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 81563C4332F for ; Mon, 12 Dec 2022 18:03:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231971AbiLLSDe (ORCPT ); Mon, 12 Dec 2022 13:03:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59544 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232946AbiLLSD3 (ORCPT ); Mon, 12 Dec 2022 13:03:29 -0500 Received: from mail-pj1-x102c.google.com (mail-pj1-x102c.google.com [IPv6:2607:f8b0:4864:20::102c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 43AE410F8; Mon, 12 Dec 2022 10:03:27 -0800 (PST) Received: by mail-pj1-x102c.google.com with SMTP id fy4so640520pjb.0; Mon, 12 Dec 2022 10:03:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=0bNS+IL9G3jZOP7BFktoG/NDExOtM0WC4ksPDn3Pgns=; b=FfOYp2sZIXs73LIMVCORQIqZ6qqbyX+ljz7sbQviFlaniHEWIw7037gUNEEVVOPLMI O2k+KMzV11Yn2XmUCBRh4V3iz16+DyYEfq7a5rYtnxdeO9tlPwEBkh+r3Dfpy1VgC2g6 3OlNaAU18JTVwgLB2N/HxnVqD0/abqpNs/rGJLlZg4LUnxRlx/lF4J5kCYk5Ea38Y/Dd hSbN9MCayy3VlcrJevJX5S34afpV/89JPqLwg4zotC/KgSr3nHG8fTg99bCTynhjNogM M/cP4yn8ceZTKwMv94y3ZjOtnPYh4cr+jLsH+WUEd2rLUhIC+/BMhTdPf0e/3A5LvB4f z1Mg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=0bNS+IL9G3jZOP7BFktoG/NDExOtM0WC4ksPDn3Pgns=; b=lkmXD8aI3ZBjDUm/buBQL1+B60POvMU+C2AJkVn+3eKp4tpQVccCsU/cCgQWPB0Wur EB1+1o4te/TGp4l7H/TIop7YNEbLu7JY84VTsZODVURUc3Tl6cTzcibvICM6uSgCLEh3 lGIub4isoZIn2Xo0URlmHK5XDQW5sqCs09AevrK1XKEWBbefy+0wy5ivlQRjnz+8zg6w /NG7/l6WgIiiKXDW75aPPiwCMSBNIS9nLoa1GRUN81Bw4Pstkk/E9HmlEz9nHMuBEIc2 u+6CCTTi1YkhvDeBSYioVMBsISomL0U1b2pauWGuADUSIYtmmVpZwpfy1JtJGeGD1nph IhfQ== X-Gm-Message-State: ANoB5plg/JNA8E43+9Vev8EXpyAdFstgiIjJn9Oi9U+rkCT6kOLYc8/M TdTagXK5sv5wWOT0GW0vV5c= X-Google-Smtp-Source: AA0mqf5HLf6ebynEh5N3JXUZHOPS3NmjgLrmyBtErYQjpDTSkA76dHjV7qiQXHjHEk+t/hriWj4nAg== X-Received: by 2002:a05:6a20:690b:b0:a7:89fd:884c with SMTP id q11-20020a056a20690b00b000a789fd884cmr24471389pzj.11.1670868206530; Mon, 12 Dec 2022 10:03:26 -0800 (PST) Received: from localhost ([2620:10d:c090:400::5:9159]) by smtp.gmail.com with ESMTPSA id x2-20020a628602000000b00576d4d69909sm6113443pfd.8.2022.12.12.10.03.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Dec 2022 10:03:26 -0800 (PST) Sender: Tejun Heo Date: Mon, 12 Dec 2022 08:03:24 -1000 From: Tejun Heo To: Peter Zijlstra Cc: torvalds@linux-foundation.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, joshdon@google.com, brho@google.com, pjt@google.com, derkling@google.com, haoluo@google.com, dvernet@meta.com, dschatzberg@meta.com, dskarlat@cs.cmu.edu, riel@surriel.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 04/31] sched: Allow sched_cgroup_fork() to fail and introduce sched_cancel_fork() Message-ID: References: <20221130082313.3241517-1-tj@kernel.org> <20221130082313.3241517-5-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, Dec 12, 2022 at 12:13:31PM +0100, Peter Zijlstra wrote: > On Tue, Nov 29, 2022 at 10:22:46PM -1000, Tejun Heo wrote: > > A new sched_clas needs a bit more control over forking. This patch makes the > ^ > (insufficient s's) Will update. > > following changes: > > > > * Add sched_cancel_fork() which is called if fork fails after sched_fork() > > succeeds so that the preparation can be undone. > > > > * Allow sched_cgroup_fork() to fail. > > > > Neither is used yet and this patch shouldn't cause any behavior changes. > > Fails to explain why this would be needed and why that would be a good > thing. IOW, total lack of justification. This is because sched_ext calls out to BPF scheduler's prepare_enable() operation to prepare the task. The operation is allowed to fail (e.g. it might need to allocate something which can fail), so we need a way back back out of it. Thanks. -- tejun