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[34.228.114.98]) by smtp.gmail.com with ESMTPSA id af79cd13be357-93be0ccabecsm172276485a.6.2026.09.18.08.48.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2026 08:48:37 -0700 (PDT) Date: Fri, 18 Sep 2026 15:48:20 +0000 Message-ID: From: Josef Bacik To: sashiko-reviews@lists.linux.dev Cc: linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, rcu@vger.kernel.org Subject: Re: [PATCH RFC v4 02/13] rcu-tasks: Add a Tasks RCU implementation for reader-marked trampolines In-Reply-To: <20260918151031.2E0941F000FF@smtp.kernel.org> References: <20260918-b4-rcu-tasks-preempt-qs-v4-0-63f0e9d69661@toxicpanda.com> <20260918-b4-rcu-tasks-preempt-qs-v4-2-63f0e9d69661@toxicpanda.com> <20260918151031.2E0941F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Fri, 18 Sep 2026 15:10:30 +0000, sashiko-bot@kernel.org wrote: > However, the per-cpu rtp_exit_list list head cannot be statically > initialized and is dynamically initialized via cblist_init_generic() from > a core_initcall. Since core_initcalls are executed much later by the > kernel_init thread, any preemption before that phase will attempt to > list_add() to a zero-initialized (null) rtp_exit_list. No, cblist_init_generic() is not run from the core_initcall. It is run from rcu_init() -> tasks_cblist_init_generic(), which start_kernel() calls with interrupts still disabled (the function asserts as much) and well before its local_irq_enable(). The core_initcall only spawns the grace-period kthread. So the per-CPU rtp_exit_list heads exist before the first interrupt can be taken, let alone an irq-exit preemption; the classic flavor's exit_tasks_rcu_start() already depends on the same ordering for the same list. Thanks, Josef