| #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; |
| }; |
| |
| #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 |
| */ |
| #define __RWSEM_INITIALIZER(name) \ |
| { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) } |
| |
| #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); |
| } |
| |
| /* |
| * 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(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 (old != 0) |
| rwsem_down_write_failed(sem); |
| } |
| |
| /* |
| * 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; |
| } |
| |
| #endif /* __KERNEL__ */ |
| #endif /* _S390_RWSEM_H */ |