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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 541A6C433FF for ; Thu, 8 Aug 2019 07:28:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1D3E42187F for ; Thu, 8 Aug 2019 07:28:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="un30FUNr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731178AbfHHH2O (ORCPT ); Thu, 8 Aug 2019 03:28:14 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:55956 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730887AbfHHH2O (ORCPT ); Thu, 8 Aug 2019 03:28:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=DKEna/7+DBlpAfStQG61tcPutdE/j8S3q0Xub5Jf2r4=; b=un30FUNrFKnGvbWxL+njNsq6w ++c+PapB3gmasvpSSJNS+t7qIC6VEKohHyFrdnrsPOdHe5wMvSmcn2TtO9b7amLOy/9tSxwIjRfef E0JMnsizL9DjhElzg5QPiYm5PFzKiyYmRKkcblFvHgQN6mxrZgeWHQpX9tJYL4Grkefnfez8PXmmj oR0MEo8Gj5RIYdKyL1/ygwECjZibsh8aAeEMKW48rh4xVD4QQ1oW4miqa4CvdVMdVGhN9k5y/dTa/ uIJJeOoPNxrK92pSWJrFJslttBNoz83TgGFs9cKRTlFA6g1tknT6SmjO9aYXzSLmSJzrV8ppXkVfn 5YtT/5Unw==; Received: from hch by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hvcqF-00080i-Ug; Thu, 08 Aug 2019 07:28:07 +0000 Date: Thu, 8 Aug 2019 00:28:07 -0700 From: Christoph Hellwig To: Thomas Gleixner Cc: Christoph Hellwig , 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 Message-ID: <20190808072807.GA25259@infradead.org> References: <20190801010126.245731659@linutronix.de> <20190802075612.GA20962@infradead.org> <20190806061119.GA17492@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.4 (2019-03-13) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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. Does SLUB work on -rt at all?