From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f175.google.com (mail-pd0-f175.google.com [209.85.192.175]) by kanga.kvack.org (Postfix) with ESMTP id 9FB2C6B0035 for ; Tue, 11 Mar 2014 16:30:54 -0400 (EDT) Received: by mail-pd0-f175.google.com with SMTP id x10so58806pdj.6 for ; Tue, 11 Mar 2014 13:30:54 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTP id tu7si106233pac.193.2014.03.11.13.30.52 for ; Tue, 11 Mar 2014 13:30:53 -0700 (PDT) Date: Tue, 11 Mar 2014 13:30:51 -0700 From: Andrew Morton Subject: Re: mm: mmap_sem lock assertion failure in __mlock_vma_pages_range Message-Id: <20140311133051.bf5ca716ef189746ebcff431@linux-foundation.org> In-Reply-To: <1394568453.2786.28.camel@buesod1.americas.hpqcorp.net> References: <531F6689.60307@oracle.com> <1394568453.2786.28.camel@buesod1.americas.hpqcorp.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Davidlohr Bueso Cc: Sasha Levin , "linux-mm@kvack.org" , Michel Lespinasse , Rik van Riel , Vlastimil Babka , LKML On Tue, 11 Mar 2014 13:07:33 -0700 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; > } __mm_populate() pretty clearly calls __mlock_vma_pages_range() under down_read(mm->mmap_sem). I worry about what happens if __get_user_pages decides to do if (ret & VM_FAULT_RETRY) { if (nonblocking) *nonblocking = 0; return i; } uh-oh, that just cleared __mm_populate()'s `locked' variable and we'll forget to undo mmap_sem. That won't explain this result, but it's a potential problem. All I can think is that find_vma() went and returned a vma from a different mm, which would be odd. How about I toss this in there? --- a/mm/vmacache.c~a +++ a/mm/vmacache.c @@ -72,8 +72,10 @@ struct vm_area_struct *vmacache_find(str for (i = 0; i < VMACACHE_SIZE; i++) { struct vm_area_struct *vma = current->vmacache[i]; - if (vma && vma->vm_start <= addr && vma->vm_end > addr) + if (vma && vma->vm_start <= addr && vma->vm_end > addr) { + BUG_ON(vma->vm_mm != mm); return vma; + } } return NULL; _ -- 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