From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935027Ab3DPAV2 (ORCPT ); Mon, 15 Apr 2013 20:21:28 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:39267 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933533Ab3DPAV0 (ORCPT ); Mon, 15 Apr 2013 20:21:26 -0400 Date: Mon, 15 Apr 2013 17:21:23 -0700 From: Michel Lespinasse To: Hugh Dickins Cc: Vivek Goyal , linux kernel mailing list , Rik van Riel , "Paul E. McKenney" , Andrew Morton Subject: Re: 3.9-rc5: Encountedred INFO: rcu_sched self-detected stall on CPU due to 09a9f1d27 Message-ID: <20130416002123.GA29465@google.com> References: <20130412181348.GA2253@redhat.com> <20130415163552.GA31868@redhat.com> <20130415173424.GB31868@redhat.com> <20130415175929.GB30583@redhat.com> <20130415191304.GC30583@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 On Mon, Apr 15, 2013 at 2:47 PM, Hugh Dickins wrote: > --- 3.9-rc7/mm/mlock.c 2013-04-01 09:08:05.736012852 -0700 > +++ linux/mm/mlock.c 2013-04-15 14:20:24.454773245 -0700 > @@ -397,8 +397,7 @@ int __mm_populate(unsigned long start, u > long ret = 0; > > VM_BUG_ON(start & ~PAGE_MASK); > - VM_BUG_ON(len != PAGE_ALIGN(len)); > - end = start + len; > + end = start + PAGE_ALIGN(len); > > for (nstart = start; nstart < end; nstart = nend) { > /* Yes, there was originally an issue with page alignment in mmap as well, which was fixed by making sure mmap now passes the page aligned length to mm_populate(). sys_brk() passes the length as the difference of two page aligned addresses, so it's fine. But vm_brk() doesn't - it calls do_brk() which page aligns the length, but then vm_brk passes the unaligned length to mm_populate(). What do you think of the following ? len is already a PAGE_SIZE multiple when called from sys_brk()... diff --git a/mm/mmap.c b/mm/mmap.c index 0db0de1c2fbe..6af8b0d1c7db 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2557,10 +2557,6 @@ static unsigned long do_brk(unsigned long addr, unsigned long len) pgoff_t pgoff = addr >> PAGE_SHIFT; int error; - len = PAGE_ALIGN(len); - if (!len) - return addr; - flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags; error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED); @@ -2643,6 +2639,10 @@ unsigned long vm_brk(unsigned long addr, unsigned long len) unsigned long ret; bool populate; + len = PAGE_ALIGN(len); + if (!len) + return addr; + down_write(&mm->mmap_sem); ret = do_brk(addr, len); populate = ((mm->def_flags & VM_LOCKED) != 0); -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies.