58 lines
1.2 KiB
C
58 lines
1.2 KiB
C
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/* vim: tabstop=4 shiftwidth=4 noexpandtab
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* This file is part of ToaruOS and is released under the terms
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* of the NCSA / University of Illinois License - see LICENSE.md
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* Copyright (C) 2015 Dale Weiler
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*
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* Spin locks with waiters
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*
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*/
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#include <system.h>
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static inline int arch_atomic_swap(volatile int * x, int v) {
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asm("xchg %0, %1" : "=r"(v), "=m"(*x) : "0"(v) : "memory");
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return v;
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}
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static inline void arch_atomic_store(volatile int * p, int x) {
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asm("movl %1, %0" : "=m"(*p) : "r"(x) : "memory");
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}
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static inline void arch_atomic_inc(volatile int * x) {
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asm("lock; incl %0" : "=m"(*x) : "m"(*x) : "memory");
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}
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static inline void arch_atomic_dec(volatile int * x) {
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asm("lock; decl %0" : "=m"(*x) : "m"(*x) : "memory");
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}
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void spin_wait(volatile int * addr, volatile int * waiters) {
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if (waiters) {
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arch_atomic_inc(waiters);
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}
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while (*addr) {
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switch_task(1);
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}
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if (waiters) {
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arch_atomic_dec(waiters);
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}
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}
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void spin_lock(spin_lock_t lock) {
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while (arch_atomic_swap(lock, 1)) {
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spin_wait(lock, lock+1);
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}
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}
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void spin_init(spin_lock_t lock) {
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lock[0] = 0;
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lock[1] = 0;
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}
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void spin_unlock(spin_lock_t lock) {
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if (lock[0]) {
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arch_atomic_store(lock, 0);
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if (lock[1])
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switch_task(1);
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}
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}
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