1 files changed, 237 insertions, 0 deletions
diff --git a/arch/s390/include/asm/rwsem.h b/arch/s390/include/asm/rwsem.h
new file mode 100644
index 000000000..4b43ee7e6
--- /dev/null
+++ b/arch/s390/include/asm/rwsem.h
@@ -0,0 +1,237 @@
+#ifndef _S390_RWSEM_H
+#define _S390_RWSEM_H
+
+/*
+ *  S390 version
+ *    Copyright IBM Corp. 2002
+ *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
+ *
+ *  Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
+ */
+
+/*
+ *
+ * The MSW of the count is the negated number of active writers and waiting
+ * lockers, and the LSW is the total number of active locks
+ *
+ * The lock count is initialized to 0 (no active and no waiting lockers).
+ *
+ * When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case of an
+ * uncontended lock. This can be determined because XADD returns the old value.
+ * Readers increment by 1 and see a positive value when uncontended, negative
+ * if there are writers (and maybe) readers waiting (in which case it goes to
+ * sleep).
+ *
+ * The value of WAITING_BIAS supports up to 32766 waiting processes. This can
+ * be extended to 65534 by manually checking the whole MSW rather than relying
+ * on the S flag.
+ *
+ * The value of ACTIVE_BIAS supports up to 65535 active processes.
+ *
+ * This should be totally fair - if anything is waiting, a process that wants a
+ * lock will go to the back of the queue. When the currently active lock is
+ * released, if there's a writer at the front of the queue, then that and only
+ * that will be woken up; if there's a bunch of consequtive readers at the
+ * front, then they'll all be woken up, but no other readers will be.
+ */
+
+#ifndef _LINUX_RWSEM_H
+#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
+#endif
+
+#define RWSEM_UNLOCKED_VALUE	0x0000000000000000L
+#define RWSEM_ACTIVE_BIAS	0x0000000000000001L
+#define RWSEM_ACTIVE_MASK	0x00000000ffffffffL
+#define RWSEM_WAITING_BIAS	(-0x0000000100000000L)
+#define RWSEM_ACTIVE_READ_BIAS	RWSEM_ACTIVE_BIAS
+#define RWSEM_ACTIVE_WRITE_BIAS	(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+
+/*
+ * lock for reading
+ */
+static inline void __down_read(struct rw_semaphore *sem)
+{
+	signed long old, new;
+
+	asm volatile(
+		"	lg	%0,%2\n"
+		"0:	lgr	%1,%0\n"
+		"	aghi	%1,%4\n"
+		"	csg	%0,%1,%2\n"
+		"	jl	0b"
+		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
+		: "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)
+		: "cc", "memory");
+	if (old < 0)
+		rwsem_down_read_failed(sem);
+}
+
+/*
+ * trylock for reading -- returns 1 if successful, 0 if contention
+ */
+static inline int __down_read_trylock(struct rw_semaphore *sem)
+{
+	signed long old, new;
+
+	asm volatile(
+		"	lg	%0,%2\n"
+		"0:	ltgr	%1,%0\n"
+		"	jm	1f\n"
+		"	aghi	%1,%4\n"
+		"	csg	%0,%1,%2\n"
+		"	jl	0b\n"
+		"1:"
+		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
+		: "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)
+		: "cc", "memory");
+	return old >= 0 ? 1 : 0;
+}
+
+/*
+ * lock for writing
+ */
