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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 42F7FC433F5 for ; Tue, 14 Sep 2021 16:51:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 25F4A60E9B for ; Tue, 14 Sep 2021 16:51:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229464AbhINQw7 (ORCPT ); Tue, 14 Sep 2021 12:52:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44276 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229960AbhINQw7 (ORCPT ); Tue, 14 Sep 2021 12:52:59 -0400 Received: from mail-lf1-x134.google.com (mail-lf1-x134.google.com [IPv6:2a00:1450:4864:20::134]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F98AC061762 for ; Tue, 14 Sep 2021 09:51:41 -0700 (PDT) Received: by mail-lf1-x134.google.com with SMTP id k13so30218853lfv.2 for ; Tue, 14 Sep 2021 09:51:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=SjSQE15uKcrKRnQuwXqswKvc6fyo2MaxbsLWDKYQ4RY=; b=DO2pmRkTjsKJiTLCol77A0gNdGwgoMm2ep17W0C9mucS7ff/YCFdWbSHs2ErU6fhPu YUzTMjtCt8PLZc31uy2O+m8HW0pswP6pDCYl1qQiX9gB0CrYRIo9fUGPJbMM1HH3oalL HrPPpKM1rd1RoAq3HwZSYyx1VeRlEHHMYTGmLqu3hR00cj54+41Zv283qlza8SvPKvAZ tanO7zyNiVbf6CE/ZEjUZBkJjLVMDxd2b13weLL0PMmqUaggV+EuLDXmU/dD1sz0bLCz uSjKQVgCiuuPHwY7GioyHiEl0/b3gCsHQ4b6BfK75gOdCzG7324Z83iVL+FENUbnD4e/ a5jQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=SjSQE15uKcrKRnQuwXqswKvc6fyo2MaxbsLWDKYQ4RY=; b=E4FkIZnvrt63+iXrOCLZZFb990Emg0975AaPV/VYCjA3K8YopxF3eYK2zcmkrbgdue ZTzyqv9h2aly9PACq4YVyN601kXuMqjQVNuLN0nN/mxiOkp44sKkWguH1w4wSAWv4u33 M5jd+AiygaEDxMb9PjRd3/UqHYsibWvLegfke8mdzXrEw5zrmRaSMaV9UpH/z65U1Ps+ GE4Mpy39Y9yTXghJ8vGfrJovs8/h2C2Op6ukydUo6r9W3LozcBwwZr0if8Lj/+MR/YlL eRERZcpZU982faGV/uvzFFsnb8um3/64LpWJSxbWoS/Evugz9jCIR6p4W6yssjQssbBF p+wQ== X-Gm-Message-State: AOAM533ZGXaz2JYo0BLGUh74gJ8NW45XRzXeqRxL09VDxePaoOi2FIYV vjV5GD8hPjJnwAUC7bskGpekg4j5VX/4gqGVyduEqA== X-Google-Smtp-Source: ABdhPJw8kEH9jiZmIM3Ry3MTSBK9jdpUAOYp3qY4qOZ2T79bacMn9Mr8HKuTARFGh+rP4G9Wpd+ptyNvmJGYAEKk6BQ= X-Received: by 2002:ac2:4e98:: with SMTP id o24mr13877402lfr.295.1631638299813; Tue, 14 Sep 2021 09:51:39 -0700 (PDT) MIME-Version: 1.0 References: <20210908184905.163787-1-posk@google.com> <20210908184905.163787-4-posk@google.com> In-Reply-To: From: Peter Oskolkov Date: Tue, 14 Sep 2021 09:51:28 -0700 Message-ID: Subject: Re: [PATCH 3/4 v0.5] sched/umcg: RFC: implement UMCG syscalls To: Jann Horn Cc: Peter Oskolkov , Peter Zijlstra , Ingo Molnar , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Paul Turner , Ben Segall , Andrei Vagin , Thierry Delisle Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Wed, Sep 8, 2021 at 6:40 PM Jann Horn wrote: [...] > I think umcg_idle_loop() should never be called from scheduler > callbacks (meaning umcg_wq_worker_running()), only from UMCG syscalls. I'm moving umcg_wq_worker_running() out of core.c/sched_update_worker() and into /kernel/entry/common.c/exit_to_user_mode_loop() (and will rename the function appropriately). It seems rescheduling/sleeping there is fine. I'm not yet sure if this is all that is needed to deal with UMCG_TF_PREEMPTED flag; but I don't expect to see any locks held when the task truly returns to the userspace. Maybe I'll need to set TIF_NOTIFY_RESUME in sched_update_worker()... [...]