From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EDF62C0650F for ; Thu, 8 Aug 2019 07:03:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC19220665 for ; Thu, 8 Aug 2019 07:03:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731089AbfHHHDb (ORCPT ); Thu, 8 Aug 2019 03:03:31 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:52377 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725817AbfHHHDb (ORCPT ); Thu, 8 Aug 2019 03:03:31 -0400 Received: from p200300ddd71876597e7a91fffec98e25.dip0.t-ipconnect.de ([2003:dd:d718:7659:7e7a:91ff:fec9:8e25]) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1hvcRp-0001ck-0m; Thu, 08 Aug 2019 09:02:53 +0200 Date: Thu, 8 Aug 2019 09:02:47 +0200 (CEST) From: Thomas Gleixner To: Christoph Hellwig cc: LKML , Peter Zijlstra , Ingo Molnar , Sebastian Siewior , Anna-Maria Gleixner , Steven Rostedt , Julia Cartwright , Jan Kara , Theodore Tso , Matthew Wilcox , Alexander Viro , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Jan Kara , Mark Fasheh , Joseph Qi , Joel Becker Subject: Re: [patch V2 0/7] fs: Substitute bit-spinlocks for PREEMPT_RT and debugging In-Reply-To: <20190806061119.GA17492@infradead.org> Message-ID: References: <20190801010126.245731659@linutronix.de> <20190802075612.GA20962@infradead.org> <20190806061119.GA17492@infradead.org> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 5 Aug 2019, Christoph Hellwig wrote: > On Fri, Aug 02, 2019 at 11:07:53AM +0200, Thomas Gleixner wrote: > > Last time I did, there was resistance :) > > Do you have a pointer? Note that in the buffer head case maybe > a hash lock based on the page address is even better, as we only > ever use the lock in the first buffer head of a page anyway.. I need to search my archives, but I'm on a spotty and slow connection right now. Will do so when back home. > > What about the page lock? > > > > mm/slub.c: bit_spin_lock(PG_locked, &page->flags); > > One caller ouf of a gazillion that spins on the page lock instead of > sleepign on it like everyone else. That should not have passed your > smell test to start with :) I surely stared at it, but that cannot sleep. It's in the middle of a preempt and interrupt disabled region and used on architectures which do not support CMPXCHG_DOUBLE and ALIGNED_STRUCT_PAGE ... Thanks, tglx