Viewing file:  spinlock.h (2.45 KB) -rw-r--r--
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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (C) 2015 Regents of the University of California
* Copyright (C) 2017 SiFive
*/
#ifndef _ASM_RISCV_SPINLOCK_H
#define _ASM_RISCV_SPINLOCK_H
#include <linux/kernel.h>
#include <asm/current.h>
#include <asm/fence.h>
/*
* Simple spin lock operations. These provide no fairness guarantees.
*/
/* FIXME: Replace this with a ticket lock, like MIPS. */
#define arch_spin_is_locked(x) (READ_ONCE((x)->lock) != 0)
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
smp_store_release(&lock->lock, 0);
}
static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
int tmp = 1, busy;
__asm__ __volatile__ (
" amoswap.w %0, %2, %1\n"
RISCV_ACQUIRE_BARRIER
: "=r" (busy), "+A" (lock->lock)
: "r" (tmp)
: "memory");
return !busy;
}
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
while (1) {
if (arch_spin_is_locked(lock))
continue;
if (arch_spin_trylock(lock))
break;
}
}
/***********************************************************/
static inline void arch_read_lock(arch_rwlock_t *lock)
{
int tmp;
__asm__ __volatile__(
"1: lr.w %1, %0\n"
" bltz %1, 1b\n"
" addi %1, %1, 1\n"
" sc.w %1, %1, %0\n"
" bnez %1, 1b\n"
RISCV_ACQUIRE_BARRIER
: "+A" (lock->lock), "=&r" (tmp)
:: "memory");
}
static inline void arch_write_lock(arch_rwlock_t *lock)
{
int tmp;
__asm__ __volatile__(
"1: lr.w %1, %0\n"
" bnez %1, 1b\n"
" li %1, -1\n"
" sc.w %1, %1, %0\n"
" bnez %1, 1b\n"
RISCV_ACQUIRE_BARRIER
: "+A" (lock->lock), "=&r" (tmp)
:: "memory");
}
static inline int arch_read_trylock(arch_rwlock_t *lock)
{
int busy;
__asm__ __volatile__(
"1: lr.w %1, %0\n"
" bltz %1, 1f\n"
" addi %1, %1, 1\n"
" sc.w %1, %1, %0\n"
" bnez %1, 1b\n"
RISCV_ACQUIRE_BARRIER
"1:\n"
: "+A" (lock->lock), "=&r" (busy)
:: "memory");
return !busy;
}
static inline int arch_write_trylock(arch_rwlock_t *lock)
{
int busy;
__asm__ __volatile__(
"1: lr.w %1, %0\n"
" bnez %1, 1f\n"
" li %1, -1\n"
" sc.w %1, %1, %0\n"
" bnez %1, 1b\n"
RISCV_ACQUIRE_BARRIER
"1:\n"
: "+A" (lock->lock), "=&r" (busy)
:: "memory");
return !busy;
}
static inline void arch_read_unlock(arch_rwlock_t *lock)
{
__asm__ __volatile__(
RISCV_RELEASE_BARRIER
" amoadd.w x0, %1, %0\n"
: "+A" (lock->lock)
: "r" (-1)
: "memory");
}
static inline void arch_write_unlock(arch_rwlock_t *lock)
{
smp_store_release(&lock->lock, 0);
}
#endif /* _ASM_RISCV_SPINLOCK_H */
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