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b=rDGlgTnkXiuY9KvkfEDU0gx8sbwujdppo8tkrsV3bdTwU31apa0+t0Ah81F5pgQ4o O5lCPMGUzM7nGqbAXJFzs2iHmeIVyfxJVSiz/eaq/YnMEBGY+6gzw2PS0H8oJKYKht u0gdNsQIkCy6rGlZCHR1dd2XDCj9iLx5uffqQP1Lto8CRzyabZxkP1aBYDtB0Rgyed 7313XDwj+8BfZEtXXMM2+hHDaNK5P6LGprrtj90SLYEZc7wiNQpyvuJgmWDK4hMJBx WRx4zIG+BqHwyqf/VxvJiinFWQA8gZiqzU0lLb7ebYOGSJGAOwxCkyU+rhTrOEMXeE qS5Kyms4a3FDQ== Date: Wed, 21 May 2025 15:55:49 -1000 From: Tejun Heo To: JP Kobryn Cc: klarasmodin@gmail.com, shakeel.butt@linux.dev, 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 Subject: Re: [PATCH cgroup/for-6.16] cgroup: avoid per-cpu allocation of size zero rstat cpu locks Message-ID: References: <20250522013202.185523-1-inwardvessel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250522013202.185523-1-inwardvessel@gmail.com> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 42BB080005 X-Stat-Signature: ykxd869i18n4z6du9s6d4fenym5hfki6 X-Rspam-User: X-HE-Tag: 1747878952-856703 X-HE-Meta: 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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 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. > > Signed-off-by: JP Kobryn > Reported-by: Klara Modin > Fixes: 748922dcfabd ("cgroup: use subsystem-specific rstat locks to avoid contention") Applied to cgroup/for-6.16. Thanks. -- tejun