From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f180.google.com (mail-pg1-f180.google.com [209.85.215.180]) (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 3F69821E0A2; Wed, 21 May 2025 23:52:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747871576; cv=none; b=XuHmnPu71lKxT8Eim59vgn2qJHqtOAfnqL1pG+kRRMIxioZkDORz9fHx27snOIjf4HSbd49oQeSlHXi+xKdErcsoJcHgYam1klnuhzOOUIncjgh2vlU74KI9nLnxcYdDatLg8hL0DFMs3CbUhgYbYfNZWwDRsxv5X0cy1R/as84= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747871576; c=relaxed/simple; bh=2qOpZHk8xt+g9fBaYg5YSi7uL4/V0iw7NjE1UcKvEVU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=X2g5/gsYeayJqcb09ch2bCQcy/sKLTECBwXC/kFE6bzqAzlYiTYgbKMfvaQNfKQhOQcBVLgWQXl6TR09QnHo701r3HxjK4Hh3qTyB4fAX4bKC2nQX7aXP6yRR28gZtD+SW9UhSlXzN3iIx0Qy9jdChvrmUy5U68ynzrBRqIp3Z0= 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=JiQkMwhF; arc=none smtp.client-ip=209.85.215.180 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="JiQkMwhF" Received: by mail-pg1-f180.google.com with SMTP id 41be03b00d2f7-b26d7ddbfd7so7631868a12.0; Wed, 21 May 2025 16:52:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1747871574; x=1748476374; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=tv8ABiZjTSsX7/N5+xUlPIqutk3RS4YiHeo90v4eMFk=; b=JiQkMwhFlCkAwj41xM4ImEnQxZ0j/DyFX1yWN3oQ8H9IW/vp2TjC/EqP1Inns03BOp 3w+boEftfVroDTwulutNsncH4ziKmUJJNcvfSU21DMNhbNIWkTCKVun5oIGIGyCIcKX+ Yiq+gontYZBR+N3mZvGiAO6lzAQax28/sjAx6UCuHfImoDv5khpxFxVwoWUymO/MQYJV YlFVEbL7hbkYViopLQK1twLZFzwJ7+zmVT1ifHSd0a7UsqyjAbZHrapumJ3TtSZHKfHd Z+SHOFjQTCoemADCXLMBmWYUmDiAbtv84SELAM2XgJILhOQ1iUxla5DyopDgpanS/Rp2 JsAA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747871574; x=1748476374; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=tv8ABiZjTSsX7/N5+xUlPIqutk3RS4YiHeo90v4eMFk=; b=U7+j0hVsBQBu7nFqrY9EEaIV8/U33YS4l3RW/ywNZpRQLDUoOYAD1Qw2CGKgp+GftR rfQ/DJqU+Gwt7uCA2fQiC2hqOitpBxqnRsAR9l/CI2GvzuLcDsgoTbIzJIFc1y9tx6tp 2BGoERW+0OL/uyRXVuXSwEwKtd/e/7saT6Fe6S4TcwXgo6/hZ5JGHeeZX5mDlCKAU9+J zQee0KaOtnlqJMIFZB3M6jwY+M4ORxwO8GrRTBoo7eNQCclNSqZko1Jjcln5sYJbfQSM JYdxLq16je0QCrnLx5OSDDd2ukwC8xCW0ERYrmStgJzLnZkz2GUxwyxrZJmolb/sunVE +31w== X-Forwarded-Encrypted: i=1; AJvYcCVPzSfbtH7E357LHPudtuUt6jFFNqG9wC2mS5L3Avrb1JjVEjL0dAgNNTdxX0gKjhLpASaYrY7XdQ==@vger.kernel.org, AJvYcCWOnWKLgzOyJQTkn2VYGADD8zePD7+CqijrAIeOBpnkyHjYabgRkfOg2azEQhj0nVKE7PePqgAt8gmAmikn@vger.kernel.org, AJvYcCWc4fkS46afkcMr04LlO2f8BbwfJNXprGzwaddbz7trFDoUbA+N9yf4r49Thvj7gnBlgQ8=@vger.kernel.org X-Gm-Message-State: AOJu0YyFOFCg7LOWGZE/PWqqUhGiMDNQncZMestqMGPy1oQoB9oxB4YH IZ9ClesFCB7M+6RC4ATvNoAzQcC/wfsSC0WQLcDQ0pp7mHVedUFwt7Jj X-Gm-Gg: ASbGnct0wl7MiSdtqF5AorbGB3u1stAF/UZdNVkpAf1J2IjtZE+FFxAr7OqaZa/n0EK Pt/096f0e8K1r6Yowr/vAgDrkN5pJRLWlRTNhDaGQ2qSnoWffacl7O/WXanp1XquQ8hjVc8yDru /Q8T2c2MDvRQ1XeO6Uea/gV+bzNSaiLCooVspeYg6j0Sc6JsJhN6PVo9TtfqwqmWyyQFr4ePr0I DF6BIlNrBoFeEPGWvtFOimCM2NhDs241CF4s8g8oPVlHH5iKgxxJlyh7+1RSKu7Qq2MuO+fgnoI muyr6reyDCH0W1H6AYVcxfCFu1qveiAJeg0jOi565NqUf495mQU4/LiqgeqDap2KUj+ZmJMJ/8C MSWb5nEscJrssoeNGMbSzFg== X-Google-Smtp-Source: AGHT+IEhRtWayz2wO/NANMbY77CLzICf7dbwLdeAITjL7G45qTo7ZKomEFbV0bEm0TWCBrjPtFfTWQ== X-Received: by 2002:a05:6a21:103:b0:1f5:7c6f:6c96 with SMTP id adf61e73a8af0-21621902a69mr37008453637.22.1747871574344; Wed, 21 May 2025 16:52:54 -0700 (PDT) Received: from [192.168.2.117] (c-67-188-127-15.hsd1.ca.comcast.net. [67.188.127.15]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-742a970c86asm10504612b3a.57.2025.05.21.16.52.