diff options
Diffstat (limited to 'lib/libpthread/arch/sparc')
| -rw-r--r-- | lib/libpthread/arch/sparc/_atomic_lock.c | 31 |
1 files changed, 28 insertions, 3 deletions
diff --git a/lib/libpthread/arch/sparc/_atomic_lock.c b/lib/libpthread/arch/sparc/_atomic_lock.c index 6415e25c912..c46a0ce6da8 100644 --- a/lib/libpthread/arch/sparc/_atomic_lock.c +++ b/lib/libpthread/arch/sparc/_atomic_lock.c @@ -1,4 +1,4 @@ -/* $OpenBSD: _atomic_lock.c,v 1.4 1998/12/21 13:03:45 d Exp $ */ +/* $OpenBSD: _atomic_lock.c,v 1.5 1999/02/07 23:51:00 d Exp $ */ /* * Atomic lock for sparc */ @@ -8,12 +8,37 @@ int _atomic_lock(volatile _spinlock_lock_t * lock) { - return _thread_slow_atomic_lock(lock); + _spinlock_lock_t old; + + /* + * " ldstub [address], reg_rd + * + * The atomic load-store instructions copy a byte from memory + * into r[rd]m then rewrite the addressed byte in memory to all + * ones [_SPINLOCK_LOCKED]. The operation is performed + * atomically, that is, without allowing intervening interrupts + * or deferred traps. In a multiprocessor system, two or more + * processors executing atomic load-store unsigned byte [...] + * addressing the same byte [...] simultaneously are guaranteed + * to execute them in an undefined, but serial order." + * - p101, The SPARC Architecure Manual (version 8) Prentice-Hall + * + * "LDSTUB loads a byte value from memory to a register and writes + * the value FF_16 into the addressed byte atomically. LDSTUB + * is the classic test-and-set instruction. Like SWAP, it has + * a consensus number of two and so cannot resolve more than + * two contending processes in a wait-free fashion." + * - p129, The SPARC Architecture Manual (version 9) Prentice-Hall + * (See also section J.6 (spinlocks)) + */ + __asm__("ldstub %1,%0" : "=r" (old), "+m" (*lock)); + + return (old == _SPINLOCK_LOCKED); } int _atomic_is_locked(volatile _spinlock_lock_t * lock) { - return _thread_slow_atomic_is_locked(lock); + return (*lock == _SPINLOCK_LOCKED); } |