From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yh0-f43.google.com (mail-yh0-f43.google.com [209.85.213.43]) by kanga.kvack.org (Postfix) with ESMTP id 878D96B0035 for ; Tue, 11 Mar 2014 16:12:57 -0400 (EDT) Received: by mail-yh0-f43.google.com with SMTP id b6so9203597yha.30 for ; Tue, 11 Mar 2014 13:12:57 -0700 (PDT) Received: from aserp1040.oracle.com (aserp1040.oracle.com. [141.146.126.69]) by mx.google.com with ESMTPS id t49si38141945yhd.9.2014.03.11.13.12.56 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 11 Mar 2014 13:12:57 -0700 (PDT) Message-ID: <531F6E43.40901@oracle.com> Date: Tue, 11 Mar 2014 16:12:51 -0400 From: Sasha Levin MIME-Version: 1.0 Subject: Re: mm: mmap_sem lock assertion failure in __mlock_vma_pages_range References: <531F6689.60307@oracle.com> <1394568453.2786.28.camel@buesod1.americas.hpqcorp.net> In-Reply-To: <1394568453.2786.28.camel@buesod1.americas.hpqcorp.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Davidlohr Bueso Cc: "linux-mm@kvack.org" , Andrew Morton , Michel Lespinasse , Rik van Riel , Vlastimil Babka , LKML On 03/11/2014 04:07 PM, Davidlohr Bueso wrote: > On Tue, 2014-03-11 at 15:39 -0400, Sasha Levin wrote: >> Hi all, >> >> I've ended up deleting the log file by mistake, but this bug does seem to be important >> so I'd rather not wait before the same issue is triggered again. >> >> The call chain is: >> >> mlock (mm/mlock.c:745) >> __mm_populate (mm/mlock.c:700) >> __mlock_vma_pages_range (mm/mlock.c:229) >> VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); > > So __mm_populate() is only called by mlock(2) and this VM_BUG_ON seems > wrong as we call it without the lock held: > > up_write(¤t->mm->mmap_sem); > if (!error) > error = __mm_populate(start, len, 0); > return error; > } > >> >> It seems to be a rather simple trace triggered from userspace. The only recent patch >> in the area (that I've noticed) was "mm/mlock: prepare params outside critical region". >> I've reverted it and trying to testing without it. > > Odd, this patch should definitely *not* cause this. In any case every > operation removed from the critical region is local to the function: > > lock_limit = rlimit(RLIMIT_MEMLOCK); > lock_limit >>= PAGE_SHIFT; > locked = len >> PAGE_SHIFT; > > down_write(¤t->mm->mmap_sem); Yeah, this patch doesn't look like it's causing it, I guess it was more of a "you touched this code last - do you still remember what's going on here?" :). It's semi-odd because it seems like an obvious issue to hit with trinity but it's the first time I've seen it and it's probably been there for a while (that BUG_ON is there from 2009). Thanks, Sasha -- 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