Messages in this thread | | | Date | Thu, 19 Feb 2004 02:10:18 -0800 | From | Andrew Morton <> | Subject | Re: keventd_create_kthread |
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Srivatsa Vaddagiri <vatsa@in.ibm.com> wrote: > > On Thu, Feb 19, 2004 at 08:12:19AM +0000, Andrew Morton wrote: > > However, if that wake_up_process() comes too early we'll just flip the new > > thread out of TASK_INTERUPTIBLE into TASK_RUNNING and the schedule() in > > kthread() will fall straight through. So perhaps we can simply remove the > > wait_task_inactive()? > > If wake_up_process() comes too early (when the target task is still > in TASK_RUNNING state), then won't wake_up_process() be a no-op? > In which case, the target kthread will miss a wake-up event > (kthread_start/kthread_stop)?
No, that's OK - the new kernel thread sets TASK_INTERRUPTIBLE before waking the invoking thread via complete():
new thread:
/* OK, tell user we're spawned, wait for stop or wakeup */ __set_current_state(TASK_INTERRUPTIBLE); complete(&create->started); schedule();
invoker:
wait_for_completion(&create->started); create->result = find_task_by_pid(pid); wait_task_inactive(create->result);
It's the window after the complete() and before the schedule() where wait_task_inactive() is spinning.
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