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/...

[Attilio Rao]

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.

Attilio


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