Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* semaphore.c: FR-V semaphores |
| 2 | * |
| 3 | * Copyright (C) 2003 Red Hat, Inc. All Rights Reserved. |
| 4 | * Written by David Howells (dhowells@redhat.com) |
| 5 | * - Derived from lib/rwsem-spinlock.c |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or |
| 8 | * modify it under the terms of the GNU General Public License |
| 9 | * as published by the Free Software Foundation; either version |
| 10 | * 2 of the License, or (at your option) any later version. |
| 11 | */ |
| 12 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 13 | #include <linux/sched.h> |
| 14 | #include <linux/module.h> |
| 15 | #include <asm/semaphore.h> |
| 16 | |
| 17 | struct sem_waiter { |
| 18 | struct list_head list; |
| 19 | struct task_struct *task; |
| 20 | }; |
| 21 | |
David Howells | 8080f23 | 2005-11-28 13:43:51 -0800 | [diff] [blame] | 22 | #if SEMAPHORE_DEBUG |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 23 | void semtrace(struct semaphore *sem, const char *str) |
| 24 | { |
| 25 | if (sem->debug) |
| 26 | printk("[%d] %s({%d,%d})\n", |
| 27 | current->pid, |
| 28 | str, |
| 29 | sem->counter, |
| 30 | list_empty(&sem->wait_list) ? 0 : 1); |
| 31 | } |
| 32 | #else |
| 33 | #define semtrace(SEM,STR) do { } while(0) |
| 34 | #endif |
| 35 | |
| 36 | /* |
| 37 | * wait for a token to be granted from a semaphore |
| 38 | * - entered with lock held and interrupts disabled |
| 39 | */ |
| 40 | void __down(struct semaphore *sem, unsigned long flags) |
| 41 | { |
| 42 | struct task_struct *tsk = current; |
| 43 | struct sem_waiter waiter; |
| 44 | |
| 45 | semtrace(sem, "Entering __down"); |
| 46 | |
| 47 | /* set up my own style of waitqueue */ |
| 48 | waiter.task = tsk; |
| 49 | get_task_struct(tsk); |
| 50 | |
| 51 | list_add_tail(&waiter.list, &sem->wait_list); |
| 52 | |
| 53 | /* we don't need to touch the semaphore struct anymore */ |
| 54 | spin_unlock_irqrestore(&sem->wait_lock, flags); |
| 55 | |
| 56 | /* wait to be given the semaphore */ |
| 57 | set_task_state(tsk, TASK_UNINTERRUPTIBLE); |
| 58 | |
| 59 | for (;;) { |
| 60 | if (list_empty(&waiter.list)) |
| 61 | break; |
| 62 | schedule(); |
| 63 | set_task_state(tsk, TASK_UNINTERRUPTIBLE); |
| 64 | } |
| 65 | |
| 66 | tsk->state = TASK_RUNNING; |
| 67 | semtrace(sem, "Leaving __down"); |
| 68 | } |
| 69 | |
| 70 | EXPORT_SYMBOL(__down); |
| 71 | |
| 72 | /* |
| 73 | * interruptibly wait for a token to be granted from a semaphore |
| 74 | * - entered with lock held and interrupts disabled |
| 75 | */ |
| 76 | int __down_interruptible(struct semaphore *sem, unsigned long flags) |
| 77 | { |
| 78 | struct task_struct *tsk = current; |
| 79 | struct sem_waiter waiter; |
| 80 | int ret; |
| 81 | |
| 82 | semtrace(sem,"Entering __down_interruptible"); |
| 83 | |
| 84 | /* set up my own style of waitqueue */ |
| 85 | waiter.task = tsk; |
| 86 | get_task_struct(tsk); |
| 87 | |
| 88 | list_add_tail(&waiter.list, &sem->wait_list); |
| 89 | |
| 90 | /* we don't need to touch the semaphore struct anymore */ |
| 91 | set_task_state(tsk, TASK_INTERRUPTIBLE); |
| 92 | |
| 93 | spin_unlock_irqrestore(&sem->wait_lock, flags); |
| 94 | |
| 95 | /* wait to be given the semaphore */ |
| 96 | ret = 0; |
| 97 | for (;;) { |
| 98 | if (list_empty(&waiter.list)) |
| 99 | break; |
| 100 | if (unlikely(signal_pending(current))) |
| 101 | goto interrupted; |
| 102 | schedule(); |
| 103 | set_task_state(tsk, TASK_INTERRUPTIBLE); |
| 104 | } |
| 105 | |
| 106 | out: |
| 107 | tsk->state = TASK_RUNNING; |
| 108 | semtrace(sem, "Leaving __down_interruptible"); |
| 109 | return ret; |
| 110 | |
| 111 | interrupted: |
| 112 | spin_lock_irqsave(&sem->wait_lock, flags); |
| 113 | |
| 114 | if (!list_empty(&waiter.list)) { |
| 115 | list_del(&waiter.list); |
| 116 | ret = -EINTR; |
| 117 | } |
| 118 | |
| 119 | spin_unlock_irqrestore(&sem->wait_lock, flags); |
| 120 | if (ret == -EINTR) |
| 121 | put_task_struct(current); |
| 122 | goto out; |
| 123 | } |
| 124 | |
| 125 | EXPORT_SYMBOL(__down_interruptible); |
| 126 | |
| 127 | /* |
| 128 | * release a single token back to a semaphore |
| 129 | * - entered with lock held and interrupts disabled |
| 130 | */ |
| 131 | void __up(struct semaphore *sem) |
| 132 | { |
| 133 | struct task_struct *tsk; |
| 134 | struct sem_waiter *waiter; |
| 135 | |
| 136 | semtrace(sem,"Entering __up"); |
| 137 | |
| 138 | /* grant the token to the process at the front of the queue */ |
| 139 | waiter = list_entry(sem->wait_list.next, struct sem_waiter, list); |
| 140 | |
| 141 | /* We must be careful not to touch 'waiter' after we set ->task = NULL. |
| 142 | * It is an allocated on the waiter's stack and may become invalid at |
| 143 | * any time after that point (due to a wakeup from another source). |
| 144 | */ |
| 145 | list_del_init(&waiter->list); |
| 146 | tsk = waiter->task; |
| 147 | mb(); |
| 148 | waiter->task = NULL; |
| 149 | wake_up_process(tsk); |
| 150 | put_task_struct(tsk); |
| 151 | |
| 152 | semtrace(sem,"Leaving __up"); |
| 153 | } |
| 154 | |
| 155 | EXPORT_SYMBOL(__up); |