Re: [PATCH 12/13] rust: sync: introduce `CondVar`

[Wedson Almeida Filho <wedsonaf@gmail.com>]

On Thu, Mar 30, 2023 at 02:52:23PM +0200, Peter Zijlstra wrote:
> On Thu, Mar 30, 2023 at 01:39:53AM -0300, Wedson Almeida Filho wrote:
> > From: Wedson Almeida Filho <walmeida@microsoft.com>
> > 
> > This is the traditional condition variable or monitor synchronisation
> > primitive. It is implemented with C's `wait_queue_head_t`.
> > 
> > It allows users to release a lock and go to sleep while guaranteeing
> > that notifications won't be missed. This is achieved by enqueuing a wait
> > entry before releasing the lock.
> > 
> 
> > +/// A conditional variable.
> > +///
> > +/// Exposes the kernel's [`struct wait_queue_head`] as a condition variable. It allows the caller to
> > +/// atomically release the given lock and go to sleep. It reacquires the lock when it wakes up. And
> > +/// it wakes up when notified by another thread (via [`CondVar::notify_one`] or
> > +/// [`CondVar::notify_all`]) or because the thread received a signal. It may also wake up
> > +/// spuriously.
> 
> Urgh so wide :-/

Thanks for reviewing :)

> But no, threads can *always* and for any reason, have spurious wakeups.

I don't believe I said otherwise. Is there anything in the text above you'd like to see changed?

> Also, is this hard tied to mutex? If so, you should probably use swait
> instead of wait.

This is not tied to mutex, it works with any lock.

Cheers,
-Wedson