Re: [PATCH] It may not be assumed that wake_up(), finish_wait() and co. imply a memory barrier

Ingo Molnar
2009-04-23T21:25:16Z

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Thu, 23 Apr 2009, David Howells wrote:
> >
> > Well, Ingo's point is it could be left up to the caller of
> > wake_up() to supply the barrier:

Well, i mainly reacted to your documentation patch which was
incorrect as it said wake-up implies a _FULL_ memory barrier.

I also suggested that lockless code should have its barriers clearly
documented and they should not really rely on kernel facilities
acting as memory barriers.

Then i also suggested that maybe in the future we could remove the
smp_wmb() from try_to_wake_up(). That was just an afterthought, and
a rather stupid one at that, as Linus quickly noted :-)

Ingo