Date: Wed, 24 Oct 2012 10:45:39 -0400 From: John Baldwin <jhb@freebsd.org> To: attilio@freebsd.org Cc: mdf@freebsd.org, src-committers@freebsd.org, Andre Oppermann <andre@freebsd.org>, Bruce Evans <brde@optusnet.com.au>, svn-src-user@freebsd.org Subject: Re: svn commit: r241889 - in user/andre/tcp_workqueue/sys: arm/arm cddl/compat/opensolaris/kern cddl/contrib/opensolaris/uts/common/dtrace cddl/contrib/opensolaris/uts/common/fs/zfs ddb dev/acpica dev/... Message-ID: <201210241045.39211.jhb@freebsd.org> In-Reply-To: <CAJ-FndBENEuyaH%2B2Q%2Bigj39tdGmsHh=3arL-Cb2GP3i9WSr_hQ@mail.gmail.com> References: <201210221418.q9MEINkr026751@svn.freebsd.org> <201210241005.38977.jhb@freebsd.org> <CAJ-FndBENEuyaH%2B2Q%2Bigj39tdGmsHh=3arL-Cb2GP3i9WSr_hQ@mail.gmail.com>
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On Wednesday, October 24, 2012 10:34:34 am Attilio Rao wrote:
> On Wed, Oct 24, 2012 at 3:05 PM, John Baldwin <jhb@freebsd.org> wrote:
> > On Tuesday, October 23, 2012 7:20:04 pm Andre Oppermann wrote:
> >> On 24.10.2012 00:15, mdf@FreeBSD.org wrote:
> >> > On Tue, Oct 23, 2012 at 7:41 AM, Andre Oppermann <andre@freebsd.org>
wrote:
> >> >> Struct mtx and MTX_SYSINIT always occur as pair next to each other.
> >> >
> >> > That doesn't matter. Language basics like variable definitions should
> >> > not be obscured by macros. It either takes longer to figure out what
> >> > a variable is (because one needs to look up the definition of the
> >> > macro) or makes it almost impossible (because now e.g. cscope doesn't
> >> > know this is a variable definition.
> >>
> >> Sigh, cscope doesn't expand macros?
> >>
> >> Is there a way to do the cache line alignment in a sane way without
> >> littering __aligned(CACHE_LINE_SIZE) all over the place?
> >
> > I was hoping to do something with an anonymous union or some such like:
> >
> > union mtx_aligned {
> > struct mtx;
> > char[roundup2(sizeof(struct mtx), CACHE_LINE_SIZE)];
> > }
> >
> > I don't know if there is a useful way to define an 'aligned mutex' type
> > that will transparently map to a 'struct mtx', e.g.:
> >
> > typedef struct mtx __aligned(CACHE_LINE_SIZE) aligned_mtx_t;
>
> Unfortunately that doesn't work as I've verified with alc@ few months ago.
> The __aligned() attribute only works with structures definition, not
> objects declaration.
Are you saying that the typedef doesn't (I expect it doesn't), or that this
doesn't:
struct mtx foo __aligned(CACHE_LINE_SIZE);
--
John Baldwin
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