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=-2.2 required=3.0 tests=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 B4DD6C4321A for ; Fri, 28 Jun 2019 14:31:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 916442064B for ; Fri, 28 Jun 2019 14:31:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726780AbfF1ObP (ORCPT ); Fri, 28 Jun 2019 10:31:15 -0400 Received: from mail-wr1-f68.google.com ([209.85.221.68]:44312 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726657AbfF1ObO (ORCPT ); Fri, 28 Jun 2019 10:31:14 -0400 Received: by mail-wr1-f68.google.com with SMTP id r16so4670282wrl.11 for ; Fri, 28 Jun 2019 07:31:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=vIGColdwlEbXzgqC2nSGDJI+imgI3Vqv6hRTUWcURzQ=; b=IKO1lxe6F6+Eh0XtTiaxcQsNy4mX420Hr2POpi8SbBYYT2jUwSKtRR/nGTcJI1dtqP yIyyKy/aVEnDw39O1ZwM/gC79cROYEjZEv5y0xrEL0FZlpIlg3HOrnJzrTRjoQmxzBWM pqO/xK/41rPjIZPpnRvuUcBBTadxfyhKIP2Fs8B9CwBwUx6zobx4CbXjgDXrXXGcOhfH suz8ZMmoRgRYLDnkvMacShy3pu2QtrRFaWlxExjEmcMfucatoSx3E42AVqN9dul5CL5e NWWKXdlap0INbsOcex3vcPKuVAeHiSyswII8dDNe6ZTQKWN1TBfKdJdTbTAj0AaVAAGf k2DQ== X-Gm-Message-State: APjAAAUnQ+YhvCl5E4nfKzRB0Uy2vT5IwDn3KJFwEO5bFgl/kHOERC3x ckwCjOSDkUXz7Dl45iC6i1SbEYAiQmA= X-Google-Smtp-Source: APXvYqwx09hYWkLmHko84vnw++BV/pG5dTLGCo1wtOyMVyrIMDG9Y8/TsrSYd/185KxfT1jmBBtkAg== X-Received: by 2002:adf:ea8b:: with SMTP id s11mr1636482wrm.100.1561732272911; Fri, 28 Jun 2019 07:31:12 -0700 (PDT) Received: from localhost.localdomain ([151.29.165.245]) by smtp.gmail.com with ESMTPSA id j7sm3290365wru.54.2019.06.28.07.31.11 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 28 Jun 2019 07:31:11 -0700 (PDT) Date: Fri, 28 Jun 2019 16:31:09 +0200 From: Juri Lelli To: Peter Zijlstra Cc: mingo@redhat.com, rostedt@goodmis.org, tj@kernel.org, linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it, claudio@evidence.eu.com, tommaso.cucinotta@santannapisa.it, bristot@redhat.com, mathieu.poirier@linaro.org, lizefan@huawei.com, cgroups@vger.kernel.org Subject: Re: [PATCH v8 5/8] cgroup/cpuset: convert cpuset_mutex to percpu_rwsem Message-ID: <20190628143109.GX26005@localhost.localdomain> References: <20190628080618.522-1-juri.lelli@redhat.com> <20190628080618.522-6-juri.lelli@redhat.com> <20190628124553.GT3419@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190628124553.GT3419@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 28/06/19 14:45, Peter Zijlstra wrote: > On Fri, Jun 28, 2019 at 10:06:15AM +0200, Juri Lelli wrote: > > @@ -2154,7 +2154,7 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) > > cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css)); > > cs = css_cs(css); > > > > - mutex_lock(&cpuset_mutex); > > + percpu_down_read(&cpuset_rwsem); > > > > /* allow moving tasks into an empty cpuset if on default hierarchy */ > > ret = -ENOSPC; > > @@ -2178,7 +2178,7 @@ static int cpuset_can_attach(struct cgroup_taskset *tset) > > cs->attach_in_progress++; > > ret = 0; > > out_unlock: > > - mutex_unlock(&cpuset_mutex); > > + percpu_up_read(&cpuset_rwsem); > > return ret; > > } > > > > @@ -2188,9 +2188,9 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset) > > > > cgroup_taskset_first(tset, &css); > > > > - mutex_lock(&cpuset_mutex); > > + percpu_down_read(&cpuset_rwsem); > > css_cs(css)->attach_in_progress--; > > - mutex_unlock(&cpuset_mutex); > > + percpu_up_read(&cpuset_rwsem); > > } > > These are the only percpu_down_read()s introduced in this patch; are we > sure this is correct? Specifically, what serializes > ->attach_in_progress? No, I think it's wrong, sorry. I'll change to the write variant in next version. Thanks, Juri