On Sun, 12 Feb 2017 17:35:00 -0800 Dan Williams wrote: > On Sun, Feb 12, 2017 at 5:25 PM, Masayoshi Mizuma > <m.mizuma@xxxxxxxxxxxxxx> 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(). I understand. Thanks. --- Masayoshi Mizuma