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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /include/asm-s390/rwsem.h | |
download | lwn-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz lwn-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'include/asm-s390/rwsem.h')
-rw-r--r-- | include/asm-s390/rwsem.h | 355 |
1 files changed, 355 insertions, 0 deletions
diff --git a/include/asm-s390/rwsem.h b/include/asm-s390/rwsem.h new file mode 100644 index 000000000000..8c0cebbfc034 --- /dev/null +++ b/include/asm-s390/rwsem.h @@ -0,0 +1,355 @@ +#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 */ |