From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D02C93A3E7A; Tue, 18 Aug 2026 17:16:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787073386; cv=none; b=bIDsvuStgGB5SJ5w0jNOkTuih/sr2zdAjMEhhLcrNMT6vAKeF4WU8aoSYzJGgvJbbD9pn8X3up/PMXjoGU/zKKYjG33o6OyxTT258tpZz357HYXPdqTkno68YI8QW6BKOrC5Uie68MA+YKRAtYAnKbaXglCWv5wxCnjWWRG3iMs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787073386; c=relaxed/simple; bh=VuZPMpnS8NPFkrTAMXBBESwpuMUlXCj215pqsSFrG/M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kxMre0Y35mjHWmhbRzzFI2RelMPK7yB6BVg419dCZ5OK94gLQmM+ETossZPFEa41iPG7Ysrer8BUSs8ee5vtyQ8D4UKC4fLNxEV/z+/3LlvBkiuE2/OtgS4J1C2hMyHSWtsjxq5ErSIno+PBppTKliwfKHGjr5zJfGFt8dhpu0g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Dwj9K7Gr; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Dwj9K7Gr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C5F71F000E9; Tue, 18 Aug 2026 17:16:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787073385; bh=WH4WPT0ROVvQC1ncoMRSxYGxqkEaGEutzNvZ3MuoB50=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Dwj9K7GrS7h3gJoBG73WZViEQ1tJMFfDLxokVxyhIUHAoPvnjzThLYQPoyPJA+C4q lfIpTtwR5kHHouT5f3OKvmikf72y13sh1gc+XIlnC2xFPI6hCyMEx8+KqN5xgq5lwT cmWmc4/elKc5xervIkDqxvqAxck9NekHjLna/oIqYri83CapDJcXrtxWOZY88awGsl 5XKR5lBlQ3xu3PfU2mZssA4Em5cwSP65MbuLdpz9zrJEOQRZUp4qrpjFdlUL/EHouo LipwY564W/lHwnUdavXMuJ5RLaXXENjrJi9uljd09c67s1uVYGaS+cBJFcYagB2dbo eQSU7RsMdBWkg== Date: Tue, 18 Aug 2026 07:16:24 -1000 From: Tejun Heo To: Ziyang Men Cc: Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Shuah Khan , kernel-team@meta.com, Ingo Molnar , Peter Zijlstra , Vincent Guittot , Ben Segall , Dietmar Eggemann , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Roman Gushchin , Shakeel Butt , JP Kobryn , bpf@vger.kernel.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] cgroup: add BPF kfuncs to read a cpu cgroup's stats Message-ID: References: <20260818002450.3071325-1-ziyang.meme@gmail.com> <20260818002450.3071325-2-ziyang.meme@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260818002450.3071325-2-ziyang.meme@gmail.com> On Mon, Aug 17, 2026 at 05:24:49PM -0700, Ziyang Men wrote: > +++ b/kernel/cgroup/bpf_cpu.c Probably not the best file name. bpf_cgroup.c or maybe just put it in cgroup.c? > +/** > + * bpf_css_to_task_group - Cast a CPU controller css to its task group > + * @css: CPU controller css > + * > + * Must be called under RCU. > + * A C cast does not give the verifier a task_group pointer. This kfunc > + * preserves the task_group and per-CPU types needed to read cfs_rq. The fact that this is used for per-CPU types now probably won't age well if this grows more usages in the future. > + * > + * Return: The task group, or NULL if @css belongs to another controller. > + */ > +__bpf_kfunc struct task_group * > +bpf_css_to_task_group(struct cgroup_subsys_state *css) > +{ > + if (css->ss != &cpu_cgrp_subsys) unlikely()? > + return NULL; > + > + /* task_group embeds css at offset zero. */ > + return (struct task_group *)css; container_of()? > +/** > + * bpf_css_flush_rstat - Flush a cgroup subsystem's rstat data > + * @css: cgroup subsystem state to flush > + */ > +__bpf_kfunc void bpf_css_flush_rstat(struct cgroup_subsys_state *css) > +{ > + css_rstat_flush(css); > +} Why is this necessary? Isn't css_rstat_flush() already exposed as a kfunc? > +/** > + * bpf_cgroup_base_stat - Read a cgroup's base statistics > + * @cgrp: cgroup to read from > + * @out: zero-initialized output in nanoseconds > + * > + * CPU time is adjusted as for cpu.stat. > + */ > +__bpf_kfunc void bpf_cgroup_base_stat(struct cgroup *cgrp, > + struct cgroup_base_stat *out) > +{ > + if (cgroup_parent(cgrp)) { > + __css_rstat_lock(&cgrp->self, -1); > + *out = cgrp->bstat; > + cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime, > + &out->cputime.utime, &out->cputime.stime); > + __css_rstat_unlock(&cgrp->self, -1); > + } else { > + root_cgroup_cputime(out); > + } > +} > + > +__bpf_kfunc_end_defs(); > + > +BTF_KFUNCS_START(bpf_rstat_common_kfunc_ids) > +BTF_ID_FLAGS(func, bpf_css_flush_rstat, KF_SLEEPABLE) > +BTF_ID_FLAGS(func, bpf_cgroup_base_stat, KF_SLEEPABLE) Why are these SLEEPABLE? Thanks. -- tejun