Re: [GIT RFC] percpu: use dynamic percpu allocator as the defaultpercpu allocator

[Martin Schwidefsky]

On Wed, 25 Mar 2009 21:27:49 +0900
Tejun Heo <tj@xxxxxxxxxx> wrote:

> Ingo Molnar wrote:
> > * Tejun Heo <tj@xxxxxxxxxx> wrote:
> > 
> >>> With your patches and a RELOC_HIDE version that uses the GOTENT 
> >>> indirection the kernel won't compile because the "X" constraint 
> >>> for the GOTENT access needs a symbol and there are quite a few 
> >>> users that pass a pointer. I do not see a simple solution for 
> >>> that problem yet.
> >> Ah... okay.  Now I get it.  It wasn't expecting variables there.  How
> >> about doing the following?
> >>
> >>  #define SHIFT_PERCPU_PTR(ptr, offset) (({				\
> >> 	 if (__builtin_constant_p(ptr))					\
> >> 		 do GOTENT trick;					\
> >> 	 else								\
> >> 		 RELOC_HIDE();						\
> >>  }))
> >>
> >> Thanks.
> > 
> > Btw., is there any intermediate fix/workaround i could apply 
> > perhaps? I'd like to send the percpu bits early in the merge window 
> > and would hate to break Martin's arch ...
> 
> Martin's original patch should do the trick although it would be
> slower for static symbols.  I'll merge it and post the tree.

No, my original patch doesn't work. It will break modules that use
static per-cpu variables.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/