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=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 4FD44C4707E for ; Fri, 21 May 2021 19:09:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 28A73613B6 for ; Fri, 21 May 2021 19:09:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237752AbhEUTKe (ORCPT ); Fri, 21 May 2021 15:10:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48762 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234847AbhEUTKc (ORCPT ); Fri, 21 May 2021 15:10:32 -0400 Received: from mail-pf1-x436.google.com (mail-pf1-x436.google.com [IPv6:2607:f8b0:4864:20::436]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D2AFC061574; Fri, 21 May 2021 12:09:09 -0700 (PDT) Received: by mail-pf1-x436.google.com with SMTP id x188so15591454pfd.7; Fri, 21 May 2021 12:09:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=s9Cp5133Mh+/zqJfqgPhMnUlYEemgkFwhti63wW8kUI=; b=fax43L1MPYF/lupgd8kkNEx9vH7DU3byne426xeI/wDqFC3pAht4iLEVX2hxPB/Hy6 lnX1ztghXBFoS4mXs7mm4yAxG6vRf/Ix9UsGb02wTErrT9igsZlqmNn3aeUuQslcnijG QO73zK6L9+9HCGZRpV5xJri82E4yZD4FiRm09B24nUAeamxTB/IVLjqAH9CinY+x/vcA LJCntK01UZI3qD+Xl9Zj2ikfOF4C1cdJIGhn/WVNWV+nyZMFgjxzvTNxrsbtpr7mdfCV 7nmx8smDbD3/C95oE6dvN3TPcHb+tVT58Y23ZstOyzHVsgFlcN00Ied5bnOrLEftTZDT k3wg== 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; bh=s9Cp5133Mh+/zqJfqgPhMnUlYEemgkFwhti63wW8kUI=; b=cWnbrElusloBJHHEmBoNqmj2Ma5CvNQ9YtK/rWJtKxRPyekZVm7HcvfLnywP0omAJt cVKJY0hFvNE8Vkmu+IQs20kozaBLD2qMbtDqkB0/grZcm1uS3GKiktr9Ffi545UjA9NZ tTLdgdCeNzacBhQWrZsWEcGSi/BQcjAr4IQViKWsIfVSYscU+gQXaKiVLVmqSpgCYqgZ BLWGIkjfNKMvtRI8m3HnhEEmtDsNbUNDdG5+2x9sk3+/7X9vIXlKbw/bCYrxUlgcdW2y 3MOfgUOANt99wD81yul+sf2OnGJmhXFA2pRlrbDs0GED+DafnZ/ilW65ydTm9YaUKt1O rgIQ== X-Gm-Message-State: AOAM531tZZ0KJQX7tvhtUK62jyBke1uztgmiGJodeZMBopBN5feEQtFr YjLihGp7egdbdTzBWsMlblI= X-Google-Smtp-Source: ABdhPJzMe31162py2dDnpEKn8gX+Saka8i654M1Dicx1XmDSbBCA5qpkLnHZ+G8eWEd6cH4sshlYXA== X-Received: by 2002:a63:1d2:: with SMTP id 201mr205962pgb.3.1621624148325; Fri, 21 May 2021 12:09:08 -0700 (PDT) Received: from gmail.com ([2601:600:8500:5f14:d627:c51e:516e:a105]) by smtp.gmail.com with ESMTPSA id 6sm4911081pfx.117.2021.05.21.12.09.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 May 2021 12:09:07 -0700 (PDT) Date: Fri, 21 May 2021 12:06:07 -0700 From: Andrei Vagin To: Peter Oskolkov Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Paul Turner , Ben Segall , Peter Oskolkov , Joel Fernandes , Andrew Morton , Andrei Vagin , Jim Newsome Subject: Re: [RFC PATCH v0.1 4/9] sched/umcg: implement core UMCG API Message-ID: References: <20210520183614.1227046-1-posk@google.com> <20210520183614.1227046-5-posk@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline In-Reply-To: <20210520183614.1227046-5-posk@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 20, 2021 at 11:36:09AM -0700, Peter Oskolkov wrote: > @@ -67,7 +137,75 @@ SYSCALL_DEFINE4(umcg_register_task, u32, api_version, u32, flags, u32, group_id, > */ > SYSCALL_DEFINE1(umcg_unregister_task, u32, flags) > { > - return -ENOSYS; > + struct umcg_task_data *utd; > + int ret = -EINVAL; > + > + rcu_read_lock(); > + utd = rcu_dereference(current->umcg_task_data); > + > + if (!utd || flags) > + goto out; > + > + task_lock(current); > + rcu_assign_pointer(current->umcg_task_data, NULL); > + task_unlock(current); > + > + ret = 0; > + > +out: > + rcu_read_unlock(); > + if (!ret && utd) { > + synchronize_rcu(); synchronize_rcu is expensive. Do we really need to call it here? Can we use kfree_rcu? Where is task->umcg_task_data freed when a task is destroyed? > + kfree(utd); > + } > + return ret; > +} > +