From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f50.google.com (mail-pa0-f50.google.com [209.85.220.50]) by kanga.kvack.org (Postfix) with ESMTP id A585C6B0035 for ; Mon, 28 Apr 2014 18:07:01 -0400 (EDT) Received: by mail-pa0-f50.google.com with SMTP id rd3so6284818pab.23 for ; Mon, 28 Apr 2014 15:07:01 -0700 (PDT) Received: from mail-pd0-x22d.google.com (mail-pd0-x22d.google.com [2607:f8b0:400e:c02::22d]) by mx.google.com with ESMTPS id qf5si11312608pac.170.2014.04.28.15.06.59 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 28 Apr 2014 15:06:59 -0700 (PDT) Received: by mail-pd0-f173.google.com with SMTP id p10so5879956pdj.18 for ; Mon, 28 Apr 2014 15:06:59 -0700 (PDT) Date: Mon, 28 Apr 2014 15:05:43 -0700 (PDT) From: Hugh Dickins Subject: Re: [BUG] kernel BUG at mm/vmacache.c:85! In-Reply-To: Message-ID: References: <535EA976.1080402@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: "Srivatsa S. Bhat" , Linux MM , "linux-kernel@vger.kernel.org" , Davidlohr Bueso , Rik van Riel , Michel Lespinasse , "akpm@linux-foundation.org" On Mon, 28 Apr 2014, Linus Torvalds wrote: > On Mon, Apr 28, 2014 at 2:20 PM, Linus Torvalds > wrote: > > > > That said, the bug does seem to be that some path doesn't invalidate > > the vmacache sufficiently, or something inserts a vmacache entry into > > the current process when looking up a remote process or whatever. > > Davidlohr, ideas? > > Maybe we missed some use_mm() call. That will change the current mm > without flushing the vma cache. The code considers kernel threads to > be bad targets for vma caching for this reason (and perhaps others), > but maybe we missed something. > > I wonder if we should just invalidate the vma cache in use_mm(), and > remote the "kernel tasks are special" check. > > Srivatsa, are you doing something peculiar on that system that would > trigger this? I see some kdump failures in the log, anything else? I doubt that the vmacache has anything to do with the real problem (though it *might* suggest that vmacache is less robust than what it replaced - maybe). The log is so full of userspace SIGSEGVs and General Protection faults, it looks like userspace was utterly broken by some kernel bug messing up the address space. Hugh -- 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