On Wed, 2023-12-20 at 16:13 +0100, Frederic Weisbecker wrote: > Le Wed, Dec 20, 2023 at 04:24:35PM +0800, Z qiang a écrit : > > > > > > > In the rcutree_report_cpu_dead(), the rcuog kthreads may also be > > wakeup in > > do_nocb_deferred_wakeup(), if the rcuog kthreads is rt-fifo and > > wakeup happen, > > the rt_period_active is set 1 and enqueue hrtimer to offline CPU in > > do_start_rt_bandwidth(), > > after that, we invoke swake_up_one_online() send ipi to online CPU, > > due to the > > rt_period_active is 1, the rt-bandwith hrtimer will not enqueue to > > online CPU. > > any thoughts? > > Duh, you're right, that one too. How many more? This hrtimer > situation is scary... > > Thanks. I encountered the issue pointed out by Z Qiang on kernel-6.6, which cause RT tasks on the CPU to never be scheduled, leading to a system reboot. It triggered the WARN_ON_ONCE(!base->cpu_base->online) introduced in [PATCH 1/3]. Below is the call trace: Call trace: enqueue_hrtimer+0x7c/0xf8 hrtimer_start_range_ns+0x2b8/0x300 enqueue_task_rt+0x298/0x3f0 enqueue_task+0x94/0x188 ttwu_do_activate+0xb4/0x27c try_to_wake_up+0x2d8/0x79c wake_up_process+0x18/0x28 __wake_nocb_gp+0x80/0x1a0 do_nocb_deferred_wakeup_common+0x3c/0xcc rcu_report_dead+0x68/0x1ac cpuhp_report_idle_dead+0x48/0x9c do_idle+0x288/0x294 cpu_startup_entry+0x34/0x3c secondary_start_kernel+0x138/0x158
