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Fri, 22 Nov 2024 01:35:28 -0800 Resent-From: Krister Johansen Resent-Date: Fri, 22 Nov 2024 01:35:28 -0800 Resent-Message-ID: <20241122093528.GC7186@templeofstupid.com> Resent-To: rcu@vger.kernel.org Date: Fri, 22 Nov 2024 00:46:22 -0800 From: Krister Johansen To: "Paul E. McKenney" , Neeraj Upadhyay , stable@vger.kernel.org Cc: Frederic Weisbecker , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , rcu@vger.kernel.org, David Reaver Subject: [PATCH stable 5.15/5.10 0/2] rcu-tasks: Idle tasks on offline CPUs are in quiescent states Message-ID: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline Paul, Neeraj, and Stable Team: I've run into a case with rcu_tasks_postscan where the warning introduced as part of 46aa886c4("rcu-tasks: Fix IPI failure handling in trc_wait_for_one_reader") is getting triggered when trc_wait_for_one_reader sends an IPI to a CPU that is offline. This is occurring on a platform that has hotplug slots available but not populated. I don't believe the bug is caused by this change, but I do think that Paul's commit that confines the postscan operation to just the active CPUs would help prevent this from happening. Would the RCU maintainers be amenable to having this patch backported to the 5.10 and 5.15 branches as well? I've attached cherry-picks of the relevant commits to minimize the additional work needed. Thanks, -K Paul E. McKenney (1): rcu-tasks: Idle tasks on offline CPUs are in quiescent states kernel/rcu/tasks.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)