Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756769AbaD1WOy (ORCPT ); Mon, 28 Apr 2014 18:14:54 -0400 Received: from g4t3426.houston.hp.com ([15.201.208.54]:54613 "EHLO g4t3426.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752211AbaD1WOw (ORCPT ); Mon, 28 Apr 2014 18:14:52 -0400 Message-ID: <1398723290.25549.20.camel@buesod1.americas.hpqcorp.net> Subject: Re: [BUG] kernel BUG at mm/vmacache.c:85! From: Davidlohr Bueso To: Hugh Dickins Cc: Linus Torvalds , "Srivatsa S. Bhat" , Linux MM , "linux-kernel@vger.kernel.org" , Rik van Riel , Michel Lespinasse , "akpm@linux-foundation.org" Date: Mon, 28 Apr 2014 15:14:50 -0700 In-Reply-To: References: <535EA976.1080402@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.6.4 (3.6.4-3.fc18) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2014-04-28 at 15:05 -0700, Hugh Dickins wrote: > 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. I think that returning some stale/bogus vma is causing those segfaults in udev. It shouldn't occur in a normal scenario. What puzzles me is that it's not always reproducible. This makes me wonder what else is going on... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/