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SubjectRe: [PATCH 08/13] hrtimer: remove data field

* Roman Zippel <zippel@linux-m68k.org> wrote:

> On Mon, 13 Feb 2006, Ingo Molnar wrote:
>
> > > The nanosleep cleanup allows to remove the data field of hrtimer. The
> > > callback function can use container_of() to get it's own data. Since
> > > the hrtimer structure is usually embedded in other structures, the
> > > code also becomes a bit simpler.
> >
> > i addressed this when you first raised this issue (back in the ktimers
> > flamewars), and generally the feeling of people i asked was that doing
> > the container_of() approach is less readable than an explicit 'data'
> > field. It also deviates from struct timer_list, which we wanted to stay
> > close to. Furthermore, for standalone hrtimers this creates the need to
> > generate a wrapper structure. So i dont really like this change - but no
> > strong feelings either way.
>
> With the complete size reduction struct hrtimer becomes 32 bytes on 32
> bits archs and so we can fit the basic hrtimer into one or two cache
> lines. container_of() is becoming more and more common in the kernel,
> so I don't know who asked, it's not that difficult to use. I agree it
> makes simple test modules a bit more difficult, but so far the more
> common case is that this structure is embedded in other structures and
> container_of() creates simpler code. Additionally you get type
> checking for free, which you don't get with a void pointer.

yeah, i agreed with you back then too. (in fact i raised doing the same
for timer_list, which is embedded in other structs quite frequently too,
but this thought didnt acquire much traction either.)

But clearly this is not a must-have item for 2.6.16.

Ingo
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