Re: [PATCH 2/4] swait: add the missing killable swaits

From: Davidlohr Bueso
Date: Fri Jul 07 2017 - 18:28:10 EST

On Fri, 07 Jul 2017, Linus Torvalds wrote:

On Tue, Jul 4, 2017 at 7:06 PM, Davidlohr Bueso <dave@xxxxxxxxxxxx> wrote:

So here's something that boots and builds a kernel. Any thoughts?

This patch ios just nasty crap. Sorry.

It has random whitespace changfes that look entirely unrelated to trhe
actual real meat of the patch, and that actually make whitespace

Ok sorry, fwiw those were 80-line fixlets I thought were trivial enough
to just fly by.


That alone should just mean that this patch needs to be thrown away
and never ever looked at again.

But also, this is fundamentally garbage.

Exactly for the same reasons that the swait interfaces were
fundamentally broken.

It *looks* like it works on regular wait queues, and people can start
using it that way, but it actually doesn't have the right semantics at

The new "lockless" function ONLY works if you don't have a private
wakeup function.

Oh indeed, this was always my intent. Going back to the patch, when
checking DEFINE_WAIT_FUNC I clearly overlooked the ->func()
implications, breaking all kinds of semantics. With that and the
constraints aforementioned in the patch, I see no sane way of using

So no, this is not only NAK'ed, the whole approach is pure and utter
shit and this needs to be buried deep and forgotten about so that it
never ever comes back to life.

Given that you seem to agree that the lockless version is possible as
long as we keep semantics, this imho is another point for some form of
simplified waitqueues.

But yeah.