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 May 2025 16:52:53 -0700 (PDT) Message-ID: <71f67d74-c2fa-4ca3-9bbc-7f239f24e97d@gmail.com> Date: Wed, 21 May 2025 16:52:52 -0700 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [OFFLIST PATCH 2/2] cgroup: use subsystem-specific rstat locks to avoid contention To: Shakeel Butt Cc: Klara Modin , Tejun Heo , Andrew Morton , Alexei Starovoitov , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Yosry Ahmed , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Vlastimil Babka , Sebastian Andrzej Siewior , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team References: <20250428174943.69803-1-inwardvessel@gmail.com> <20250428174943.69803-2-inwardvessel@gmail.com> <9151095d-98dc-4497-9a64-b2eb7f8f96ea@gmail.com> Content-Language: en-US From: JP Kobryn In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 5/21/25 4:50 PM, Shakeel Butt wrote: > On Wed, May 21, 2025 at 04:47:01PM -0700, JP Kobryn wrote: >> >> >> On 5/21/25 4:33 PM, Shakeel Butt wrote: >>> On Wed, May 21, 2025 at 04:23:44PM -0700, Shakeel Butt wrote: >>>> On Thu, May 22, 2025 at 12:23:44AM +0200, Klara Modin wrote: >>>>> Hi, >>>>> >>>>> On 2025-04-28 23:15:58 -0700, Shakeel Butt wrote: >>>>>> Please ignore this patch as it was sent by mistake. >>>>> >>>>> This seems to have made it into next: >>>>> >>>>> 748922dcfabd ("cgroup: use subsystem-specific rstat locks to avoid contention") >>>>> >>>>> It causes a BUG and eventually a panic on my Raspberry Pi 1: >>>>> >>>>> WARNING: CPU: 0 PID: 0 at mm/percpu.c:1766 pcpu_alloc_noprof (mm/percpu.c:1766 (discriminator 2)) >>>>> illegal size (0) or align (4) for percpu allocation >>>> >>>> Ok this config is without CONFIG_SMP and on such configs we have: >>>> >>>> typedef struct { } arch_spinlock_t; >>>> >>>> So, we are doing ss->rstat_ss_cpu_lock = alloc_percpu(0). >>>> >>>> Hmm, let me think more on how to fix this. >>>> >>> >>> I think following is the simplest fix: >>> >>> diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c >>> index 7dd396ae3c68..aab09495192e 100644 >>> --- a/kernel/cgroup/rstat.c >>> +++ b/kernel/cgroup/rstat.c >>> @@ -511,7 +511,10 @@ int __init ss_rstat_init(struct cgroup_subsys *ss) >>> int cpu; >>> if (ss) { >>> - ss->rstat_ss_cpu_lock = alloc_percpu(raw_spinlock_t); >>> + size_t size = sizeof(raw_spinlock_t) ?: 1; >>> + >>> + ss->rstat_ss_cpu_lock = __alloc_percpu(size, >>> + __alignof__(raw_spinlock_t)); >> >> Thanks for narrowing this one down so fast. Would this approach be more >> straightforward? >> >> if (ss) { >> #ifdef CONFIG_SMP >> ss->rstat_ss_cpu_lock = alloc_percpu(raw_spinlock_t); >> #endif >> >> Since on non-smp the lock functions are no-ops, leaving the ss cpu lock >> can perhaps be left NULL. I could include a comment as well explaining >> why. >> >>> if (!ss->rstat_ss_cpu_lock) >>> return -ENOMEM; > > Include this check and return -ENOMEM in the ifdef as well. Good call. I will get a patch out tonight. > >>> } >>