From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752615AbaI3QFa (ORCPT ); Tue, 30 Sep 2014 12:05:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45186 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751786AbaI3QF2 (ORCPT ); Tue, 30 Sep 2014 12:05:28 -0400 Date: Tue, 30 Sep 2014 12:05:10 -0400 From: Dave Jones To: Linus Torvalds Cc: Al Viro , Linux Kernel , Rik van Riel , Ingo Molnar , Michel Lespinasse Subject: Re: pipe/page fault oddness. Message-ID: <20140930160510.GA15903@redhat.com> Mail-Followup-To: Dave Jones , Linus Torvalds , Al Viro , Linux Kernel , Rik van Riel , Ingo Molnar , Michel Lespinasse References: <20140930033327.GA14558@redhat.com> <20140930043309.GA16196@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 30, 2014 at 08:52:08AM -0700, Linus Torvalds wrote: > So if it's looping on that fault, what seems to happen is that the > page fault keeps happening. > > Can you recreate this? Because if you can, please try to revert commit > e4a1cc56e4d7 ("x86: mm: drop TLB flush from ptep_set_access_flags"). > Maybe the TLB has it read-only, and it doesn't get flushed, and the > page fault happens over and over again. I left it spinning overnight in case someone wanted me to probe it further, so I haven't tried reproducing it yet. It took ~12 hours yesterday before it got in that state. I'll restart it, and tell it to only use pipe fd's, which might speed things up a little. If I can reproduce it, I'll then try that revert. > What kind of CPU is the problematic machine? There was some question > about just how architectural the whole "TLB entry causing a page fault > gets invalidated automatically" really is. model name : Intel(R) Core(TM) i5-4670T CPU @ 2.30GHz Dave