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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41B41C0218A for ; Thu, 30 Jan 2025 22:38:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7C87328029C; Thu, 30 Jan 2025 17:37:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 778C0280299; Thu, 30 Jan 2025 17:37:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6406428029C; Thu, 30 Jan 2025 17:37:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 44CAE280299 for ; Thu, 30 Jan 2025 17:37:59 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id E6BF4A034A for ; Thu, 30 Jan 2025 22:37:58 +0000 (UTC) X-FDA: 83065582236.16.E847E54 Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf03.hostedemail.com (Postfix) with ESMTP id 1887620003 for ; Thu, 30 Jan 2025 22:37:56 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=qhz+CEhX; spf=pass (imf03.hostedemail.com: domain of akpm@linux-foundation.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1738276677; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=TakTU9J6bfpHeCHmLM7S07ALrTqSfJs8/8LueaVmsAs=; b=vZtoKtc2q9HCK0dSJNyEmSWJrHMSfczvOoY1A+NCGcSiOMW8Os5ct8ICKTkKlIBSOjmTzQ SaVq4WUexE6E4s6fKjjVZkXLNbaJH1zjm9IJUPRumZJk1tOocOf/5ikm28I2FyLYqQxiaW 8G4xWEyEmNfVI4+Y3jwp1reKNSPRrNk= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=qhz+CEhX; spf=pass (imf03.hostedemail.com: domain of akpm@linux-foundation.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1738276677; a=rsa-sha256; cv=none; b=W6As6zhr7N+RbgvcQdLecx2kmBI0nGoj5kC8poaZs5U1X+TREi/QY0IrgXEAHafGKBH9vp EbZfJ6qg59e8ORRJ8MNNG8uEg7omA9n/PL/6IagpnJ0P2gjPmArkIaHTPGkot50LVs8INe b2zvvxFyJJ+u31PY/n2QDimaGZmHQhs= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 864A4A42138; Thu, 30 Jan 2025 22:36:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4D887C4CED2; Thu, 30 Jan 2025 22:37:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1738276675; bh=RsT+cN+IqZrca/sfcUXS4hAuAouyjftXrA3xfHri/m8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qhz+CEhXICkn0jM8lJT8fdw57VIsg72Lz0XhZHpDVAWpeM2PKCSs1x7elh59mqcJU vXJwfAUj/PYIeBgmH7lalHq3R2muaTnviixMFnft70NgqqKKJbxOr6d/DbMoV3Oi22 kOFWUI8NEtokisuK+fCLAVpZ4LpfVx/d8Zp4kbnQ= Date: Thu, 30 Jan 2025 14:37:54 -0800 From: Andrew Morton To: Lorenzo Stoakes Cc: Christian Brauner , Shuah Khan , "Liam R . Howlett" , Suren Baghdasaryan , Vlastimil Babka , pedro.falcato@gmail.com, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Oliver Sang , John Hubbard , Tejun Heo , Johannes Weiner , Michal Koutny , Shakeel Butt Subject: Re: [PATCH v7 0/6] introduce PIDFD_SELF* sentinels Message-Id: <20250130143754.1b8bb87bfb15175dd434529b@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 1887620003 X-Stat-Signature: i6ykm6gcgczeomyp8k66gd48q5mqw5qf X-Rspam-User: X-HE-Tag: 1738276676-867292 X-HE-Meta: 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 E14/F1Fv s0WZSADcIV4WJ2+g5O8SX8+Uh7Dp862tcHk/NNi17tUMQmyVgx2POer/lDySJV1iRRiQdMsmar/acpsTqDFnAdGDsw3WIagdT/E8rDvr5t0yD/XNAaLDbqn76GIEBuyxvwTan7h33op6zwFzr8I/8vIv5ImAugTF3GrpVdkwV2d7/TdZfki+ApoXggxgUIRXGrjUlcmk8eBQK7pC/24Jf5ZtIVRhPc3dTc3Cg1uhh5ZhRuRQuMD1bOcfy/Gr5T6/dSCDw1+bCd+nSiG/kF6Lx1HwpVE/bzp64JyU67e8NKPz/NC+SYNzdlZSK4i5eTou97Dk+pQMu1ZNtRwgQXW5R2H0UOSB8Odtni5B1D9FiJmx3a+jRhSOUz6G99L4iE5xP3D3yI/S8c2/PoE4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000229, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 30 Jan 2025 20:40:25 +0000 Lorenzo Stoakes wrote: > If you wish to utilise a pidfd interface to refer to the current process or > thread it is rather cumbersome, requiring something like: > > int pidfd = pidfd_open(getpid(), 0 or PIDFD_THREAD); > > ... > > close(pidfd); > > Or the equivalent call opening /proc/self. It is more convenient to use a > sentinel value to indicate to an interface that accepts a pidfd that we > simply wish to refer to the current process thread. > The above code sequence doesn't seem at all onerous. I'm not understanding why it's worth altering the kernel to permit this little shortcut?