diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2014-02-04 20:36:01 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2014-04-18 11:40:29 +0200 |
| commit | e4f9bfb3feaeaca55cf177dadb7e3313836b10f4 (patch) | |
| tree | 14a1a121064fbc30e13176a792f62f8898178081 /arch/ia64/include/uapi | |
| parent | 81cef0fe19e086ff6abfd45e92246f68ffa0185f (diff) | |
ia64: Fix up smp_mb__{before,after}_clear_bit()
IA64 doesn't actually have acquire/release barriers, its a lie!
Add a comment explaining this and fix up the bitop barriers.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/n/tip-akevfh136um9dqvb1ohm55ca@git.kernel.org
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-ia64@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/ia64/include/uapi')
| -rw-r--r-- | arch/ia64/include/uapi/asm/cmpxchg.h | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/ia64/include/uapi/asm/cmpxchg.h b/arch/ia64/include/uapi/asm/cmpxchg.h index 4f37dbbb864..f35109b1d90 100644 --- a/arch/ia64/include/uapi/asm/cmpxchg.h +++ b/arch/ia64/include/uapi/asm/cmpxchg.h @@ -118,6 +118,15 @@ extern long ia64_cmpxchg_called_with_bad_pointer(void); #define cmpxchg_rel(ptr, o, n) \ ia64_cmpxchg(rel, (ptr), (o), (n), sizeof(*(ptr))) +/* + * Worse still - early processor implementations actually just ignored + * the acquire/release and did a full fence all the time. Unfortunately + * this meant a lot of badly written code that used .acq when they really + * wanted .rel became legacy out in the wild - so when we made a cpu + * that strictly did the .acq or .rel ... all that code started breaking - so + * we had to back-pedal and keep the "legacy" behavior of a full fence :-( + */ + /* for compatibility with other platforms: */ #define cmpxchg(ptr, o, n) cmpxchg_acq((ptr), (o), (n)) #define cmpxchg64(ptr, o, n) cmpxchg_acq((ptr), (o), (n)) |