summaryrefslogtreecommitdiff
path: root/arch/s390/include/asm/rwsem.h
diff options
context:
space:
mode:
Diffstat (limited to 'arch/s390/include/asm/rwsem.h')
-rw-r--r--arch/s390/include/asm/rwsem.h387
1 files changed, 387 insertions, 0 deletions
diff --git a/arch/s390/include/asm/rwsem.h b/arch/s390/include/asm/rwsem.h
new file mode 100644
index 000000000000..9d2a17971805
--- /dev/null
+++ b/arch/s390/include/asm/rwsem.h
@@ -0,0 +1,387 @@
+#ifndef _S390_RWSEM_H
+#define _S390_RWSEM_H
+
+/*
+ * include/asm-s390/rwsem.h
+ *
+ * S390 version
+ * Copyright (C) 2002 IBM Deutschland Entwicklung GmbH, IBM Corporation
+ * 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
+
+#ifdef __KERNEL__
+
+#include <linux/list.h>
+#include <linux/spinlock.h>
+
+struct rwsem_waiter;
+
+extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *);
+extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *);
+extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);
+extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *);
+extern struct rw_semaphore *rwsem_downgrade_write(struct rw_semaphore *);
+
+/*
+ * the semaphore definition
+ */
+struct rw_semaphore {
+ signed long count;
+ spinlock_t wait_lock;
+ struct list_head wait_list;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lockdep_map dep_map;
+#endif
+};
+
+#ifndef __s390x__
+#define RWSEM_UNLOCKED_VALUE 0x00000000
+#define RWSEM_ACTIVE_BIAS 0x00000001
+#define RWSEM_ACTIVE_MASK 0x0000ffff
+#define RWSEM_WAITING_BIAS (-0x00010000)
+#else /* __s390x__ */
+#define RWSEM_UNLOCKED_VALUE 0x0000000000000000L
+#define RWSEM_ACTIVE_BIAS 0x0000000000000001L
+#define RWSEM_ACTIVE_MASK 0x00000000ffffffffL
+#define RWSEM_WAITING_BIAS (-0x0000000100000000L)
+#endif /* __s390x__ */
+#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
+#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+
+/*
+ * initialisation
+ */
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
+#else
+# define __RWSEM_DEP_MAP_INIT(lockname)
+#endif
+
+#define __RWSEM_INITIALIZER(name) \
+ { RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait.lock), \
+ LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
+
+#define DECLARE_RWSEM(name) \
+ struct rw_semaphore name = __RWSEM_INITIALIZER(name)
+
+static inline void init_rwsem(struct rw_semaphore *sem)
+{
+ sem->count = RWSEM_UNLOCKED_VALUE;
+ spin_lock_init(&sem->wait_lock);
+ INIT_LIST_HEAD(&sem->wait_list);
+}
+
+extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
+ struct lock_class_key *key);
+
+#define init_rwsem(sem) \
+do { \
+ static struct lock_class_key __key; \
+ \
+ __init_rwsem((sem), #sem, &__key); \
+} while (0)
+
+
+/*
+ * lock for reading
+ */
+static inline void __down_read(struct rw_semaphore *sem)
+{
+ signed long old, new;
+
+ asm volatile(
+#ifndef __s390x__
+ " l %0,0(%3)\n"
+ "0: lr %1,%0\n"
+ " ahi %1,%5\n"
+ " cs %0,%1,0(%3)\n"
+ " jl 0b"
+#else /* __s390x__ */
+ " lg %0,0(%3)\n"
+ "0: lgr %1,%0\n"
+ " aghi %1,%5\n"
+ " csg %0,%1,0(%3)\n"
+ " jl 0b"
+#endif /* __s390x__ */
+ : "=&d" (old), "=&d" (new), "=m" (sem->count)
+ : "a" (&sem->count), "m" (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(
+#ifndef __s390x__
+ " l %0,0(%3)\n"
