From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756393Ab3LSMEB (ORCPT ); Thu, 19 Dec 2013 07:04:01 -0500 Received: from cantor2.suse.de ([195.135.220.15]:50497 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753448Ab3LSMAK (ORCPT ); Thu, 19 Dec 2013 07:00:10 -0500 Date: Thu, 19 Dec 2013 12:00:07 +0000 From: Mel Gorman To: Andrew Morton Cc: Alex Thorlton , Rik van Riel , Sasha Levin , Linux-MM , LKML Subject: [PATCH] mm: Remove bogus warning in copy_huge_pmd Message-ID: <20131219120007.GJ11295@suse.de> References: <1386690695-27380-1-git-send-email-mgorman@suse.de> <1386690695-27380-11-git-send-email-mgorman@suse.de> <52B0D5F9.5030208@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <52B0D5F9.5030208@oracle.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sasha Levin reported the following warning being triggered [ 1704.594807] WARNING: CPU: 28 PID: 35287 at mm/huge_memory.c:887 copy_huge_pmd+0x145/ 0x3a0() [ 1704.597258] Modules linked in: [ 1704.597844] CPU: 28 PID: 35287 Comm: trinity-main Tainted: G W 3.13.0-rc4-next-20131217-sasha-00013-ga878504-dirty #4149 [ 1704.599924] 0000000000000377e delta! pid slot 27 [36258]: old:2 now:537927697 diff: 537927695 ffff8803593ddb90 ffffffff8439501c ffffffff854722c1 [ 1704.604846] 0000000000000000 ffff8803593ddbd0 ffffffff8112f8ac ffff8803593ddbe0 [ 1704.606391] ffff88034bc137f0 ffff880e41677000 8000000b47c009e4 ffff88034a638000 [ 1704.608008] Call Trace: [ 1704.608511] [] dump_stack+0x52/0x7f [ 1704.609699] [] warn_slowpath_common+0x8c/0xc0 [ 1704.612617] [] warn_slowpath_null+0x1a/0x20 [ 1704.614043] [] copy_huge_pmd+0x145/0x3a0 [ 1704.615587] [] copy_page_range+0x3f2/0x560 [ 1704.616869] [] ? rwsem_wake+0x51/0x70 [ 1704.617942] [] dup_mmap+0x2c9/0x3d0 [ 1704.619146] [] dup_mm+0xad/0x150 [ 1704.620051] [] copy_process+0xa68/0x12e0 [ 1704.622976] [] ? __lock_release+0x1da/0x1f0 [ 1704.624234] [] do_fork+0x96/0x270 [ 1704.624975] [] ? context_tracking_user_exit+0x195/0x1d0 [ 1704.626427] [] ? trace_hardirqs_on+0xd/0x10 [ 1704.627681] [] SyS_clone+0x16/0x20 [ 1704.628833] [] stub_clone+0x69/0x90 [ 1704.629672] [] ? tracesys+0xdd/0xe2 This warning was introduced by "mm: numa: Avoid unnecessary disruption of NUMA hinting during migration" for paranoia reasons but the warning is bogus. I was thinking of parallel races between NUMA hinting faults and forks but this warning would also be triggered by a parallel reclaim splitting a THP during a fork. Remote the bogus warning. Signed-off-by: Mel Gorman --- mm/huge_memory.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index e3b6a75..468bd3a 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -883,9 +883,6 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, goto out_unlock; } - /* mmap_sem prevents this happening but warn if that changes */ - WARN_ON(pmd_trans_migrating(pmd)); - if (unlikely(pmd_trans_splitting(pmd))) { /* split huge page running from under us */ spin_unlock(src_ptl);