Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2060EC433EF for ; Thu, 18 Nov 2021 08:45:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBC82619BB for ; Thu, 18 Nov 2021 08:45:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244766AbhKRIso (ORCPT ); Thu, 18 Nov 2021 03:48:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243165AbhKRIsL (ORCPT ); Thu, 18 Nov 2021 03:48:11 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D40B1C061210 for ; Thu, 18 Nov 2021 00:44:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=96S4EthB+6zIOtMMZ50m2yFtwma9si/mTFRJme+WPvU=; b=oaxBH2FfzEJgcO3Q5kmi4rhOiQ Fie+uS6wSt0O5tQpfW/lv6Aqiw/WN+zV4KsAMPAW6G+LSEGCaWO2Pn0riDgP6NLLCpyRFktArsWwS Erd9iRCxbH/7q3ULr8q+AFGMIGdH4ei0LiHtJNHb7msU166ccsP6yV2dPi+h++ta29FCrpI/Gevca ZRK5pPfrQIFdVcWQX7trKgnGv4dJPZ26wA2/52dD16VlnR21akne5tBydfKHEBaG3ENWUpw3axos0 ZAXpU9smE4rVPE+qs9AknWIUVnctPJ5V+f0Rvp6NACgH8B2wPjJ/XGybCguMmZZGiL5CbojzdYUGA gqeeZ75A==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mnd24-008JLA-Pr; Thu, 18 Nov 2021 08:44:37 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 94D4E30001B; Thu, 18 Nov 2021 09:44:36 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 833B72C99C22B; Thu, 18 Nov 2021 09:44:36 +0100 (CET) Date: Thu, 18 Nov 2021 09:44:36 +0100 From: Peter Zijlstra To: yajun.deng@linux.dev Cc: will@kernel.org, boqun.feng@gmail.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] refcount: introduce refcount_is_one() helper function Message-ID: References: <20211118074200.GF174703@worktop.programming.kicks-ass.net> <20211118035328.5730-1-yajun.deng@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 18, 2021 at 08:12:56AM +0000, yajun.deng@linux.dev wrote: > November 18, 2021 3:42 PM, "Peter Zijlstra" wrote: > > > On Thu, Nov 18, 2021 at 11:53:28AM +0800, Yajun Deng wrote: > > > >> There are many cases where it is necessary to determine if refcount is one, > >> introduce refcount_is_one() helper function for these cases. > > > > Give me one that is not racy? > > The following determine refcount is one, 35 count. Very good, now get me one that isn't broken :-)