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 | |
| 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')
| -rw-r--r-- | arch/ia64/include/asm/bitops.h | 7 | ||||
| -rw-r--r-- | arch/ia64/include/uapi/asm/cmpxchg.h | 9 |
2 files changed, 11 insertions, 5 deletions
diff --git a/arch/ia64/include/asm/bitops.h b/arch/ia64/include/asm/bitops.h index c27eccd33349..feb8117ed06a 100644 --- a/arch/ia64/include/asm/bitops.h +++ b/arch/ia64/include/asm/bitops.h @@ -65,11 +65,8 @@ __set_bit (int nr, volatile void *addr) *((__u32 *) addr + (nr >> 5)) |= (1 << (nr & 31)); } -/* - * clear_bit() has "acquire" semantics. - */ -#define smp_mb__before_clear_bit() smp_mb() -#define smp_mb__after_clear_bit() do { /* skip */; } while (0) +#define smp_mb__before_clear_bit() barrier(); +#define smp_mb__after_clear_bit() barrier(); /** * clear_bit - Clears a bit in memory diff --git a/arch/ia64/include/uapi/asm/cmpxchg.h b/arch/ia64/include/uapi/asm/cmpxchg.h index 4f37dbbb8640..f35109b1d907 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)) |