From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932887AbeEHXDA (ORCPT ); Tue, 8 May 2018 19:03:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33064 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755529AbeEHXC7 (ORCPT ); Tue, 8 May 2018 19:02:59 -0400 Date: Tue, 8 May 2018 16:02:57 -0700 From: Andrew Morton To: Vlastimil Babka Cc: Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, linux-mm@kvack.org, tglx@linutronix.de, "Steven J . Hill" , Tejun Heo , Christoph Lameter Subject: Re: [PATCH REPOST] Revert mm/vmstat.c: fix vmstat_update() preemption BUG Message-Id: <20180508160257.6e19707ccf1dabe5ec9e8847@linux-foundation.org> In-Reply-To: <513014a0-a149-5141-a5a0-9b0a4ce9a8d8@suse.cz> References: <20180504104451.20278-1-bigeasy@linutronix.de> <513014a0-a149-5141-a5a0-9b0a4ce9a8d8@suse.cz> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 7 May 2018 09:31:05 +0200 Vlastimil Babka wrote: > In any case I agree that the revert should be done immediately even > before fixing the underlying bug. The preempt_disable/enable doesn't > prevent the bug, it only prevents the debugging code from actually > reporting it! Note that it's debugging code (CONFIG_DEBUG_PREEMPT) that > production kernels most likely don't have enabled, so we are not even > helping them not crash (while allowing possible data corruption). Grumble. I don't see much benefit in emitting warnings into end-users' logs for bugs which we already know about. The only thing this buys us is that people will hassle us if we forget to fix the bug, and how pathetic is that? I mean, we may as well put printk("don't forget to fix the vmstat_update() bug!\n"); into start_kernel().