Merge git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus

* git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus:
  work_on_cpu(): rewrite it to create a kernel thread on demand
  kthread: move sched-realeted initialization from kthreadd context
  kthread: Don't looking for a task in create_kthread() #2

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 84bbadd4d0213c1558ade617ab49695df0b1bd9f..4ebaf8519abf64fb0cc4e93ef42d7ad0cf286c9f 100644 (file)
--- 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 b6b966ce1451adf7c71fffd38524e68587f7504e..f71fb2a089503534eec8d8790f82d9702a3545cc 100644 (file)
--- 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
 }