2 files changed, 31 insertions, 31 deletions

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 84bbadd4d021..4ebaf8519abf 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -76,6 +76,7 @@ static int kthread(void *_create)
 
         /* OK, tell user we're spawned, wait for stop or wakeup */
         __set_current_state(TASK_UNINTERRUPTIBLE);
+        create->result = current;
         complete(&create->started);
         schedule();
 
@@ -96,22 +97,10 @@ static void create_kthread(struct kthread_create_info *create)
 
         /* We want our own signal handler (we take no signals by default). */
         pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
-        if (pid < 0) {
+        if (pid < 0)
                 create->result = ERR_PTR(pid);
-        } else {
-                struct sched_param param = { .sched_priority = 0 };
+        else
                 wait_for_completion(&create->started);
-                read_lock(&tasklist_lock);
-                create->result = find_task_by_pid_ns(pid, &init_pid_ns);
-                read_unlock(&tasklist_lock);
-                /*
-                 * root may have changed our (kthreadd's) priority or CPU mask.
-                 * The kernel thread should not inherit these properties.
-                 */
-                sched_setscheduler(create->result, SCHED_NORMAL, &param);
-                set_user_nice(create->result, KTHREAD_NICE_LEVEL);
-                set_cpus_allowed_ptr(create->result, cpu_all_mask);
-        }
         complete(&create->done);
 }
 
@@ -154,11 +143,20 @@ struct task_struct *kthread_create(int (*threadfn)(void *data),
         wait_for_completion(&create.done);
 
         if (!IS_ERR(create.result)) {
+                struct sched_param param = { .sched_priority = 0 };
                 va_list args;
+
                 va_start(args, namefmt);
                 vsnprintf(create.result->comm, sizeof(create.result->comm),
                           namefmt, args);
                 va_end(args);
+                /*
+                 * root may have changed our (kthreadd's) priority or CPU mask.
+                 * The kernel thread should not inherit these properties.
+                 */
+                sched_setscheduler_nocheck(create.result, SCHED_NORMAL, &param);
+                set_user_nice(create.result, KTHREAD_NICE_LEVEL);
+                set_cpus_allowed_ptr(create.result, cpu_all_mask);
         }
         return create.result;
 }
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index b6b966ce1451..f71fb2a08950 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -966,20 +966,20 @@ undo:
 }
 
 #ifdef CONFIG_SMP
-static struct workqueue_struct *work_on_cpu_wq __read_mostly;
 
 struct work_for_cpu {
-        struct work_struct work;
+        struct completion completion;
         long (*fn)(void *);
         void *arg;
         long ret;
 };
 
-static void do_work_for_cpu(struct work_struct *w)
+static int do_work_for_cpu(void *_wfc)
 {
-        struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work);
-
+        struct work_for_cpu *wfc = _wfc;
         wfc->ret = wfc->fn(wfc->arg);
+        complete(&wfc->completion);
+        return 0;
 }
 
 /**
@@ -990,17 +990,23 @@ static void do_work_for_cpu(struct work_struct *w)
  *
  * This will return the value @fn returns.
  * It is up to the caller to ensure that the cpu doesn't go offline.
+ * The caller must not hold any locks which would prevent @fn from completing.
  */
 long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
 {
-        struct work_for_cpu wfc;
-
-        INIT_WORK(&wfc.work, do_work_for_cpu);
-        wfc.fn = fn;
-        wfc.arg = arg;
-        queue_work_on(cpu, work_on_cpu_wq, &wfc.work);
-        flush_work(&wfc.work);
-
+        struct task_struct *sub_thread;
+        struct work_for_cpu wfc = {
+                .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
+                .fn = fn,
+                .arg = arg,
+        };
+
+        sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
+        if (IS_ERR(sub_thread))
+                return PTR_ERR(sub_thread);
+        kthread_bind(sub_thread, cpu);
+        wake_up_process(sub_thread);
+        wait_for_completion(&wfc.completion);
         return wfc.ret;
 }
 EXPORT_SYMBOL_GPL(work_on_cpu);
@@ -1016,8 +1022,4 @@ void __init init_workqueues(void)
         hotcpu_notifier(workqueue_cpu_callback, 0);
         keventd_wq = create_workqueue("events");
         BUG_ON(!keventd_wq);
-#ifdef CONFIG_SMP
-        work_on_cpu_wq = create_workqueue("work_on_cpu");
-        BUG_ON(!work_on_cpu_wq);
-#endif
 }