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Date: Tue, 28 Jul 2009 09:54:53 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: David Rientjes <rientjes@...gle.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Lee Schermerhorn <lee.schermerhorn@...com>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, miaox@...fujitsu.com, Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Christoph Lameter <cl@...ux-foundation.org>, Paul Menage <menage@...gle.com>, Nick Piggin <nickpiggin@...oo.com.au>, y-goto@...fujitsu.com, Pekka Enberg <penberg@...helsinki.fi>, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [BUG] set_mempolicy(MPOL_INTERLEAV) cause kernel panic On Mon, 27 Jul 2009 17:38:30 -0700 (PDT) David Rientjes <rientjes@...gle.com> wrote: > On Tue, 28 Jul 2009, KAMEZAWA Hiroyuki wrote: > > > Because we dont' update, task->mems_allowed need to be initilaized as > > N_POSSIBLE_NODES. At usual thinking, it should be N_HIGH_MEMORY or > > N_ONLINE_NODES, as my patch does. > > > > On MEM_OFFLINE, cpusets calls scan_for_empty_cpusets() which will > intersect each system cpuset's mems_allowed with N_HIGH_MEMORY. It then > calls update_tasks_nodemask() which will update task->mems_allowed for > each task assigned to those cpusets. This has a callback into the > mempolicy code to rebind the policy with the new mems. > > So there's no apparent issue with memory hotplug in dealing with cpuset > mems, although I suggested that this be done for MEM_GOING_OFFLINE instead > of waiting until the mem is actually offline. > I _wrote_ this is just a side story to bug. online/offline isn't related to this bug. > The problem originally reported here doesn't appear to have anything to do > with hotplug, it looks like it is the result of Lee's observation that > ia64 defaults top_cpuset's mems to N_POSSIBLE, which _should_ have been > updated by cpuset_init_smp(). cpuset_init_smp() just updates cpuset's mask. init's task->mems_allowed is intizialized independently from cpuset's mask. Could you teach me a pointer for Lee's observation ? > So it makes me believe that N_HIGH_MEMORY > isn't actually ready by the time do_basic_setup() is called to be useful. > N_HIGH_MEMORY should be ready when zonelist is built. If not, it's bug. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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