From: Dan Williams <dan.j.williams@intel.com>
To: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
Ben Hutchings <ben@decadent.org.uk>,
Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH 0/2] fix devm_memremap_pages() mem hotplug locking
Date: Sun, 12 Feb 2017 17:35:00 -0800 [thread overview]
Message-ID: <CAPcyv4j0eC3=CPkP6NOMkTpcuik3Ln-D4cj6Nhz50H-srjkbAQ@mail.gmail.com> (raw)
In-Reply-To: <58A10B25.6030508@jp.fujitsu.com>
On Sun, Feb 12, 2017 at 5:25 PM, Masayoshi Mizuma
<m.mizuma@jp.fujitsu.com> wrote:
> Hi Dan,
>
> On Sun, 12 Feb 2017 14:34:11 -0800 Dan Williams wrote:
>>
>> Ben notes that commit f931ab479dd2 "mm: fix devm_memremap_pages crash,
>> use mem_hotplug_{begin, done}" is incomplete and broken. Writes to
>> mem_hotplug.active_writer need to be coordinated under the device
>> hotplug lock. Otherwise, we can potentially corrupt mem_hotplug.refcount
>> leading to soft lockups.
>
>
> I think mem_hotplug_{begin,done} is not suitable to exclude
> devm_memremap_pages()
> because it seems that memory hotplug is not related to this context.
> How about using pgmap_lock instead?
The problem with that switch is the race in
kernel_physical_mapping_init(), see commit f931ab479dd2. As far as I
can see we need all paths that call kernel_physical_mapping_init() to
agree on the same lock, and can't use a private lock in
devm_memremap_pages().
next prev parent reply other threads:[~2017-02-13 1:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-12 22:34 [PATCH 0/2] fix devm_memremap_pages() mem hotplug locking Dan Williams
2017-02-12 22:34 ` [PATCH 1/2] mm, devm_memremap_pages: hold device_hotplug lock over mem_hotplug_{begin, done} Dan Williams
2017-02-12 22:34 ` [PATCH 2/2] mm: validate device_hotplug is held for memory hotplug Dan Williams
2017-02-13 1:25 ` [PATCH 0/2] fix devm_memremap_pages() mem hotplug locking Masayoshi Mizuma
2017-02-13 1:35 ` Dan Williams [this message]
2017-02-15 0:24 ` Masayoshi Mizuma
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