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linux/arch/s390/include/asm/rwsem.h
Martin Schwidefsky 987bcdacb1 [S390] use inline assembly contraints available with gcc 3.3.3 
Drop support to compile the kernel with gcc versions older than 3.3.3.
This allows us to use the "Q" inline assembly contraint on some more
inline assemblies without duplicating a lot of complex code (e.g. __xchg
and __cmpxchg). The distinction for older gcc versions can be removed
which saves a few lines and simplifies the code.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2010-02-26 22:37:30 +01:00

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8.6 KiB
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#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,%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;
}
static inline int rwsem_is_locked(struct rw_semaphore *sem)
{
return (sem->count != 0);
}
#endif /* __KERNEL__ */
#endif /* _S390_RWSEM_H */
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