This is a note to let you know that I've just added the patch titled workqueue: make sysfs of unbound kworker cpumask more clever to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: workqueue-make-sysfs-of-unbound-kworker-cpumask-more.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit b9d3c0f269a4a3578b0f5960b7d7fc0a9753d458 Author: Menglong Dong <imagedong@xxxxxxxxxxx> Date: Sun Oct 17 20:04:02 2021 +0800 workqueue: make sysfs of unbound kworker cpumask more clever [ Upstream commit d25302e46592c97d29f70ccb1be558df31a9a360 ] Some unfriendly component, such as dpdk, write the same mask to unbound kworker cpumask again and again. Every time it write to this interface some work is queue to cpu, even though the mask is same with the original mask. So, fix it by return success and do nothing if the cpumask is equal with the old one. Signed-off-by: Mengen Sun <mengensun@xxxxxxxxxxx> Signed-off-by: Menglong Dong <imagedong@xxxxxxxxxxx> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 885d4792abdfc..77e6964ae1a99 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -5302,9 +5302,6 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) int ret = -EINVAL; cpumask_var_t saved_cpumask; - if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) - return -ENOMEM; - /* * Not excluding isolated cpus on purpose. * If the user wishes to include them, we allow that. @@ -5312,6 +5309,15 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) cpumask_and(cpumask, cpumask, cpu_possible_mask); if (!cpumask_empty(cpumask)) { apply_wqattrs_lock(); + if (cpumask_equal(cpumask, wq_unbound_cpumask)) { + ret = 0; + goto out_unlock; + } + + if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) { + ret = -ENOMEM; + goto out_unlock; + } /* save the old wq_unbound_cpumask. */ cpumask_copy(saved_cpumask, wq_unbound_cpumask); @@ -5324,10 +5330,11 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) if (ret < 0) cpumask_copy(wq_unbound_cpumask, saved_cpumask); + free_cpumask_var(saved_cpumask); +out_unlock: apply_wqattrs_unlock(); } - free_cpumask_var(saved_cpumask); return ret; }