__padata_remove_cpu clears the offlined CPU from the usable masks after padata_alloc_pd has initialized pd->cpu, which means pd->cpu could be initialized to this CPU, causing padata to wait indefinitely for the next job in padata_get_next. Make the usable masks reflect the offline CPU when they're established in padata_setup_cpumasks so pd->cpu is initialized properly. Fixes: 6fc4dbcf0276 ("padata: Replace delayed timer with immediate workqueue in padata_reorder") Signed-off-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx> Cc: linux-crypto@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx --- Hi, one more edge case. All combinations of CPUs among parallel_cpumask, serial_cpumask, and CPU hotplug have now been tested in a 4-CPU VM, and an 8-CPU VM has run with random combinations of these settings for over an hour. kernel/padata.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/kernel/padata.c b/kernel/padata.c index 01460ea1d160..c1002ac4720c 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -702,17 +702,27 @@ static int __padata_remove_cpu(struct padata_instance *pinst, int cpu) struct parallel_data *pd = NULL; if (cpumask_test_cpu(cpu, cpu_online_mask)) { + cpumask_var_t pcpu, cbcpu; + __padata_stop(pinst); - pd = padata_alloc_pd(pinst, pinst->cpumask.pcpu, - pinst->cpumask.cbcpu); + /* + * padata_alloc_pd uses cpu_online_mask to get the usable + * masks, but @cpu hasn't been removed from it yet, so use + * temporary masks that exclude @cpu so the usable masks show + * @cpu as offline for pd->cpu's initialization. + */ + cpumask_copy(pcpu, pinst->cpumask.pcpu); + cpumask_copy(cbcpu, pinst->cpumask.cbcpu); + cpumask_clear_cpu(cpu, cbcpu); + cpumask_clear_cpu(cpu, pcpu); + + pd = padata_alloc_pd(pinst, pcpu, cbcpu); if (!pd) return -ENOMEM; padata_replace(pinst, pd); - cpumask_clear_cpu(cpu, pd->cpumask.cbcpu); - cpumask_clear_cpu(cpu, pd->cpumask.pcpu); if (padata_validate_cpumask(pinst, pd->cpumask.pcpu) && padata_validate_cpumask(pinst, pd->cpumask.cbcpu)) __padata_start(pinst); -- 2.22.0