#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__ 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 *); #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) /* * lock for reading */ static inline void __down_read(struct rw_semaphore *sem) { signed long old, new; asm volatile( #ifndef __s390x__ " l %0,%2\n" "0: lr %1,%0\n" " ahi %1,%4\n" " cs %0,%1,%2\n" " jl 0b" #else /* __s390x__ */ " lg %0,%2\n" "0: lgr %1,%0\n" " aghi %1,%4\n" " csg %0,%1,%2\n" " jl 0b" #endif /* __s390x__ */ : "=&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( #ifndef __s390x__ " l %0,%2\n" "0: ltr %1,%0\n" " jm 1f\n" " ahi %1,%4\n" " cs %0,%1,%2\n" " jl 0b\n" "1:" #else /* __s390x__ */ " 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:" #endif /* __s390x__ */ : "=&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( #ifndef __s390x__ " l %0,%2\n" "0: lr %1,%0\n" " a %1,%4\n" " cs %0,%1,%2\n" " jl 0b" #else /* __s390x__ */ " lg %0,%2\n" "0: lgr %1,%0\n" " ag %1,%4\n" " csg %0,%1,%2\n" " jl 0b" #endif /* __s390x__ */ : "=&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( #ifndef __s390x__ " l %0,%1\n" "0: ltr %0,%0\n" " jnz 1f\n" " cs %0,%3,%1\n" " jl 0b\n" #else /* __s390x__ */ " lg %0,%1\n" "0: ltgr %0,%0\n" " jnz 1f\n" " csg %0,%3,%1\n" " jl 0b\n" #endif /* __s390x__ */ "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( #ifndef __s390x__ " l %0,%2\n" "0: lr %1,%0\n" " ahi %1,%4\n" " cs %0,%1,%2\n" " jl 0b" #else /* __s390x__ */ " lg %0,%2\n" "0: lgr %1,%0\n" " aghi %1,%4\n" " csg %0,%1,%2\n" " jl 0b" #endif /* __s390x__ */ : "=&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( #ifndef __s390x__ " l %0,%2\n" "0: lr %1,%0\n" " a %1,%4\n" " cs %0,%1,%2\n" " jl 0b" #else /* __s390x__ */ " lg %0,%2\n" "0: lgr %1,%0\n" " ag %1,%4\n" " csg %0,%1,%2\n" " jl 0b" #endif /* __s390x__ */ : "=&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( #ifndef __s390x__ " l %0,%2\n" "0: lr %1,%0\n" " a %1,%4\n" " cs %0,%1,%2\n" " jl 0b" #else /* __s390x__ */ " lg %0,%2\n" "0: lgr %1,%0\n" " ag %1,%4\n" " csg %0,%1,%2\n" " jl 0b" #endif /* __s390x__ */ : "=&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( #ifndef __s390x__ " l %0,%2\n" "0: lr %1,%0\n" " ar %1,%4\n" " cs %0,%1,%2\n" " jl 0b" #else /* __s390x__ */ " lg %0,%2\n" "0: lgr %1,%0\n" " agr %1,%4\n" " csg %0,%1,%2\n" " jl 0b" #endif /* __s390x__ */ : "=&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( #ifndef __s390x__ " l %0,%2\n" "0: lr %1,%0\n" " ar %1,%4\n" " cs %0,%1,%2\n" " jl 0b" #else /* __s390x__ */ " lg %0,%2\n" "0: lgr %1,%0\n" " agr %1,%4\n" " csg %0,%1,%2\n" " jl 0b" #endif /* __s390x__ */ : "=&d" (old), "=&d" (new), "=Q" (sem->count) : "Q" (sem->count), "d" (delta) : "cc", "memory"); return new; } #endif /* __KERNEL__ */ #endif /* _S390_RWSEM_H */