When hot-unplugging a 32-bit CPU on the parisc platform with "chcpu -d 1", I get the following kernel panic. Adding a check for !pwq prevents the panic. Kernel Fault: Code=26 (Data memory access rights trap) at addr 00000000 CPU: 1 PID: 21 Comm: cpuhp/1 Not tainted 6.8.0-rc1-32bit+ #1291 Hardware name: 9000/778/B160L IASQ: 00000000 00000000 IAOQ: 10446db4 10446db8 IIR: 0f80109c ISR: 00000000 IOR: 00000000 CPU: 1 CR30: 11dd1710 CR31: 00000000 IAOQ[0]: wq_update_pod+0x98/0x14c IAOQ[1]: wq_update_pod+0x9c/0x14c RP(r2): wq_update_pod+0x80/0x14c Backtrace: [<10448744>] workqueue_offline_cpu+0x1d4/0x1dc [<10429db4>] cpuhp_invoke_callback+0xf8/0x200 [<1042a1d0>] cpuhp_thread_fun+0xb8/0x164 [<10452970>] smpboot_thread_fn+0x284/0x288 [<1044d8f4>] kthread+0x12c/0x13c [<1040201c>] ret_from_kernel_thread+0x1c/0x24 Kernel panic - not syncing: Kernel Fault Signed-off-by: Helge Deller <deller@xxxxxx> --- diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 76e60faed892..dfeee7b7322c 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -4521,6 +4521,8 @@ static void wq_update_pod(struct workqueue_struct *wq, int cpu, wq_calc_pod_cpumask(target_attrs, cpu, off_cpu); pwq = rcu_dereference_protected(*per_cpu_ptr(wq->cpu_pwq, cpu), lockdep_is_held(&wq_pool_mutex)); + if (!pwq) + return; if (wqattrs_equal(target_attrs, pwq->pool->attrs)) return;