+ "0: ltr %1,%0\n"
+ " jm 1f\n"
+ " ahi %1,%5\n"
+ " cs %0,%1,0(%3)\n"
+ " jl 0b\n"
+ "1:"
+#else /* __s390x__ */
+ " lg %0,0(%3)\n"
+ "0: ltgr %1,%0\n"
+ " jm 1f\n"
+ " aghi %1,%5\n"
+ " csg %0,%1,0(%3)\n"
+ " jl 0b\n"
+ "1:"
+#endif /* __s390x__ */
+ : "=&d" (old), "=&d" (new), "=m" (sem->count)
+ : "a" (&sem->count), "m" (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(
+#ifndef __s390x__
+ " l %0,0(%3)\n"
+ "0: lr %1,%0\n"
+ " a %1,%5\n"
+ " cs %0,%1,0(%3)\n"
+ " jl 0b"
+#else /* __s390x__ */
+ " lg %0,0(%3)\n"
+ "0: lgr %1,%0\n"
+ " ag %1,%5\n"
+ " csg %0,%1,0(%3)\n"
+ " jl 0b"
+#endif /* __s390x__ */
+ : "=&d" (old), "=&d" (new), "=m" (sem->count)
+ : "a" (&sem->count), "m" (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(
+#ifndef __s390x__
+ " l %0,0(%2)\n"
+ "0: ltr %0,%0\n"
+ " jnz 1f\n"
+ " cs %0,%4,0(%2)\n"
+ " jl 0b\n"
+#else /* __s390x__ */
+ " lg %0,0(%2)\n"
+ "0: ltgr %0,%0\n"
+ " jnz 1f\n"
+ " csg %0,%4,0(%2)\n"
+ " jl 0b\n"
+#endif /* __s390x__ */
+ "1:"
+ : "=&d" (old), "=m" (sem->count)
+ : "a" (&sem->count), "m" (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(
+#ifndef __s390x__
+ " l %0,0(%3)\n"
+ "0: lr %1,%0\n"
+ " ahi %1,%5\n"
+ " cs %0,%1,0(%3)\n"
+ " jl 0b"
+#else /* __s390x__ */
+ " lg %0,0(%3)\n"
+ "0: lgr %1,%0\n"
+ " aghi %1,%5\n"
+ " csg %0,%1,0(%3)\n"
+ " jl 0b"
+#endif /* __s390x__ */
+ : "=&d" (old), "=&d" (new), "=m" (sem->count)
+ : "a" (&sem->count), "m" (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(
+#ifndef __s390x__
+ " l %0,0(%3)\n"
+ "0: lr %1,%0\n"
+ " a %1,%5\n"
+ " cs %0,%1,0(%3)\n"
+ " jl 0b"
+#else /* __s390x__ */
+ " lg %0,0(%3)\n"
+ "0: lgr %1,%0\n"
+ " ag %1,%5\n"
+ " csg %0,%1,0(%3)\n"
+ " jl 0b"
+#endif /* __s390x__ */
+ : "=&d" (old), "=&d" (new), "=m" (sem->count)
+ : "a" (&sem->count), "m" (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(
+#ifndef __s390x__
+ " l %0,0(%3)\n"
+ "0: lr %1,%0\n"
+ " a %1,%5\n"
+ " cs %0,%1,0(%3)\n"
+ " jl 0b"
+#else /* __s390x__ */
+ " lg %0,0(%3)\n"
+ "0: lgr %1,%0\n"
+ " ag %1,%5\n"
+ " csg %0,%1,0(%3)\n"
+ " jl 0b"
+#endif /* __s390x__ */
+ : "=&d" (old), "=&d" (new), "=m" (sem->count)
+ : "a" (&sem->count), "m" (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(
+#ifndef __s390x__
+ " l %0,0(%3)\n"
+ "0: lr %1,%0\n"
+ " ar %1,%5\n"
+ " cs %0,%1,0(%3)\n"
+ " jl 0b"
+#else /* __s390x__ */
+ " lg %0,0(%3)\n"
+ "0: lgr %1,%0\n"
+ " agr %1,%5\n"
+ " csg %0,%1,0(%3)\n"
+ " jl 0b"
+#endif /* __s390x__ */
+ : "=&d" (old), "=&d" (new), "=m" (sem->count)
+ : "a" (&sem->count), "m" (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(
+#ifndef __s390x__
+ " l %0,0(%3)\n"
+ "0: lr %1,%0\n"
+ " ar %1,%5\n"
+ " cs %0,%1,0(%3)\n"
+ " jl 0b"
+#else /* __s390x__ */
+ " lg %0,0(%3)\n"
+ "0: lgr %1,%0\n"
+ " agr %1,%5\n"
+ " csg %0,%1,0(%3)\n"
+ " jl 0b"
+#endif /* __s390x__ */
+ : "=&d" (old), "=&d" (new), "=m" (sem->count)
+ : "a" (&sem->count), "m" (sem->count), "d" (delta)
+ : "cc", "memory");
+ return new;
+}
+
+static inline int rwsem_is_locked(struct rw_semaphore *sem)
+{
+ return (sem->count != 0);
+}
+
+#endif /* __KERNEL__ */
+#endif /* _S390_RWSEM_H */
generated by cgit v1.2.3 (git 2.0.4) at 2024-11-08 22:39:38 +0000