kthread: Add kthread_start()
In the current API, there is a small time window that kthread_stop()
will skip the ->threadfn() and return -EINTR even if wake_up_process()
is called previously:
CPU 0 CPU 1
===== =====
t = kthread_create(...);
<in the new thread t>
kthread():
...
complete(done);
schedule_preempt_disabled();
wake_up_process(t);
preempt_enabled();
kthread_stop(t);
...
set_bit(KTHREAD_SHOULD_STOP, ...):
...
ret = -EINTR;
if (!test_bit(KTHREAD_SHOULD_STOP, ..)) {
...
} // <- if is false, skip the threadfn()
kthread_exit(ret);
In other words, kthread API doesn't guarantee the threadfn() will be
executed even after wake_up_process(), users have to provide their own
synchronization to verify it.
TODO
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
2 files changed