+static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
+{
+	signed long old, new, tmp;
+
+	tmp = RWSEM_ACTIVE_WRITE_BIAS;
+	asm volatile(
+		"	lg	%0,%2\n"
+		"0:	lgr	%1,%0\n"
+		"	ag	%1,%4\n"
+		"	csg	%0,%1,%2\n"
+		"	jl	0b"
+		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
+		: "Q" (sem->count), "m" (tmp)
+		: "cc", "memory");
+	if (old != 0)
+		rwsem_down_write_failed(sem);
+}
+
+static inline void __down_write(struct rw_semaphore *sem)
+{
+	__down_write_nested(sem, 0);
+}
+
+/*
+ * trylock for writing -- returns 1 if successful, 0 if contention
+ */
+static inline int __down_write_trylock(struct rw_semaphore *sem)
+{
+	signed long old;
+
+	asm volatile(
+		"	lg	%0,%1\n"
+		"0:	ltgr	%0,%0\n"
+		"	jnz	1f\n"
+		"	csg	%0,%3,%1\n"
+		"	jl	0b\n"
+		"1:"
+		: "=&d" (old), "=Q" (sem->count)
+		: "Q" (sem->count), "d" (RWSEM_ACTIVE_WRITE_BIAS)
+		: "cc", "memory");
+	return (old == RWSEM_UNLOCKED_VALUE) ? 1 : 0;
+}
+
+/*
+ * unlock after reading
+ */
+static inline void __up_read(struct rw_semaphore *sem)
+{
+	signed long old, new;
+
+	asm volatile(
+		"	lg	%0,%2\n"
+		"0:	lgr	%1,%0\n"
+		"	aghi	%1,%4\n"
+		"	csg	%0,%1,%2\n"
+		"	jl	0b"
+		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
+		: "Q" (sem->count), "i" (-RWSEM_ACTIVE_READ_BIAS)
+		: "cc", "memory");
+	if (new < 0)
+		if ((new & RWSEM_ACTIVE_MASK) == 0)
+			rwsem_wake(sem);
+}
+
+/*
+ * unlock after writing
+ */
+static inline void __up_write(struct rw_semaphore *sem)
+{
+	signed long old, new, tmp;
+
+	tmp = -RWSEM_ACTIVE_WRITE_BIAS;
+	asm volatile(
+		"	lg	%0,%2\n"
+		"0:	lgr	%1,%0\n"
+		"	ag	%1,%4\n"
+		"	csg	%0,%1,%2\n"
+		"	jl	0b"
+		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
+		: "Q" (sem->count), "m" (tmp)
+		: "cc", "memory");
+	if (new < 0)
+		if ((new & RWSEM_ACTIVE_MASK) == 0)
+			rwsem_wake(sem);
+}
+
+/*
+ * downgrade write lock to read lock
+ */
+static inline void __downgrade_write(struct rw_semaphore *sem)
+{
+	signed long old, new, tmp;
+
+	tmp = -RWSEM_WAITING_BIAS;
+	asm volatile(
+		"	lg	%0,%2\n"
+		"0:	lgr	%1,%0\n"
+		"	ag	%1,%4\n"
+		"	csg	%0,%1,%2\n"
+		"	jl	0b"
+		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
+		: "Q" (sem->count), "m" (tmp)
+		: "cc", "memory");
+	if (new > 1)
+		rwsem_downgrade_wake(sem);
+}
+
+/*
+ * implement atomic add functionality
+ */
+static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
+{
+	signed long old, new;
+
+	asm volatile(
+		"	lg	%0,%2\n"
+		"0:	lgr	%1,%0\n"
+		"	agr	%1,%4\n"
+		"	csg	%0,%1,%2\n"
+		"	jl	0b"
+		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
+		: "Q" (sem->count), "d" (delta)
+		: "cc", "memory");
+}
+
+/*
+ * implement exchange and add functionality
+ */
+static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
+{
+	signed long old, new;
+
+	asm volatile(
+		"	lg	%0,%2\n"
+		"0:	lgr	%1,%0\n"
+		"	agr	%1,%4\n"
+		"	csg	%0,%1,%2\n"
+		"	jl	0b"
+		: "=&d" (old), "=&d" (new), "=Q" (sem->count)
+		: "Q" (sem->count), "d" (delta)
+		: "cc", "memory");
+	return new;
+}
+
+#endif /* _S390_RWSEM_H */