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Fri, 10 Jul 2026 22:54:25 -0700 (PDT) Date: Sat, 11 Jul 2026 06:54:25 +0100 From: Matt Fleming To: Tejun Heo Cc: David Vernet , Andrea Righi , Changwoo Min , Johannes Weiner , Suren Baghdasaryan , Peter Zijlstra , Edward Adam Davis , Chen Ridong , Matt Fleming , sched-ext@lists.linux.dev, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@cloudflare.com Subject: Re: [PATCH cgroup/for-7.2-fixes] cgroup: Create the psimon kthread outside of cgroup_mutex Message-ID: References: <20260710100441.2653477-1-matt@readmodwrite.com> <20260710134945-psimon-fix-tj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260710134945-psimon-fix-tj@kernel.org> On Fri, Jul 10, 2026 at 01:49:45PM -1000, Tejun Heo wrote: > Matt, your reordering trades one deadlock for another: CLONE_INTO_CGROUP > forks grab cgroup_mutex inside the scx_fork_rwsem read section, so an > enable racing such a clone deadlocks the other way around. The fork has to > move out of the locked sections instead. Can you verify this fixes the > deadlock in your setup? Thanks for fixing this. I'll test this out ASAP and report back.