per-cpu data...

per-cpu data...

[Rusty Russell]

IIUC, __per_cpu_data is insufficient for Alpha as stands, to use
thread-specific gcc tricks (__thread prepended to the decl, even
though they had a perfectly good __attribute__ extension already).

So, I guess we're stuck with something like:

DECLARE_PER_CPU(int x);

If we're going to do this, we can also mangle the name as well to
avoid accidental "direct" accesses:

eg:
	#define DECLARE_PER_CPU(var) 
		var##__percpu __attribute__((section(".percpu")))

	/* If not SMP: */
	#define per_cpu(var) var##__percpu

(From my reading, ## on "int x" and "__per_cpu" is well-defined).

Thoughts?
Rusty.
--
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.

Re: per-cpu data...

[Richard Henderson]

On Fri, Jul 12, 2002 at 04:01:52PM +1000, Rusty Russell wrote:
> (__thread prepended to the decl, even
> though they had a perfectly good __attribute__ extension already).

Sorry, not our extension.  I just copied it.

> (From my reading, ## on "int x" and "__per_cpu" is well-defined).

Yep.

> Thoughts?

Seems ok, though you really ought to differentiate between
DECLARE and DEFINE.  Otherwise I can see getting screwed again.


r~

Re: per-cpu data...

[Jamie Lokier]

Rusty Russell wrote:
> (From my reading, ## on "int x" and "__per_cpu" is well-defined).

  DECLARE_PER_CPU (int x[3]);

doesn't work, although you can always do

  typedef int three_ints_t[3];
  DECLARE_PER_CPU (three_ints_t x);

I encountered the same thing while doing a user-space
`MAKE_THREAD_SPECIFIC' macro.  The solution I went for looks like this:

  #define DECLARE_PER_CPU(type, name) \
    __attribute__ ((__section (".percpu"))) __typeof__ (type) name##__per_cpu

enjoy,
-- Jamie

Re: per-cpu data...

[Rusty Russell]

In message <20020724133128.A7192@kushida.apsleyroad.org> you write:
> Rusty Russell wrote:
> > (From my reading, ## on "int x" and "__per_cpu" is well-defined).
> 
>   DECLARE_PER_CPU (int x[3]);
> 
> doesn't work, although you can always do
> 
>   typedef int three_ints_t[3];
>   DECLARE_PER_CPU (three_ints_t x);
> 
> I encountered the same thing while doing a user-space
> `MAKE_THREAD_SPECIFIC' macro.  The solution I went for looks like this:
> 
>   #define DECLARE_PER_CPU(type, name) \
>     __attribute__ ((__section (".percpu"))) __typeof__ (type) name##__per_cpu

Hmmm.... Yeah, might as well go the whole way.

Thanks!
Rusty.
--
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.