On Thu, 25 Jun 2015 16:44:13 -0500 Nathan Zimmer <nzim...@sgi.com> wrote:
> In kthread_create_on_node we set_cpus_allowed to cpu_all_mask > regardless of what the node is requested. > This seems incorrect. The `node' arg to kthread_create_on_node() refers to which node the task_struct and thread_info are allocated from. It doesn't refer to the CPUs upon which the thread is executed. See kthread_create_info.node and that gruesome task_struct.pref_node_fork thing. The kthread_create_on_node() kerneldoc explains this, in a confused way. It needs a s/-1/NUMA_NO_NODE/. I'm a bit surprised that kthread_create_on_node() futzes with the new thread's policy and cpumask after it has been created. Wouldn't it be simpler/faster to have the thread itself set these things while it's starting up? As to whether kthread_create_on_node() should bind the thread to that node's CPUs: unclear. drivers/thermal/intel_powerclamp.c:start_power_clamp() understands how kthread_create_on_node() works. I guess the code is OK as-is, but the documentation could be improved. Perfunctory effort: --- a/kernel/kthread.c~a +++ a/kernel/kthread.c @@ -246,7 +246,7 @@ static void create_kthread(struct kthrea * kthread_create_on_node - create a kthread. * @threadfn: the function to run until signal_pending(current). * @data: data ptr for @threadfn. - * @node: memory node number. + * @node: task and thread structures for the thread are allocated on this node * @namefmt: printf-style name for the thread. * * Description: This helper function creates and names a kernel @@ -254,7 +254,7 @@ static void create_kthread(struct kthrea * it. See also kthread_run(). * * If thread is going to be bound on a particular cpu, give its node - * in @node, to get NUMA affinity for kthread stack, or else give -1. + * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE. * When woken, the thread will run @threadfn() with @data as its * argument. @threadfn() can either call do_exit() directly if it is a * standalone thread for which no one will call kthread_stop(), or _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
