Oleg Nesterov <[email protected]> writes:
> On 04/11, Eric W. Biederman wrote:
>>
>> @@ -435,8 +436,12 @@ static void __init setup_command_line(char *command_line)
>> static void noinline rest_init(void)
>> __releases(kernel_lock)
>> {
>> + int pid;
>> kernel_thread(init, NULL, CLONE_FS | CLONE_SIGHAND);
>> numa_default_policy();
>> +
>> + pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
>> + kthreadd_task = find_task_by_pid(pid);
>> unlock_kernel();
>
> Just curious. What if kernel/kthread.c declares
>
> static struct task_struct *kthreadd_task = &init_task;
>
> an then kthreadd_setup() does kthreadd_task = current. I assume it is always
> safe to try_to_wake_up(idle_thread), because it always TASK_RUNNING. This
> way we don't need to export kthreadd_task.
I did it this way largely so I could use the export in reparent_to_XXX in
daemonize. This way I don't have races in finding kthreadd. Plus
I didn't think of the trick of using the idle_thread...
>> + spin_lock(&kthread_create_lock);
>> + list_add_tail(&create.list, &kthread_create_list);
>> + wake_up_process(kthreadd_task);
>> + spin_unlock(&kthread_create_lock);
>
> Very minor nit, but we don't need to do wake_up under spin_unlock().
I guess that is true. However it doesn't hurt either. I guess
I was keeping the form that I used with wait queues where it may
have mattered. Either that or I just copied a bad example.
Eric
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