Memory transaction instructions

[David Howells]

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

> And for the kernel, where we don't have bad locking, and where we
> actually use fine-grained locks that are _near_ the data that we are
> locking (the lockref of the dcache is obviously one example of that,
> but the skbuff queue you mention is almost certainly exactly the same
> situation): the lock is right by the data that the lock protects, and
> the "shared lock cacheline" model simply does not work. You'll bounce
> the data, and most likely you'll also touch the same lock cacheline
> too.

Yeah.  The reason I was actually wondering about them was if it would be
possible to avoid the requirement to disable interrupts/softirqs to, say,
modify the skbuff queue.  On some arches actually disabling irqs is quite a
heavy operation (I think this is/was true on ppc64, for example; it certainly
was on frv) and it was necessary to "emulate" the disablement.

David