6e35fa2d43
Signed-off-by: Vineet Gupta <vgupta@synopsys.com> Acked-by: Arnd Bergmann <arnd@arndb.de>
144 lines
3.4 KiB
C
144 lines
3.4 KiB
C
/*
|
|
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
|
|
#ifndef __ASM_SPINLOCK_H
|
|
#define __ASM_SPINLOCK_H
|
|
|
|
#include <asm/spinlock_types.h>
|
|
#include <asm/processor.h>
|
|
#include <asm/barrier.h>
|
|
|
|
#define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
|
|
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
|
|
#define arch_spin_unlock_wait(x) \
|
|
do { while (arch_spin_is_locked(x)) cpu_relax(); } while (0)
|
|
|
|
static inline void arch_spin_lock(arch_spinlock_t *lock)
|
|
{
|
|
unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
|
|
|
|
__asm__ __volatile__(
|
|
"1: ex %0, [%1] \n"
|
|
" breq %0, %2, 1b \n"
|
|
: "+&r" (tmp)
|
|
: "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
|
|
: "memory");
|
|
}
|
|
|
|
static inline int arch_spin_trylock(arch_spinlock_t *lock)
|
|
{
|
|
unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
|
|
|
|
__asm__ __volatile__(
|
|
"1: ex %0, [%1] \n"
|
|
: "+r" (tmp)
|
|
: "r"(&(lock->slock))
|
|
: "memory");
|
|
|
|
return (tmp == __ARCH_SPIN_LOCK_UNLOCKED__);
|
|
}
|
|
|
|
static inline void arch_spin_unlock(arch_spinlock_t *lock)
|
|
{
|
|
lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__;
|
|
smp_mb();
|
|
}
|
|
|
|
/*
|
|
* Read-write spinlocks, allowing multiple readers but only one writer.
|
|
*
|
|
* The spinlock itself is contained in @counter and access to it is
|
|
* serialized with @lock_mutex.
|
|
*
|
|
* Unfair locking as Writers could be starved indefinitely by Reader(s)
|
|
*/
|
|
|
|
/* Would read_trylock() succeed? */
|
|
#define arch_read_can_lock(x) ((x)->counter > 0)
|
|
|
|
/* Would write_trylock() succeed? */
|
|
#define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__)
|
|
|
|
/* 1 - lock taken successfully */
|
|
static inline int arch_read_trylock(arch_rwlock_t *rw)
|
|
{
|
|
int ret = 0;
|
|
|
|
arch_spin_lock(&(rw->lock_mutex));
|
|
|
|
/*
|
|
* zero means writer holds the lock exclusively, deny Reader.
|
|
* Otherwise grant lock to first/subseq reader
|
|
*/
|
|
if (rw->counter > 0) {
|
|
rw->counter--;
|
|
ret = 1;
|
|
}
|
|
|
|
arch_spin_unlock(&(rw->lock_mutex));
|
|
|
|
smp_mb();
|
|
return ret;
|
|
}
|
|
|
|
/* 1 - lock taken successfully */
|
|
static inline int arch_write_trylock(arch_rwlock_t *rw)
|
|
{
|
|
int ret = 0;
|
|
|
|
arch_spin_lock(&(rw->lock_mutex));
|
|
|
|
/*
|
|
* If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
|
|
* deny writer. Otherwise if unlocked grant to writer
|
|
* Hence the claim that Linux rwlocks are unfair to writers.
|
|
* (can be starved for an indefinite time by readers).
|
|
*/
|
|
if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
|
|
rw->counter = 0;
|
|
ret = 1;
|
|
}
|
|
arch_spin_unlock(&(rw->lock_mutex));
|
|
|
|
return ret;
|
|
}
|
|
|
|
static inline void arch_read_lock(arch_rwlock_t *rw)
|
|
{
|
|
while (!arch_read_trylock(rw))
|
|
cpu_relax();
|
|
}
|
|
|
|
static inline void arch_write_lock(arch_rwlock_t *rw)
|
|
{
|
|
while (!arch_write_trylock(rw))
|
|
cpu_relax();
|
|
}
|
|
|
|
static inline void arch_read_unlock(arch_rwlock_t *rw)
|
|
{
|
|
arch_spin_lock(&(rw->lock_mutex));
|
|
rw->counter++;
|
|
arch_spin_unlock(&(rw->lock_mutex));
|
|
}
|
|
|
|
static inline void arch_write_unlock(arch_rwlock_t *rw)
|
|
{
|
|
arch_spin_lock(&(rw->lock_mutex));
|
|
rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
|
|
arch_spin_unlock(&(rw->lock_mutex));
|
|
}
|
|
|
|
#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
|
|
#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
|
|
|
|
#define arch_spin_relax(lock) cpu_relax()
|
|
#define arch_read_relax(lock) cpu_relax()
|
|
#define arch_write_relax(lock) cpu_relax()
|
|
|
|
#endif /* __ASM_SPINLOCK_H */
|