On Mon, Oct 19, 2015 at 12:11 PM, Arnd Bergmann arnd@arndb.de wrote:
On Monday 19 October 2015 09:34:15 Geert Uytterhoeven wrote:
On Wed, Oct 7, 2015 at 1:23 PM, Arnd Bergmann arnd@arndb.de wrote:
static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
which truncates the result to 32 bit.
Woops.
See also my unanswered question in "atomic64 on 32-bit vs 64-bit (was: Re: Add virtio gpu driver.)", which is still valid: https://lkml.org/lkml/2015/6/28/18
Regarding your question of
Instead of sprinkling casts, is there any good reason why atomic64_read() and atomic64_t aren't "long long" everywhere, cfr. u64?
I assume the answer is that some (all?) 64-bit architectures intentionally return 'long' here, in order for atomic_long_read() to return 'long' on all architectures, given the definitions from include/asm-generic/atomic-long.h
We would have to either change those, or we have to pick between atomic_long_* or atomic64_* to have a consistent return type.
I guess the main reason is this comment in include/asm-generic/atomic-long.h, which I hadn't noticed before:
* Casts for parameters are avoided for existing atomic functions in order to * avoid issues with cast-as-lval under gcc 4.x and other limitations that the * macros of a platform may have.
Still, it's a pity, as printing atomic_64 is one more place where casts are needed in callers.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds