btw.,
(a bit more of 'nit-picking' :-)
to work properly, kthread_stop() should also impose one of the
following requirements on a 'kthread' loop:
- a loop can be interrupted _only_ as a result of
'kthread_should_stop() == true'
and no concurrent kthread_stop() calls are possible;
or
- if it can exit due to another reason, a user has to use additional
synchronization means to make sure than kthread_stop() is never
called/running after a main loop has finished (makes sense as 'struct
task_struct *' can be 'obsolete')
otherwise,
note, the comment in kthread() that says "It might have exited on its
own, w/o kthread_stop. Check."
so let's suppose a 'kthread' is really "exiting on its own" and at the
same time, kthread_stop() is running on another CPU... as a result, we
may end up with kthread_stop() being blocked on
wait_for_completion(&kthread_stop_info.done) without anybody to call
complete().
Although, the requirements above don't seem to be so insane in this case.
static int kthread(void *_create)
{
...
if (!kthread_should_stop())
ret = threadfn(data); <---- our main loop is
inside this function
/* It might have exited on its own, w/o kthread_stop. Check. */
if (kthread_should_stop()) {
kthread_stop_info.err = ret;
complete(&kthread_stop_info.done);
}
return 0;
}
--
Best regards,
Dmitry Adamushko
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