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/...

[John Baldwin]

On Wednesday, October 24, 2012 10:34:34 am Attilio Rao wrote:
> On Wed, Oct 24, 2012 at 3:05 PM, John Baldwin <jhb at freebsd.org> wrote:
> > On Tuesday, October 23, 2012 7:20:04 pm Andre Oppermann wrote:
> >> On 24.10.2012 00:15, mdf at FreeBSD.org wrote:
> >> > On Tue, Oct 23, 2012 at 7:41 AM, Andre Oppermann <andre at 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