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Date: Sun, 12 Feb 2017 17:35:00 -0800 From: Dan Williams <dan.j.williams@...el.com> To: Masayoshi Mizuma <m.mizuma@...fujitsu.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Michal Hocko <mhocko@...e.com>, "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "stable@...r.kernel.org" <stable@...r.kernel.org>, Ben Hutchings <ben@...adent.org.uk>, Vlastimil Babka <vbabka@...e.cz> Subject: Re: [PATCH 0/2] fix devm_memremap_pages() mem hotplug locking On Sun, Feb 12, 2017 at 5:25 PM, Masayoshi Mizuma <m.mizuma@...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().
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