From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx150.postini.com [74.125.245.150]) by kanga.kvack.org (Postfix) with SMTP id 0FEE36B0071 for ; Wed, 24 Oct 2012 20:08:14 -0400 (EDT) Received: by mail-pa0-f41.google.com with SMTP id fa10so805589pad.14 for ; Wed, 24 Oct 2012 17:08:13 -0700 (PDT) Date: Wed, 24 Oct 2012 17:08:11 -0700 (PDT) From: David Rientjes Subject: Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in numa_maps In-Reply-To: Message-ID: References: <20121008150949.GA15130@redhat.com> <20121017040515.GA13505@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Sasha Levin , Mel Gorman , Peter Zijlstra , Rik van Riel Cc: Dave Jones , Andrew Morton , Linus Torvalds , KOSAKI Motohiro , bhutchings@solarflare.com, Konstantin Khlebnikov , Naoya Horiguchi , Hugh Dickins , KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Wed, 24 Oct 2012, Sasha Levin wrote: > > This should be fixed by 9e7814404b77 ("hold task->mempolicy while > > numa_maps scans.") in 3.7-rc2, can you reproduce any issues reading > > /proc/pid/numa_maps on that kernel? > > I was actually referring to the warnings Dave Jones saw when fuzzing > with trinity after the > original patch was applied. > > I still see the following when fuzzing: > > [ 338.467156] BUG: sleeping function called from invalid context at > kernel/mutex.c:269 > [ 338.473719] in_atomic(): 1, irqs_disabled(): 0, pid: 6361, name: trinity-main > [ 338.481199] 2 locks held by trinity-main/6361: > [ 338.486629] #0: (&mm->mmap_sem){++++++}, at: [] > __do_page_fault+0x1e4/0x4f0 > [ 338.498783] #1: (&(&mm->page_table_lock)->rlock){+.+...}, at: > [] handle_pte_fault+0x3f7/0x6a0 > [ 338.511409] Pid: 6361, comm: trinity-main Tainted: G W > 3.7.0-rc2-next-20121024-sasha-00001-gd95ef01-dirty #74 > [ 338.530318] Call Trace: > [ 338.534088] [] __might_sleep+0x1c3/0x1e0 > [ 338.539358] [] mutex_lock_nested+0x29/0x50 > [ 338.545253] [] mpol_shared_policy_lookup+0x2e/0x90 > [ 338.545258] [] shmem_get_policy+0x2e/0x30 > [ 338.545264] [] get_vma_policy+0x5a/0xa0 > [ 338.545267] [] mpol_misplaced+0x41/0x1d0 > [ 338.545272] [] handle_pte_fault+0x465/0x6a0 > [ 338.545278] [] ? __rcu_read_unlock+0x44/0xb0 > [ 338.545282] [] handle_mm_fault+0x32a/0x360 > [ 338.545286] [] __do_page_fault+0x480/0x4f0 > [ 338.545293] [] ? del_timer+0x26/0x80 > [ 338.545298] [] ? rcu_cleanup_after_idle+0x23/0x170 > [ 338.545302] [] ? rcu_eqs_exit_common+0x64/0x3a0 > [ 338.545305] [] ? rcu_eqs_enter_common+0x7c6/0x970 > [ 338.545309] [] ? rcu_eqs_exit+0x9c/0xb0 > [ 338.545312] [] do_page_fault+0x26/0x40 > [ 338.545317] [] do_async_page_fault+0x30/0xa0 > [ 338.545321] [] async_page_fault+0x28/0x30 > Ok, this looks the same but it's actually a different issue: mpol_misplaced(), which now only exists in linux-next and not in 3.7-rc2, calls get_vma_policy() which may take the shared policy mutex. This happens while holding page_table_lock from do_huge_pmd_numa_page() but also from do_numa_page() while holding a spinlock on the ptl, which is coming from the sched/numa branch. Is there anyway that we can avoid changing the shared policy mutex back into a spinlock (it was converted in b22d127a39dd ["mempolicy: fix a race in shared_policy_replace()"])? Adding Peter, Rik, and Mel to the cc. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org