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From: Shakeel Butt Date: Mon, 2 Jun 2025 21:10:33 -0700 X-Gmail-Original-Message-ID: X-Gm-Features: AX0GCFvffCela-JHm8qWAxM6ah-WI8DA_Qa1VBMvvmS-zln7O7Hmg5RiXaTYm5E Message-ID: Subject: Re: [PATCH cgroup/for-6.16] cgroup: avoid per-cpu allocation of size zero rstat cpu locks To: Guenter Roeck 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: CC08B16000A X-Rspamd-Server: rspam09 X-Stat-Signature: 3kuzajystz97qjhxa4ahpcd51y9sxm7w X-HE-Tag: 1748923858-514235 X-HE-Meta: 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 OVB0XZaL XHvATm6iFHDk8fCpZmKRnuekROfCWxWpqLzwoF77dhT3ttT2ftyMeXRNC4Ld0MTq3miRnIhQPudA+8VtCqz7zMp1M8Mi8gLfJHMCUGdwhjSBMBmOmxuu/pWP3eoCOzJ5OIYe2KdCM//Me8kaCwTpWb6vYsJnnS4cp+0bp0Sc2mhdadAM0bGDEfk6q0PHiVgW0Z+M8zBQ8DzJsAQeMSjLsvL5oJzxxwIYd2IT4AYtN7C25FfzgE9Ip8/pxE0s+PW7mRttQP/paynPqMf9tLve/eHynW2VznbLyplwR 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 Mon, Jun 2, 2025 at 8:38=E2=80=AFPM Guenter Roeck w= rote: > > On Wed, May 21, 2025 at 06:32:02PM -0700, JP Kobryn wrote: > > Subsystem rstat locks are dynamically allocated per-cpu. It was discove= red > > that a panic can occur during this allocation when the lock size is zer= o. > > This is the case on non-smp systems, since arch_spinlock_t is defined a= s 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 pat= ch > 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/