diff options
| author | marcel <marcel@FreeBSD.org> | 2002-11-16 17:05:06 +0000 |
|---|---|---|
| committer | marcel <marcel@FreeBSD.org> | 2002-11-16 17:05:06 +0000 |
| commit | 448c522a41592e4428f041449236ea9cae62da5e (patch) | |
| tree | b6338e19ceea921cd4469d68ea0cd64b12298d6b /lib/libc_r | |
| parent | 0f47f00a644da2af9b6cd625bb5b1c38a77a1463 (diff) | |
| download | FreeBSD-src-448c522a41592e4428f041449236ea9cae62da5e.zip FreeBSD-src-448c522a41592e4428f041449236ea9cae62da5e.tar.gz | |
Implement the lock with a cmpxchg instruction instead of a xchg.
Both are atomic, but the cmpxchg has memory ordering hints. We
give this acquire semantics.
NOTE: The unlock in libc_r is implemented by a "normal" assign
statement. This is not correct on ia64 due to the memory ordering
characteristics of the architecture. We need release semantics
for an unlock.
Diffstat (limited to 'lib/libc_r')
| -rw-r--r-- | lib/libc_r/arch/ia64/_atomic_lock.S | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/lib/libc_r/arch/ia64/_atomic_lock.S b/lib/libc_r/arch/ia64/_atomic_lock.S index 836b375..d2fc18a 100644 --- a/lib/libc_r/arch/ia64/_atomic_lock.S +++ b/lib/libc_r/arch/ia64/_atomic_lock.S @@ -38,11 +38,12 @@ * is not currently locked. * * long _atomic_lock(long *); - * eax will contain the return value (zero if lock obtained). */ ENTRY(_atomic_lock, 1) + mov ar.ccv = r0 add r14 = 1, r0 + nop 0 ;; - xchg8 r8 = [r32], r14 + cmpxchg8.acq r8 = [r32], r14, ar.ccv br.ret.sptk rp END(_atomic_lock) |
