mirror of
https://github.com/torvalds/linux.git
synced 2024-11-16 00:52:01 +00:00
eb92f4ef32
Add sem_is_read/write_locked functions to the read/write semaphores, along the same lines of the *_is_locked spinlock functions. The swap token tuning patch uses sem_is_read_locked; sem_is_write_locked is added for completeness. Signed-off-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
361 lines
8.7 KiB
C
361 lines
8.7 KiB
C
#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;
|
|
}
|
|
|
|
static inline int rwsem_is_locked(struct rw_semaphore *sem)
|
|
{
|
|
return (sem->count != 0);
|
|
}
|
|
|
|
#endif /* __KERNEL__ */
|
|
#endif /* _S390_RWSEM_H */
|