1/* 2 * Copyright 2010 Tilera Corporation. All Rights Reserved. 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License 6 * as published by the Free Software Foundation, version 2. 7 * 8 * This program is distributed in the hope that it will be useful, but 9 * WITHOUT ANY WARRANTY; without even the implied warranty of 10 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or 11 * NON INFRINGEMENT. See the GNU General Public License for 12 * more details. 13 * 14 * 32-bit SMP spinlocks. 15 */ 16 17#ifndef _ASM_TILE_SPINLOCK_32_H 18#define _ASM_TILE_SPINLOCK_32_H 19 20#include <linux/atomic.h> 21#include <asm/page.h> 22#include <linux/compiler.h> 23 24/* 25 * We only use even ticket numbers so the '1' inserted by a tns is 26 * an unambiguous "ticket is busy" flag. 27 */ 28#define TICKET_QUANTUM 2 29 30 31/* 32 * SMP ticket spinlocks, allowing only a single CPU anywhere 33 * 34 * (the type definitions are in asm/spinlock_types.h) 35 */ 36static inline int arch_spin_is_locked(arch_spinlock_t *lock) 37{ 38 /* 39 * Note that even if a new ticket is in the process of being 40 * acquired, so lock->next_ticket is 1, it's still reasonable 41 * to claim the lock is held, since it will be momentarily 42 * if not already. There's no need to wait for a "valid" 43 * lock->next_ticket to become available. 44 */ 45 return lock->next_ticket != lock->current_ticket; 46} 47 48void arch_spin_lock(arch_spinlock_t *lock); 49 50/* We cannot take an interrupt after getting a ticket, so don't enable them. */ 51#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock) 52 53int arch_spin_trylock(arch_spinlock_t *lock); 54 55static inline void arch_spin_unlock(arch_spinlock_t *lock) 56{ 57 /* For efficiency, overlap fetching the old ticket with the wmb(). */ 58 int old_ticket = lock->current_ticket; 59 wmb(); /* guarantee anything modified under the lock is visible */ 60 lock->current_ticket = old_ticket + TICKET_QUANTUM; 61} 62 63void arch_spin_unlock_wait(arch_spinlock_t *lock); 64 65/* 66 * Read-write spinlocks, allowing multiple readers 67 * but only one writer. 68 * 69 * We use a "tns/store-back" technique on a single word to manage 70 * the lock state, looping around to retry if the tns returns 1. 71 */ 72 73/* Internal layout of the word; do not use. */ 74#define _WR_NEXT_SHIFT 8 75#define _WR_CURR_SHIFT 16 76#define _WR_WIDTH 8 77#define _RD_COUNT_SHIFT 24 78#define _RD_COUNT_WIDTH 8 79 80/** 81 * arch_read_can_lock() - would read_trylock() succeed? 82 */ 83static inline int arch_read_can_lock(arch_rwlock_t *rwlock) 84{ 85 return (rwlock->lock << _RD_COUNT_WIDTH) == 0; 86} 87 88/** 89 * arch_write_can_lock() - would write_trylock() succeed? 90 */ 91static inline int arch_write_can_lock(arch_rwlock_t *rwlock) 92{ 93 return rwlock->lock == 0; 94} 95 96/** 97 * arch_read_lock() - acquire a read lock. 98 */ 99void arch_read_lock(arch_rwlock_t *rwlock); 100 101/** 102 * arch_write_lock() - acquire a write lock. 103 */ 104void arch_write_lock(arch_rwlock_t *rwlock); 105 106/** 107 * arch_read_trylock() - try to acquire a read lock. 108 */ 109int arch_read_trylock(arch_rwlock_t *rwlock); 110 111/** 112 * arch_write_trylock() - try to acquire a write lock. 113 */ 114int arch_write_trylock(arch_rwlock_t *rwlock); 115 116/** 117 * arch_read_unlock() - release a read lock. 118 */ 119void arch_read_unlock(arch_rwlock_t *rwlock); 120 121/** 122 * arch_write_unlock() - release a write lock. 123 */ 124void arch_write_unlock(arch_rwlock_t *rwlock); 125 126#define arch_read_lock_flags(lock, flags) arch_read_lock(lock) 127#define arch_write_lock_flags(lock, flags) arch_write_lock(lock) 128 129#endif /* _ASM_TILE_SPINLOCK_32_H */ 130