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([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-747afeab0c4sm8454850b3a.48.2025.06.02.21.26.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Jun 2025 21:26:29 -0700 (PDT) Message-ID: <6aec381e-d548-4b09-ac8b-4b63e1dd1133@roeck-us.net> Date: Mon, 2 Jun 2025 21:26:27 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH cgroup/for-6.16] cgroup: avoid per-cpu allocation of size zero rstat cpu locks To: Shakeel Butt Cc: JP Kobryn , tj@kernel.org, klarasmodin@gmail.com, yosryahmed@google.com, mkoutny@suse.com, hannes@cmpxchg.org, akpm@linux-foundation.org, linux-mm@kvack.org, cgroups@vger.kernel.org, kernel-team@meta.com References: <20250522013202.185523-1-inwardvessel@gmail.com> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAmgrMyQFCSbODQkACgkQyx8mb86fmYGcWRAA oRwrk7V8fULqnGGpBIjp7pvR187Yzx+lhMGUHuM5H56TFEqeVwCMLWB2x1YRolYbY4MEFlQg VUFcfeW0OknSr1s6wtrtQm0gdkolM8OcCL9ptTHOg1mmXa4YpW8QJiL0AVtbpE9BroeWGl9v 2TGILPm9mVp+GmMQgkNeCS7Jonq5f5pDUGumAMguWzMFEg+Imt9wr2YA7aGen7KPSqJeQPpj onPKhu7O/KJKkuC50ylxizHzmGx+IUSmOZxN950pZUFvVZH9CwhAAl+NYUtcF5ry/uSYG2U7 DCvpzqOryJRemKN63qt1bjF6cltsXwxjKOw6CvdjJYA3n6xCWLuJ6yk6CAy1Ukh545NhgBAs rGGVkl6TUBi0ixL3EF3RWLa9IMDcHN32r7OBhw6vbul8HqyTFZWY2ksTvlTl+qG3zV6AJuzT WdXmbcKN+TdhO5XlxVlbZoCm7ViBj1+PvIFQZCnLAhqSd/DJlhaq8fFXx1dCUPgQDcD+wo65 qulV/NijfU8bzFfEPgYP/3LP+BSAyFs33y/mdP8kbMxSCjnLEhimQMrSSo/To1Gxp5C97fw5 3m1CaMILGKCmfI1B8iA8zd8ib7t1Rg0qCwcAnvsM36SkrID32GfFbv873bNskJCHAISK3Xkz qo7IYZmjk/IJGbsiGzxUhvicwkgKE9r7a1rOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAmgrMyQFCSbODQkACgkQyx8mb86fmYHlgg/9 H5JeDmB4jsreE9Bn621wZk7NMzxy9STxiVKSh8Mq4pb+IDu1RU2iLyetCY1TiJlcxnE362kj njrfAdqyPteHM+LU59NtEbGwrfcXdQoh4XdMuPA5ADetPLma3YiRa3VsVkLwpnR7ilgwQw6u dycEaOxQ7LUXCs0JaGVVP25Z2hMkHBwx6BlW6EZLNgzGI2rswSZ7SKcsBd1IRHVf0miwIFYy j/UEfAFNW+tbtKPNn3xZTLs3quQN7GdYLh+J0XxITpBZaFOpwEKV+VS36pSLnNl0T5wm0E/y scPJ0OVY7ly5Vm1nnoH4licaU5Y1nSkFR/j2douI5P7Cj687WuNMC6CcFd6j72kRfxklOqXw zvy+2NEcXyziiLXp84130yxAKXfluax9sZhhrhKT6VrD45S6N3HxJpXQ/RY/EX35neH2/F7B RgSloce2+zWfpELyS1qRkCUTt1tlGV2p+y2BPfXzrHn2vxvbhEn1QpQ6t+85FKN8YEhJEygJ F0WaMvQMNrk9UAUziVcUkLU52NS9SXqpVg8vgrO0JKx97IXFPcNh0DWsSj/0Y8HO/RDkGXYn FDMj7fZSPKyPQPmEHg+W/KzxSSfdgWIHF2QaQ0b2q1wOSec4Rti52ohmNSY+KNIW/zODhugJ np3900V20aS7eD9K8GTU0TGC1pyz6IVJwIE= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: DBB2C180008 X-Stat-Signature: dmk6ejj48ysqrkowkweizk7z8t5njq51 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1748924790-723328 X-HE-Meta: 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 WvCoq1S2 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/2/25 21:10, Shakeel Butt wrote: > On Mon, Jun 2, 2025 at 8:38 PM Guenter Roeck wrote: >> >> On Wed, May 21, 2025 at 06:32:02PM -0700, JP Kobryn wrote: >>> Subsystem rstat locks are dynamically allocated per-cpu. It was discovered >>> that a panic can occur during this allocation when the lock size is zero. >>> This is the case on non-smp systems, since arch_spinlock_t is defined as an >>> empty struct. Prevent this allocation when !CONFIG_SMP by adding a >>> pre-processor conditional around the affected block. >>> >> >> It may be defined as empty struct, but it is still dereferenced. This patch >> is causing crashes on non-SMP systems such as xtensa, m68k, or with x86 >> non-SMP builds. >> > > Does this still happen with the following patch? > > https://lore.kernel.org/20250528235130.200966-1-inwardvessel@gmail.com/ I guess that should fix it. Sorry, I had not seen/found that patch. Guenter