From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935838AbcKJRUg (ORCPT ); Thu, 10 Nov 2016 12:20:36 -0500 Received: from mx1.redhat.com ([209.132.183.28]:27224 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935772AbcKJRUe (ORCPT ); Thu, 10 Nov 2016 12:20:34 -0500 Date: Thu, 10 Nov 2016 18:20:31 +0100 From: Oleg Nesterov To: Thomas Gleixner , Petr Mladek Cc: Andy Lutomirski , Roman Pen , Andy Lutomirski , Peter Zijlstra , Ingo Molnar , Tejun Heo , "linux-kernel@vger.kernel.org" , Chunming Zhou , Alex Deucher Subject: [PATCH 1/1] kthread: don't abuse kthread_create_on_cpu() in __kthread_create_worker() Message-ID: <20161110172030.GB28264@redhat.com> References: <20161026141359.GA6893@redhat.com> <20161026155155.GA28832@redhat.com> <20161028161106.GA8933@redhat.com> <20161031200729.GA19430@redhat.com> <20161031200823.GC19430@redhat.com> <20161109172743.GB26446@redhat.com> <20161110171957.GA28264@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161110171957.GA28264@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Thu, 10 Nov 2016 17:20:34 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kthread_create_on_cpu() sets KTHREAD_IS_PER_CPU and kthread->cpu, this only makes sense if this kthread can be parked/unparked by cpuhp code. kthread workers never call kthread_parkme() so this has no effect. Change __kthread_create_worker() to simply call kthread_bind(task, cpu). The very fact that kthread_create_on_cpu() doesn't accept a generic fmt shows that it should not be used outside of smpboot.c. Now, the only reason we can not unexport this helper and move it into smpboot.c is that it sets kthread->cpu and struct kthread is not exported. And the only reason we can not kill kthread->cpu is that kthread_unpark() is used by drivers/gpu/drm/amd/scheduler/gpu_scheduler.c and thus we can not turn _unpark into kthread_unpark(struct smp_hotplug_thread *, cpu). Signed-off-by: Oleg Nesterov --- kernel/kthread.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index 01d2716..956495f 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -641,6 +641,7 @@ __kthread_create_worker(int cpu, unsigned int flags, { struct kthread_worker *worker; struct task_struct *task; + int node = -1; worker = kzalloc(sizeof(*worker), GFP_KERNEL); if (!worker) @@ -648,25 +649,17 @@ __kthread_create_worker(int cpu, unsigned int flags, kthread_init_worker(worker); - if (cpu >= 0) { - char name[TASK_COMM_LEN]; - - /* - * kthread_create_worker_on_cpu() allows to pass a generic - * namefmt in compare with kthread_create_on_cpu. We need - * to format it here. - */ - vsnprintf(name, sizeof(name), namefmt, args); - task = kthread_create_on_cpu(kthread_worker_fn, worker, - cpu, name); - } else { - task = __kthread_create_on_node(kthread_worker_fn, worker, - -1, namefmt, args); - } + if (cpu >= 0) + node = cpu_to_node(cpu); + task = __kthread_create_on_node(kthread_worker_fn, worker, + node, namefmt, args); if (IS_ERR(task)) goto fail_task; + if (cpu >= 0) + kthread_bind(task, cpu); + worker->flags = flags; worker->task = task; wake_up_process(task); -- 2.5.0