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Date: Mon, 13 Feb 2017 10:25:57 +0900 From: Masayoshi Mizuma <m.mizuma@...fujitsu.com> To: Dan Williams <dan.j.williams@...el.com>, <akpm@...ux-foundation.org> CC: Michal Hocko <mhocko@...e.com>, <linux-nvdimm@...ts.01.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, <linux-kernel@...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 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? Like this: diff --git a/kernel/memremap.c b/kernel/memremap.c index 9ecedc2..e9b9cfa 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -246,9 +246,9 @@ static void devm_memremap_pages_release(struct device *dev, void *data) /* pages are dead and unused, undo the arch mapping */ align_start = res->start & ~(SECTION_SIZE - 1); align_size = ALIGN(resource_size(res), SECTION_SIZE); - mem_hotplug_begin(); + mutex_lock(&pgmap_lock); arch_remove_memory(align_start, align_size); - mem_hotplug_done(); + mutex_unlock(&pgmap_lock); untrack_pfn(NULL, PHYS_PFN(align_start), align_size); pgmap_radix_release(res); dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc, @@ -360,9 +360,9 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, if (error) goto err_pfn_remap; - mem_hotplug_begin(); + mutex_lock(&pgmap_lock); error = arch_add_memory(nid, align_start, align_size, true); - mem_hotplug_done(); + mutex_unlock(&pgmap_lock); if (error) goto err_add_memory; -- 1.8.3.1
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