1. Memory block device attributes: While .state first calls
>> mem_hotplug_begin() and the calls device_online() - which takes
>> device_lock() - .online does no longer call mem_hotplug_begin(), so
>> effectively calls online_pages() without mem_hotplug_lock.
>>
>> 2. device_online() should be called under device_hotplug_lock, however
>> onlining memory during add_memory() does not take care of that.
>>
>> In addition, I think there is also something wrong about the locking in
>>
>> 3. arch/powerpc/platforms/powernv/memtrace.c calls offline_pages()
>> without locks. This was introduced after 30467e0b3be. And skimming over
>> the code, I assume it could need some more care in regards to locking
>> (e.g. device_online() called without device_hotplug_lock - but I'll
>> not touch that for now).
>
> Can you mention that you fixed this in later patches?
Sure!
>
>
> The series looks good to me. Feel free to add my reviewed-by:
>
> Reviewed-by: Rashmica Gupta <rashmica.g@gmail.com>
>
Thanks, r-b only for this patch or all of the series?
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2018-09-17 7:32 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-21 10:44 [PATCH RFCv2 0/6] mm: online/offline_pages called w.o. mem_hotplug_lock David Hildenbrand
2018-08-21 10:44 ` [PATCH RFCv2 1/6] mm/memory_hotplug: make remove_memory() take the device_hotplug_lock David Hildenbrand
2018-08-30 19:35 ` Pasha Tatashin
2018-08-31 13:12 ` David Hildenbrand
2018-08-21 10:44 ` [PATCH RFCv2 2/6] mm/memory_hotplug: make add_memory() " David Hildenbrand
2018-08-30 19:36 ` Pasha Tatashin
2018-08-21 10:44 ` [PATCH RFCv2 3/6] mm/memory_hotplug: fix online/offline_pages called w.o. mem_hotplug_lock David Hildenbrand
2018-08-30 19:37 ` Pasha Tatashin
[not found] ` <70372ef5-e332-6c07-f08c-50f8808bde6d@gmail.com>
2018-09-17 7:32 ` David Hildenbrand [this message]
2018-09-25 1:26 ` Rashmica Gupta
2018-08-21 10:44 ` [PATCH RFCv2 4/6] powerpc/powernv: hold device_hotplug_lock when calling device_online() David Hildenbrand
2018-08-30 19:38 ` Pasha Tatashin
2018-08-21 10:44 ` [PATCH RFCv2 5/6] powerpc/powernv: hold device_hotplug_lock in memtrace_offline_pages() David Hildenbrand
2018-08-30 19:38 ` Pasha Tatashin
2018-08-21 10:44 ` [PATCH RFCv2 6/6] memory-hotplug.txt: Add some details about locking internals David Hildenbrand
2018-08-30 19:38 ` Pasha Tatashin
2018-08-30 12:31 ` [PATCH RFCv2 0/6] mm: online/offline_pages called w.o. mem_hotplug_lock David Hildenbrand
2018-08-30 15:54 ` Pasha Tatashin
2018-08-31 20:54 ` Oscar Salvador
2018-09-01 14:03 ` David Hildenbrand
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