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=-2.0 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 9A576C33C99 for ; Tue, 7 Jan 2020 09:29:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 670F7206DB for ; Tue, 7 Jan 2020 09:29:43 +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="btXi/8aB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727761AbgAGJ3m (ORCPT ); Tue, 7 Jan 2020 04:29:42 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:41508 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727154AbgAGJ3l (ORCPT ); Tue, 7 Jan 2020 04:29:41 -0500 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=sZXc/SFe/LDxQMr1tMtTHpfYzLnb842y8KpXben4b1s=; b=btXi/8aBR87eesFRk9rVTf7MA Lo11ZldNjZKAaB6/9zJZ1gf9NCJZvkST1Vwo004YnQHoByFcCJfif+5Fqu4TzIXw5U0tGlHGJWd+a uAbdPGF/hE+gJrM45w6VbyVJMLfvZdman1WMvJ7duagTokTpaTco+9foSyaY6KC4KEi1apyy3gt3Z MyFzxQQ4CQ3HjQ7Ly+3LO79dRGmdWpV/ITVmEE62USnSeM4Sul7t2Qc2rcdQVThRujD+TAPDdf8sE Ls2wHFbHxc87Oh04zt8FDYANAYG0ibCN0a0J7L1coZDrTWqb/7TS0AcaWpbj9k4F209mloCRCp9DM w5WzTTcmg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iolBA-0000AU-Tt; Tue, 07 Jan 2020 09:29:37 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id A39A4304A59; Tue, 7 Jan 2020 10:28:02 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 24B232B5FBC95; Tue, 7 Jan 2020 10:29:35 +0100 (CET) Date: Tue, 7 Jan 2020 10:29:35 +0100 From: Peter Zijlstra To: Luc Van Oostenryck Cc: Kees Cook , Eric Biggers , linux-kernel@vger.kernel.org, Ingo Molnar , Will Deacon , Elena Reshetova , Thomas Gleixner , Anna-Maria Gleixner , Sebastian Andrzej Siewior , linux-sparse@vger.kernel.org Subject: Re: [PATCH] locking/refcount: add sparse annotations to dec-and-lock functions Message-ID: <20200107092935.GU2844@hirez.programming.kicks-ass.net> References: <20191226152922.2034-1-ebiggers@kernel.org> <20191228114918.GU2827@hirez.programming.kicks-ass.net> <201912301042.FB806E1133@keescook> <20191230191547.GA1501@zzz.localdomain> <201912301131.2C7C51E8C6@keescook> <20191230233814.2fgmsgtnhruhklnu@ltop.local> <20200106154119.GV2810@hirez.programming.kicks-ass.net> <20200106175459.tjuhmdrsusax3s4z@ltop.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200106175459.tjuhmdrsusax3s4z@ltop.local> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 06, 2020 at 06:54:59PM +0100, Luc Van Oostenryck wrote: > On Mon, Jan 06, 2020 at 04:41:19PM +0100, Peter Zijlstra wrote: > > extern bool spin_trylock(spinlock_t *lock) __attribute__((context(lock, 0, spin_trylock(lock)); > > Well, allowing arbitrary conditions would be hard/impossible but you're > only asking to have the *return value* as condition, right? That looks > as reasonably feasible. Just the return value would cover all the known cases yes. At the time I might have been somewhat over ambitious.. > > Basically have sparse do a transform on its own expression tree and > > inject the very same crud we now do manually. This avoids cluttering the > > kernel tree with this nonsense. > > So, a call of a function declared with __acquires() or releases() is > interpreted by Sparse as if the call is immediately followed by an > increase or a decrease of the context. It wouldn't be very hard to > add a new attribute (something like __cond_context) and let Sparse do > as if a call to a function with such attribute is directly followed > by a test of its return value and a corresponding change in the context. > It would boil down to: > > extern bool spin_trylock(lock) __cond_context(lock); > > if (spin_trylock(lock)) { > /* do crap */ > spin_unlock(); > } > > behaving like the following code currently would: > > extern bool spin_trylock(lock); > > if (spin_trylock(lock)) { > __acquire(lock); > /* do crap */ > spin_unlock(); > } > > > Would something like this be satisfactory? Very much so, Thanks!