From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932386AbbLNMG0 (ORCPT ); Mon, 14 Dec 2015 07:06:26 -0500 Received: from mail-wm0-f41.google.com ([74.125.82.41]:38534 "EHLO mail-wm0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932268AbbLNMGZ (ORCPT ); Mon, 14 Dec 2015 07:06:25 -0500 Date: Mon, 14 Dec 2015 13:06:22 +0100 From: Michal Hocko To: Linus Torvalds Cc: Andrew Morton , Johannes Weiner , Hugh Dickins , Daniel Vetter , David Airlie , Mika Westerber , Andrey Ryabinin , linux-mm@kvack.org, LKML Subject: Re: !PageLocked from shmem charge path hits VM_BUG_ON with 4.4-rc4 Message-ID: <20151214120621.GA4339@dhcp22.suse.cz> References: <20151214100156.GA4540@dhcp22.suse.cz> <20151214110320.GB9544@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151214110320.GB9544@dhcp22.suse.cz> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 14-12-15 12:03:20, Michal Hocko wrote: > JFYI: Andrey Ryabinin has noticed that this might be related to > http://lkml.kernel.org/r/CAPAsAGzrOQAABhOta_o-MzocnikjPtwJLfEKQJ3n5mbBm0T7Bw@mail.gmail.com > > and indeed if somebody with pending signals would do wait_on_page_locked > then it could race AFAIU. No, a simple lock_page would fail to lock the page (thanks Andrey for the clarification in the parallel email thread). I have missed that __lock_page uses bit_wait_io and that would return EINTR when using signal_pending. The fix has changed that to singnal_pending_state so this will not happen anymore. I think the mystery is solved... -- Michal Hocko SUSE Labs