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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2AACFC433FE for ; Fri, 22 Apr 2022 00:01:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1442758AbiDVADx (ORCPT ); Thu, 21 Apr 2022 20:03:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58126 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1441834AbiDVADw (ORCPT ); Thu, 21 Apr 2022 20:03:52 -0400 Received: from mail-pl1-x62b.google.com (mail-pl1-x62b.google.com [IPv6:2607:f8b0:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E460144769; Thu, 21 Apr 2022 17:00:59 -0700 (PDT) Received: by mail-pl1-x62b.google.com with SMTP id n8so7203855plh.1; Thu, 21 Apr 2022 17:00:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=zNM0T6G9nbgHrNZ4fTkXwyWCBaHcehFw/2xC4YUFDsI=; b=EuvVsx4ZgPslFCb7gOV55CeCnLpdDVKzvax8LPd7QTAK+3cU87Nftp2h7LeD7u3x2U PO69KJYfLa71urQQP2eN+4+QzGZOFbUrNStJDozSoWX4l5jGuO1fYDQUPM7oTzQ8wB2U 8EIgEV6FSttJlevNQj86csduSGRTjcTwZHEIHMy9jGjOczOnergao1IJkSzCCnshkNPJ Py6NTTy2g3djoSt3B+mT0dIwNsW/H2Eqoy9JrURvzKTT9fe9QNKppdTpHmWnLEPGs5gR mcaxAyyi41329d31VgPJuKePYtKsinZGMVLpeuN/3ZZvqvZv6ZUF8piVfQllRNkVMPdm 7ZLw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition :content-transfer-encoding:in-reply-to; bh=zNM0T6G9nbgHrNZ4fTkXwyWCBaHcehFw/2xC4YUFDsI=; b=4HnZN7U4hdqGNz2gxOt8cs4uMQhPhHWINIIi229/C8bJf0VHPpeotkrASIZQVu5SD+ 29/ZmnGL55SEpj4luZPkl9u/IDXg3EEliIXD65sW6l1eRUMCYKpNH9jTTCPR2ro1FP4/ Sw7Jy+ZTRWsC1dRz8TjxreC9HHaBYT33kq9tXbcPuUNxd1YHMFkGtObGvXRBH7RpvJe2 PAfMxjlNlAlrbnQEhdXBHfMBXGJeWoC/8xxuehwBuAFmdZ+JBmTzKovtq5OeCtwHZJ5F 6dBZ9MxRIff1TYTMxUrgnJxBLgacFLc9R9HdN7P+wuMUTzvwfMYSATnRWTzbn+R3kBFb ONHA== X-Gm-Message-State: AOAM530i/cMQ54mTDXH5D/Fql11fBRUh4n9+wa4q5ZSfoePjpwt5YESz 9wjQigu0C9OugzHUdp7jl3g= X-Google-Smtp-Source: ABdhPJxz3NmXXbUUbQ3NvykiAKXEknpp47eUrgOLe/3aWtrn3sSIrFY8IHtbDQGUfcjACG6SN923fA== X-Received: by 2002:a17:902:ab56:b0:15a:ccc7:a311 with SMTP id ij22-20020a170902ab5600b0015accc7a311mr1722336plb.22.1650585659276; Thu, 21 Apr 2022 17:00:59 -0700 (PDT) Received: from localhost ([2620:10d:c090:400::5:15fa]) by smtp.gmail.com with ESMTPSA id ck20-20020a17090afe1400b001cd4989ff3dsm4180906pjb.4.2022.04.21.17.00.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Apr 2022 17:00:58 -0700 (PDT) Sender: Tejun Heo Date: Thu, 21 Apr 2022 14:00:56 -1000 From: Tejun Heo To: Michal =?iso-8859-1?Q?Koutn=FD?= Cc: Tadeusz Struk , cgroups@vger.kernel.org, Zefan Li , Johannes Weiner , Christian Brauner , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , netdev@vger.kernel.org, bpf@vger.kernel.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+e42ae441c3b10acf9e9d@syzkaller.appspotmail.com Subject: Re: [PATCH] cgroup: don't queue css_release_work if one already pending Message-ID: References: <20220412192459.227740-1-tadeusz.struk@linaro.org> <20220414164409.GA5404@blackbody.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220414164409.GA5404@blackbody.suse.cz> Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Apr 14, 2022 at 06:44:09PM +0200, Michal Koutný wrote: > I suspect the double-queuing is a result of the fact that there exists > only the single reference to the css->refcnt. I.e. it's > percpu_ref_kill_and_confirm()'d and released both at the same time. > > (Normally (when not killing the last reference), css->destroy_work reuse > is not a problem because of the sequenced chain > css_killed_work_fn()->css_put()->css_release().) If this is the case, we need to hold an extra reference to be put by the css_killed_work_fn(), right? Thanks. -- tejun