* Frederic Weisbecker <fweis...@gmail.com> wrote:
> On Tue, Mar 29, 2016 at 03:05:14PM +0200, Ingo Molnar wrote:
> >
> > * Ingo Molnar <mi...@kernel.org> wrote:
> >
> > >
> > > * Linus Torvalds <torva...@linux-foundation.org> wrote:
> > >
> > > > On Tue, Mar 29, 2016 at 4:44 AM, Ingo Molnar <mi...@kernel.org> wrote:
> > > > >
> > > > > Harmonizing thread_info::flags does not look easy, given how much
> > > > > assembly code
> > > > > accesses this field.
> > > >
> > > > It might not be too bad.
> > > >
> > > > For 32-bit architectures (which is still most of them), it's just a
> > > >
> > > > unsigned int/long -> atomic_t
> > > >
> > > > and for 64-bit architectures you end up with three choices:
> > > >
> > > > - it's already 32-bit (alpha, ia64, x86):
> > > >
> > > > unsigned int -> atomic_t
> > > >
> > > > - little-endian long:
> > > >
> > > > atomic_t flags
> > > > unsigned int padding;
> > > >
> > > > - big-endian long (only powerpc? Maybe there's a big-endian MIPS
> > > > still?)
> > > >
> > > > unsigned int padding;
> > > > atomic_t flags;
> > >
> > > Hm, that indeed sounds fairly nice and doable - I thought some
> > > architectures do
> > > have a task flag above bit 31, but that does not appear to be so ...
> > >
> > > Right now we seem to have 27 bits defined in include/linux/sched.h, with
> > > 5 more
> > > bits left for the future. Here's their current usage histogram in the
> > > kernel
> > > source:
> > >
> > > PF_KTHREAD : 68
> > > PF_MEMALLOC : 65
> >
> > Argh, my reading comprehension skills suck today.
> >
> > That's a totally useless analysis of task_struct::flags, while we want to
> > convert
> > thread_info::flags...
>
> Actually we want to convert that one too :-)
> In fact I planned to start there.
Sounds good to me! I also volunteer the x86 architecture to be the guinea pig
to
convert thread_info::flags to atomic_t ;-) [*]
Thanks,
Ingo
