From 8fb9dcbdc3619741c10c573199d804161c34c89a Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 29 Nov 2016 18:51:10 +0100 Subject: [PATCH] kthread: Don't abuse kthread_create_on_cpu() in __kthread_create_worker() 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 Tested-by: Petr Mladek Acked-by: Peter Zijlstra (Intel) Reviewed-by: Petr Mladek Cc: Chunming Zhou Cc: Roman Pen Cc: Andy Lutomirski Cc: Tejun Heo Cc: Andy Lutomirski Cc: Alex Deucher Cc: Andrew Morton Link: http://lkml.kernel.org/r/20161129175110.GA5342@redhat.com Signed-off-by: Thomas Gleixner --- kernel/kthread.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index 01d27164e5b7..956495f0efaf 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); -- 2.20.1