21 May
2015
21 May
'15
8:56 a.m.
Hi Arnd,
On Wed, May 20, 2015 at 5:07 PM, Arnd Bergmann arnd@arndb.de wrote:
--- a/include/uapi/asm-generic/sembuf.h +++ b/include/uapi/asm-generic/sembuf.h @@ -12,23 +12,29 @@
- everyone just ended up making identical copies without specific
- optimizations, so we may just as well all use the same one.
- 64 bit architectures typically define a 64 bit __kernel_time_t,
- 64 bit architectures use a 64-bit __kernel_time_t here, while
- 32 bit architectures have a pair of unsigned long values.
- so they do not need the first two padding words.
- On big-endian systems, the padding is in the wrong place.
- Pad space is left for:
- 64-bit time_t to solve y2038 problem
- 2 miscellaneous 32-bit values
- On big-endian systems, the padding is in the wrong place for
- historic reasons, so user space has to reconstruct a time_t
- value using
- user_semid_ds.sem_otime = kernel_semid64_ds.sem_otime +
(long long)(kernel_semid64_ds.sem_otime_high << 32)
The cast to "long long" should be inside the parentheses, to promote the (32-bit) sem_otime_high to a first 64-bit integer first. Else it will be shifted into oblivion (oh no, C undefined behavior).
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