From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f175.google.com (mail-pl1-f175.google.com [209.85.214.175]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F2F3D3C1D48 for ; Thu, 20 Aug 2026 20:05:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.175 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787256308; cv=none; b=llGtBuLREARrsks86O/aH2FQk/bxRsMaot7SKdiBuLCq742HEZWPI8/GOERJA8JUcGpQu1S093gdklvePceejqlTzS/ai0t6qkiM/8Z2cvrSE3KHDLp/TysZtCs7bpQriBQf5obg+dAQ5ejPYLiEc4yokjQAXSUlLgmuw1hhLVU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787256308; c=relaxed/simple; bh=Aw/ofYSmMq/hCctkdEPZ9sneab2XTminwcfhlt6xz3g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gWhu+qy2B24Q8mAgNSeHvuNbejAWlXsq5u3kqQ9V3CXrKo+i/zoAfv9v3S92+u6u1Zo5uhEGrcdrrcg1o45XKI6CO+aALzwlg1zIsOQs34Mj9uQcNtD0YVVm3kfbiY+Tq1h0xeJ87wSZOvcJDEYiBtW6cZ+k85LKXhFFrkbG4sk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=CspOK5+8; arc=none smtp.client-ip=209.85.214.175 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="CspOK5+8" Received: by mail-pl1-f175.google.com with SMTP id d9443c01a7336-2caced6038eso1859615ad.0 for ; Thu, 20 Aug 2026 13:05:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1787256305; x=1787861105; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=W+ttLV2jMb/uOUdRDGthE1WHXT4FvT3P7ffiAV7gUtI=; b=CspOK5+8rXyfrhCiSkiXDpyCsuBHQUUYtm7NREaRjf48p5mXd9uLLSVBLzWt8FhdhD BvnzmGQPVmFq306Hsl5npy8DBYOYjaDGv5QFOnbTLAfQ5SNcTr75xEbDurQBBN9pbd6W YQllygYUNyDq0gU3ia79PycvUh1QerCAbwF1JMM/h45ovXt8JMnacYRtJasKMV7CZX5A PjvDVoo0AyrQVRddbTO7t1cDHdtYx6eY8d8IEqQRB1nLbL4w6yNSbXl3LJGEV70t4EZ7 b8UZGipq+Yu8zxh4/f+J7xwa5Ttrgq+wkiNocoCHGNbsIwnBFWz3uOL8B93MmQJMfb35 Jycw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787256305; x=1787861105; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=W+ttLV2jMb/uOUdRDGthE1WHXT4FvT3P7ffiAV7gUtI=; b=CQ4SBh7GZqSaQo0MSGdtfAQ/CpTYnjNybAsNoDOGdaC24XKuQDsSw+lHrmGhuwSrMN /ebgUCufPTXZeOPWHV22USQZ6FuZBvk9hA6BpsScfQD32UNuAgmzV/ahSrQsnhpWTSxO /lGZgCjHAdAT4+VN1qarW41DR+Wfo4v0hHJ5bVjmRumNPEp+j4v9tY7+tF0zKVdolJXG tTzjSjmSbjI08vJI35wOEt8wf9VV9IigLNLbEd/Bc4dwsmDRcT6lYmSUErMmgupN/dLb DDIkctwf+DHpLi7XftkhNtyMrHbhI44P8RgwKTwhF4/hnc0kpseGHykLEtXSXJHhCDT6 x8mw== X-Forwarded-Encrypted: i=1; AHgh+RqM6vwigTlwg0a5UjalDj5tz1ZzikMomST4wewUeGaG9vzxtBnqjY78znCDY2L5Zkaf34TZE376@vger.kernel.org X-Gm-Message-State: AFuF++nhrO4nYVa21fN+ZkMMRm67JpF0W/H2auweE3K16KsmQLmYeX63 s4XsgsF8Bb+vXHy89fLlE418oCfuAnNW0DlWiuW1W3EkFpFz6bOoUS2K X-Gm-Gg: AR+sD12MMK0k69RaX91A8PQKeBwh4ClAZ9izVV7va7jmWyLfdIFXRQLzRaGCkz0gZOf eh3xTvIkA012GV+4EXimV4rAbRuEEH5Ea81jA05iZ652MjJ8yHIQz0vaRhKsLyYnvG6fU/Kq2Cx fs35U+rVdhcDLdDDKWOQElU+vMRqDKAT6bHZ2mPrJAH4xsjeJ2Z0RxlKRvRGfrwbVyfSeg30A6G +a1XvnQ6Tma4QMIqf2/oeIM2qGg+W253m+s1dcmhyXp4UrxIK/i+k79/J9U1JOob6VaH/kgiPsp 84F21BlP1cAXJmfFpJI6aG3jYmBhh/YqtAeLNwz+GbXdKwtTHB5IY67IycgqszNIoihGSzAM1+9 riYtm/vWDNRPC4P8/ga2CXjZtDAPVNEKKsdBDRmSlESWyNPp+b3XJ9Mw675yiJGKDqvEw+tDTTv ms7NdOOjb5iEtr7jiApxIdjVFCE/3f5vtzNotJ28FP1FGmPUVfm2dMGBSNTRZSBoa7gdc6qo9mL BjlfoKW X-Received: by 2002:a17:902:fc48:b0:2cf:7ea3:7cf1 with SMTP id d9443c01a7336-2d61a078e1amr118047715ad.5.1787256305116; Thu, 20 Aug 2026 13:05:05 -0700 (PDT) Received: from devvm16600.scu0.facebook.com ([2a03:2880:9ff:6b::]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-327bf191821sm18740151eec.28.2026.08.20.13.05.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Aug 2026 13:05:04 -0700 (PDT) Date: Thu, 20 Aug 2026 13:05:01 -0700 From: Ziyang Men To: Tejun Heo 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: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Hi Tejun, On Wed, Aug 19, 2026 at 10:55:59AM -1000, Tejun Heo wrote: >Hello, > >On Tue, Aug 18, 2026 at 04:59:17PM -0700, Ziyang Men wrote: >> > > The bpf_cgroup_base_stat() takes an rstat spinlock_t, which can sleep on >> > > PREEMPT_RT. >> > >> > Is this actually required? This doesn't really make sense to me. Shouldn't >> > what SLEEPABLE mean change on RT kernels instead? >> >> Oh sorry, I didn't notice that. >> >> I might be wrong: this function calls the cputime_adjust(), which in turn >> acquires raw_spin_lock_irqsave(), so there would be NMI deadlock in the >> perf_event program. The __css_rstat_lock() take the spin_lock_irq() as well. So >> maybe a SLEEPABLE tag is still necessary? > >I think this is for BPF folks to answer. I don't think SLEEPABLE is needed >because of RT but yeah it wouldn't be safe to be called from nmi context. Ok I see, let's remove the SLEEPABLE for now. Thanks, Ziyang > >Thanks. > >-- >tejun