A much better atomic lock routine.

1 files changed, 9 insertions, 43 deletions

diff --git a/lib/libpthread/arch/mips64/_atomic_lock.c b/lib/libpthread/arch/mips64/_atomic_lock.c
index cb5b42a1162..e85335f7466 100644
--- a/lib/libpthread/arch/mips64/_atomic_lock.c
+++ b/lib/libpthread/arch/mips64/_atomic_lock.c
@@ -1,58 +1,24 @@
-/*	$OpenBSD: _atomic_lock.c,v 1.2 2009/02/15 17:48:58 deraadt Exp $	*/
-
-/* Public domain.  Written by David Leonard */
+/*	$OpenBSD: _atomic_lock.c,v 1.3 2009/06/01 23:17:52 miod Exp $	*/
 
 /*
  * Atomic lock for mips
+ * Written by Miodrag Vallat <miod@openbsd.org> - placed in the public domain.
  */
 
-#include "pthread.h"
-#include "pthread_private.h"
 #include "spinlock.h"
-#include <signal.h>
 
-/*
- * uthread atomic lock: 
- * 	attempt to acquire a lock (by giving it a non-zero value).
- *	Return zero on success, or the lock's value on failure
- */
 int
 _atomic_lock(volatile _spinlock_lock_t *lock)
 {
-#if __mips >= 2
 	_spinlock_lock_t old;
-	_spinlock_lock_t temp;
 
-	do {
-		/*
-		 * On a mips2 machine and above, we can use ll/sc.
-		 * Read the lock and tag the cache line with a 'load linked'
-		 * instruction. (Register 17 (LLAddr) will hold the 
-		 * physical address of lock for diagnostic purposes);
-		 * (Under pathologically heavy swapping, the physaddr may 
-		 * change! XXX)
-		 */
-		__asm__("ll %0, %1" : "=r"(old) : "m"(*lock));
-		if (old != _SPINLOCK_UNLOCKED) 
-			break; /* already locked */
-		/*
-		 * Try and store a 1 at the tagged lock address.  If
-		 * anyone else has since written it, the tag on the cache
-		 * line will have been wiped, and temp will be set to zero
-		 * by the 'store conditional' instruction.
-		 */
-		temp = _SPINLOCK_LOCKED;
-		__asm__("sc  %0, %1" : "=r"(temp), "=m"(*lock)
-				     : "0"(temp));
-	} while (temp == 0);
+	__asm__ __volatile__ (
+	"1:	ll	%0,	0(%1)\n"
+	"	sc	%2,	0(%1)\n"
+	"	beqz	%2,	1b\n"
+	"	 nop\n" :
+		"=r"(old) :
+		"r"(lock), "r"(_SPINLOCK_LOCKED) : "memory");
 
 	return (old != _SPINLOCK_UNLOCKED);
-#else
-	/*
-	 * Older MIPS cpus have no way of doing an atomic lock
-	 * without some kind of shift to supervisor mode.
-	 */
-
-	return (_thread_slow_atomic_lock(lock));
-#endif
 }