From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751208AbdJDVmo (ORCPT ); Wed, 4 Oct 2017 17:42:44 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:30378 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751120AbdJDVmn (ORCPT ); Wed, 4 Oct 2017 17:42:43 -0400 To: hannes@cmpxchg.org Cc: akpm@linux-foundation.org, alan@llwyncelyn.cymru, hch@lst.de, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 1/2] Revert "vmalloc: back off when the current task is killed" From: Tetsuo Handa References: <20171003225504.GA966@cmpxchg.org> <20171004185813.GA2136@cmpxchg.org> <20171004185906.GB2136@cmpxchg.org> <20171004210027.GA2973@cmpxchg.org> In-Reply-To: <20171004210027.GA2973@cmpxchg.org> Message-Id: <201710050642.JJI34818.QFSHJOMOtFOLFV@I-love.SAKURA.ne.jp> X-Mailer: Winbiff [Version 2.51 PL2] X-Accept-Language: ja,en,zh Date: Thu, 5 Oct 2017 06:42:38 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Johannes Weiner wrote: > On Thu, Oct 05, 2017 at 05:49:43AM +0900, Tetsuo Handa wrote: > > On 2017/10/05 3:59, Johannes Weiner wrote: > > > But the justification to make that vmalloc() call fail like this isn't > > > convincing, either. The patch mentions an OOM victim exhausting the > > > memory reserves and thus deadlocking the machine. But the OOM killer > > > is only one, improbable source of fatal signals. It doesn't make sense > > > to fail allocations preemptively with plenty of memory in most cases. > > > > By the time the current thread reaches do_exit(), fatal_signal_pending(current) > > should become false. As far as I can guess, the source of fatal signal will be > > tty_signal_session_leader(tty, exit_session) which is called just before > > tty_ldisc_hangup(tty, cons_filp != NULL) rather than the OOM killer. I don't > > know whether it is possible to make fatal_signal_pending(current) true inside > > do_exit() though... > > It's definitely not the OOM killer, the memory situation looks fine > when this happens. I didn't look closer where the signal comes from. > Then, we could check tsk_is_oom_victim() instead of fatal_signal_pending(). > That said, we trigger this issue fairly easily. We tested the revert > over night on a couple thousand machines, and it fixed the issue > (whereas the control group still saw the crashes). >