Re: [PATCH] Document Linux's memory barriers

Alan Cox
2006-03-08T00:33:32Z

On Maw, 2006-03-07 at 20:09 +0000, David Howells wrote:
> Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>
> > Better meaningful example would be barriers versus an IRQ handler. Which
> > leads nicely onto section 2
>
> Yes, except that I can't think of one that's feasible that doesn't have to do
> with I/O - which isn't a problem if you are using the proper accessor
> functions.

We get them off bus masters for one and you can construct silly versions
of the other.

There are several kernel instances of

while(*ptr != HAVE_RESPONDED && time_before(jiffies, timeout))
rmb();

where we wait for hardware to bus master respond when it is fast and
doesn't IRQ.