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 D7AD5C0650F for ; Thu, 8 Aug 2019 07:54:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B39A8217D7 for ; Thu, 8 Aug 2019 07:54:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731716AbfHHHyd (ORCPT ); Thu, 8 Aug 2019 03:54:33 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:52472 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725796AbfHHHyd (ORCPT ); Thu, 8 Aug 2019 03:54:33 -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 1hvdFR-0002M4-Ph; Thu, 08 Aug 2019 09:54:09 +0200 Date: Thu, 8 Aug 2019 09:54:03 +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: <20190808072807.GA25259@infradead.org> Message-ID: References: <20190801010126.245731659@linutronix.de> <20190802075612.GA20962@infradead.org> <20190806061119.GA17492@infradead.org> <20190808072807.GA25259@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 Thu, 8 Aug 2019, Christoph Hellwig wrote: > On Thu, Aug 08, 2019 at 09:02:47AM +0200, Thomas Gleixner wrote: > > > > 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 ... > > I know. But the problem here is that normally PG_locked is used together > with wait_on_page_bit_*, but this one instances uses the bit spinlock > helpers. This is the equivalent of calling spin_lock on a struct mutex > rather than having a mutex_lock_spin helper for this case. Yes, I know :( > Does SLUB work on -rt at all? It's the only allocator we support with a few tweaks :) Thanks, tglx