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| author | Will Deacon <will.deacon@arm.com> | 2013-09-19 19:06:46 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-09-20 11:04:28 -0500 |
| commit | 8f4c344696b9f9f8471d7f342076ef10ed7f66a5 (patch) | |
| tree | 5266f6e86c81f6694f75e77c84c64a55123b04b1 | |
| parent | dcb30e659287a6b40dafed1362532da42ec27229 (diff) | |
| download | lwn-8f4c344696b9f9f8471d7f342076ef10ed7f66a5.tar.gz lwn-8f4c344696b9f9f8471d7f342076ef10ed7f66a5.zip | |
lockref: use cmpxchg64 explicitly for lockless updates
The cmpxchg() function tends not to support 64-bit arguments on 32-bit
architectures. This could be either due to use of unsigned long
arguments (like on ARM) or lack of instruction support (cmpxchgq on
x86). However, these architectures may implement a specific cmpxchg64()
function to provide 64-bit cmpxchg support instead.
Since the lockref code requires a 64-bit cmpxchg and relies on the
architecture selecting ARCH_USE_CMPXCHG_LOCKREF, move to using cmpxchg64
instead of cmpxchg and allow 32-bit architectures to make use of the
lockless lockref implementation.
Cc: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | lib/lockref.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/lib/lockref.c b/lib/lockref.c index e2cd2c0a8821..677d036cf3c7 100644 --- a/lib/lockref.c +++ b/lib/lockref.c @@ -14,8 +14,8 @@ while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) { \ struct lockref new = old, prev = old; \ CODE \ - old.lock_count = cmpxchg(&lockref->lock_count, \ - old.lock_count, new.lock_count); \ + old.lock_count = cmpxchg64(&lockref->lock_count, \ + old.lock_count, new.lock_count); \ if (likely(old.lock_count == prev.lock_count)) { \ SUCCESS; \ } \ |