Re: Why is wmb() a no-op on x86_64?

["Bryan O'Sullivan" <bos@pathscale.com>]

On Wed, 2006-01-18 at 12:06 -0500, Jes Sorensen wrote:

> A job for mmiowb() perhaps?

That might be suitable.  It's a no-op on most platforms, but it's only
used by a handful of drivers:

        drivers/scsi/qla1280.c
        drivers/sn/ioc4.c
        drivers/net/bnx2.c
        drivers/net/sky2.c
        drivers/net/s2io.c
        drivers/net/tg3.c

If the semantics were to change so that it really did a write barrier, I
doubt any existing users would notice.  In fact, based on the comments
in some drivers, at least some authors think it does already, when it
typically doesn't.

	<b

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/