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SubjectRe: keventd_create_kthread
In message <> you write:
> wait_task_inactive() will return due to the preemption?
> perhaps wait_task_inactive() should wait until the target task leaves state

That's not enough: it can set that and then get preemted. It really
want to return when the task is off the runqueue. The original
wait_task_inactive() does an incredible complicated and AFAICT useless
dance wrt not locking and disabling preempt explicitly. Ingo, how's
this replacement? (And who wrote this code?)

* wait_task_inactive - wait for a thread to unschedule.
* The caller must ensure that the task *will* unschedule sometime soon,
* else this function might spin for a *long* time. This function can't
* be called with interrupts off, or it may introduce deadlock with
* smp_call_function() if an IPI is sent by the same process we are
* waiting to become inactive.
void wait_task_inactive(task_t * p)
unsigned long flags;
runqueue_t *rq;

rq = task_rq_lock(p, &flags);
/* Must be off runqueue entirely, not preempted. */
if (unlikely(p->array)) {
task_rq_unlock(rq, &flags);
/* If it's preempted: yield. It could be a while. */
if (!task_running(p))
goto repeat;
task_rq_unlock(rq, &flags);

Untested BTW.

Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
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