Provide a specific rw_cas() function for MP kernels; stolen from m88k.

ok jsing@, deraadt@

2 files changed, 35 insertions, 2 deletions

diff --git a/sys/arch/hppa/hppa/lock_machdep.c b/sys/arch/hppa/hppa/lock_machdep.c
index 00377d39667..5feebe9616e 100644
--- a/sys/arch/hppa/hppa/lock_machdep.c
+++ b/sys/arch/hppa/hppa/lock_machdep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: lock_machdep.c,v 1.2 2010/05/17 11:25:08 jsing Exp $	*/
+/*	$OpenBSD: lock_machdep.c,v 1.3 2011/01/12 21:11:12 kettenis Exp $	*/
 
 /*
  * Copyright (c) 2007 Artur Grabowski <art@openbsd.org>
@@ -204,3 +204,31 @@ __mp_lock_held(struct __mp_lock *mpl)
 {
 	return mpl->mpl_cpu == curcpu();
 }
+
+/*
+ * Emulate a compare-and-swap instruction for rwlocks, by using a
+ * __cpu_simple_lock as a critical section.
+ *
+ * Since we are only competing against other processors for rwlocks,
+ * it is not necessary in this case to disable interrupts to prevent
+ * reentrancy on the same processor.
+ */
+
+__cpu_simple_lock_t rw_cas_spinlock = __SIMPLELOCK_UNLOCKED;
+
+int
+rw_cas_hppa(volatile unsigned long *p, unsigned long o, unsigned long n)
+{
+	int rc = 0;
+
+	__cpu_simple_lock(&rw_cas_spinlock);
+
+	if (*p != o)
+		rc = 1;
+	else
+		*p = n;
+
+	__cpu_simple_unlock(&rw_cas_spinlock);
+
+	return (rc);
+}
diff --git a/sys/arch/hppa/include/lock.h b/sys/arch/hppa/include/lock.h
index 48430c7163f..5d21e8cb8ea 100644
--- a/sys/arch/hppa/include/lock.h
+++ b/sys/arch/hppa/include/lock.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: lock.h,v 1.3 2011/01/12 21:07:12 kettenis Exp $	*/
+/*	$OpenBSD: lock.h,v 1.4 2011/01/12 21:11:12 kettenis Exp $	*/
 
 /* public domain */
 
@@ -47,4 +47,9 @@ __cpu_simple_unlock(__cpu_simple_lock_t *l)
 	*l = __SIMPLELOCK_UNLOCKED;
 }
 
+#if defined(_KERNEL) && defined(MULTIPROCESSOR)
+int	rw_cas_hppa(volatile unsigned long *, unsigned long, unsigned long);
+#define	rw_cas rw_cas_hppa
+#endif
+
 #endif	/* _HPPA_LOCK_H_ */