Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 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 | |
Arun Sharma | 60063497 | 2011-07-26 16:09:06 -0700 | [diff] [blame] | 20 | #include <linux/atomic.h> |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 21 | #include <asm/page.h> |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 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 | */ |
| 36 | static 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. |
Chris Metcalf | 627ae54 | 2015-04-28 13:00:42 -0400 | [diff] [blame] | 44 | * Use READ_ONCE() to ensure that calling this in a loop is OK. |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 45 | */ |
Chris Metcalf | 627ae54 | 2015-04-28 13:00:42 -0400 | [diff] [blame] | 46 | int curr = READ_ONCE(lock->current_ticket); |
| 47 | int next = READ_ONCE(lock->next_ticket); |
| 48 | |
| 49 | return next != curr; |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 50 | } |
| 51 | |
| 52 | void arch_spin_lock(arch_spinlock_t *lock); |
| 53 | |
| 54 | /* We cannot take an interrupt after getting a ticket, so don't enable them. */ |
| 55 | #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock) |
| 56 | |
| 57 | int arch_spin_trylock(arch_spinlock_t *lock); |
| 58 | |
| 59 | static inline void arch_spin_unlock(arch_spinlock_t *lock) |
| 60 | { |
| 61 | /* For efficiency, overlap fetching the old ticket with the wmb(). */ |
| 62 | int old_ticket = lock->current_ticket; |
| 63 | wmb(); /* guarantee anything modified under the lock is visible */ |
| 64 | lock->current_ticket = old_ticket + TICKET_QUANTUM; |
| 65 | } |
| 66 | |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 67 | /* |
| 68 | * Read-write spinlocks, allowing multiple readers |
| 69 | * but only one writer. |
| 70 | * |
| 71 | * We use a "tns/store-back" technique on a single word to manage |
| 72 | * the lock state, looping around to retry if the tns returns 1. |
| 73 | */ |
| 74 | |
| 75 | /* Internal layout of the word; do not use. */ |
| 76 | #define _WR_NEXT_SHIFT 8 |
| 77 | #define _WR_CURR_SHIFT 16 |
| 78 | #define _WR_WIDTH 8 |
| 79 | #define _RD_COUNT_SHIFT 24 |
| 80 | #define _RD_COUNT_WIDTH 8 |
| 81 | |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 82 | /** |
| 83 | * arch_read_can_lock() - would read_trylock() succeed? |
| 84 | */ |
| 85 | static inline int arch_read_can_lock(arch_rwlock_t *rwlock) |
| 86 | { |
| 87 | return (rwlock->lock << _RD_COUNT_WIDTH) == 0; |
| 88 | } |
| 89 | |
| 90 | /** |
| 91 | * arch_write_can_lock() - would write_trylock() succeed? |
| 92 | */ |
| 93 | static inline int arch_write_can_lock(arch_rwlock_t *rwlock) |
| 94 | { |
| 95 | return rwlock->lock == 0; |
| 96 | } |
| 97 | |
| 98 | /** |
| 99 | * arch_read_lock() - acquire a read lock. |
| 100 | */ |
Chris Metcalf | 3c5ead5 | 2011-03-01 13:30:15 -0500 | [diff] [blame] | 101 | void arch_read_lock(arch_rwlock_t *rwlock); |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 102 | |
| 103 | /** |
Chris Metcalf | 3c5ead5 | 2011-03-01 13:30:15 -0500 | [diff] [blame] | 104 | * arch_write_lock() - acquire a write lock. |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 105 | */ |
Chris Metcalf | 3c5ead5 | 2011-03-01 13:30:15 -0500 | [diff] [blame] | 106 | void arch_write_lock(arch_rwlock_t *rwlock); |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 107 | |
| 108 | /** |
| 109 | * arch_read_trylock() - try to acquire a read lock. |
| 110 | */ |
Chris Metcalf | 3c5ead5 | 2011-03-01 13:30:15 -0500 | [diff] [blame] | 111 | int arch_read_trylock(arch_rwlock_t *rwlock); |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 112 | |
| 113 | /** |
| 114 | * arch_write_trylock() - try to acquire a write lock. |
| 115 | */ |
Chris Metcalf | 3c5ead5 | 2011-03-01 13:30:15 -0500 | [diff] [blame] | 116 | int arch_write_trylock(arch_rwlock_t *rwlock); |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 117 | |
| 118 | /** |
| 119 | * arch_read_unlock() - release a read lock. |
| 120 | */ |
Chris Metcalf | 3c5ead5 | 2011-03-01 13:30:15 -0500 | [diff] [blame] | 121 | void arch_read_unlock(arch_rwlock_t *rwlock); |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 122 | |
| 123 | /** |
| 124 | * arch_write_unlock() - release a write lock. |
| 125 | */ |
Chris Metcalf | 3c5ead5 | 2011-03-01 13:30:15 -0500 | [diff] [blame] | 126 | void arch_write_unlock(arch_rwlock_t *rwlock); |
Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 127 | |
| 128 | #define arch_read_lock_flags(lock, flags) arch_read_lock(lock) |
| 129 | #define arch_write_lock_flags(lock, flags) arch_write_lock(lock) |
| 130 | |
| 131 | #endif /* _ASM_TILE_SPINLOCK_32_H */ |