ia64/linux-2.6.18-xen.hg

view arch/mips/kernel/semaphore.c @ 452:c7ed6fe5dca0

kexec: dont initialise regions in reserve_memory()

There is no need to initialise efi_memmap_res and boot_param_res in
reserve_memory() for the initial xen domain as it is done in
machine_kexec_setup_resources() using values from the kexec hypercall.

Signed-off-by: Simon Horman <horms@verge.net.au>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Feb 28 10:55:18 2008 +0000 (2008-02-28)
parents 831230e53067
children
line source
1 /*
2 * MIPS-specific semaphore code.
3 *
4 * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu>
5 * Copyright (C) 2004 Ralf Baechle <ralf@linux-mips.org>
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 * April 2001 - Reworked by Paul Mackerras <paulus@samba.org>
13 * to eliminate the SMP races in the old version between the updates
14 * of `count' and `waking'. Now we use negative `count' values to
15 * indicate that some process(es) are waiting for the semaphore.
16 */
18 #include <linux/module.h>
19 #include <linux/sched.h>
20 #include <linux/init.h>
21 #include <asm/atomic.h>
22 #include <asm/cpu-features.h>
23 #include <asm/errno.h>
24 #include <asm/semaphore.h>
25 #include <asm/war.h>
26 /*
27 * Atomically update sem->count.
28 * This does the equivalent of the following:
29 *
30 * old_count = sem->count;
31 * tmp = MAX(old_count, 0) + incr;
32 * sem->count = tmp;
33 * return old_count;
34 *
35 * On machines without lld/scd we need a spinlock to make the manipulation of
36 * sem->count and sem->waking atomic. Scalability isn't an issue because
37 * this lock is used on UP only so it's just an empty variable.
38 */
39 static inline int __sem_update_count(struct semaphore *sem, int incr)
40 {
41 int old_count, tmp;
43 if (cpu_has_llsc && R10000_LLSC_WAR) {
44 __asm__ __volatile__(
45 " .set mips3 \n"
46 "1: ll %0, %2 # __sem_update_count \n"
47 " sra %1, %0, 31 \n"
48 " not %1 \n"
49 " and %1, %0, %1 \n"
50 " addu %1, %1, %3 \n"
51 " sc %1, %2 \n"
52 " beqzl %1, 1b \n"
53 " .set mips0 \n"
54 : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
55 : "r" (incr), "m" (sem->count));
56 } else if (cpu_has_llsc) {
57 __asm__ __volatile__(
58 " .set mips3 \n"
59 "1: ll %0, %2 # __sem_update_count \n"
60 " sra %1, %0, 31 \n"
61 " not %1 \n"
62 " and %1, %0, %1 \n"
63 " addu %1, %1, %3 \n"
64 " sc %1, %2 \n"
65 " beqz %1, 1b \n"
66 " .set mips0 \n"
67 : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
68 : "r" (incr), "m" (sem->count));
69 } else {
70 static DEFINE_SPINLOCK(semaphore_lock);
71 unsigned long flags;
73 spin_lock_irqsave(&semaphore_lock, flags);
74 old_count = atomic_read(&sem->count);
75 tmp = max_t(int, old_count, 0) + incr;
76 atomic_set(&sem->count, tmp);
77 spin_unlock_irqrestore(&semaphore_lock, flags);
78 }
80 return old_count;
81 }
83 void __up(struct semaphore *sem)
84 {
85 /*
86 * Note that we incremented count in up() before we came here,
87 * but that was ineffective since the result was <= 0, and
88 * any negative value of count is equivalent to 0.
89 * This ends up setting count to 1, unless count is now > 0
90 * (i.e. because some other cpu has called up() in the meantime),
91 * in which case we just increment count.
92 */
93 __sem_update_count(sem, 1);
94 wake_up(&sem->wait);
95 }
97 EXPORT_SYMBOL(__up);
99 /*
100 * Note that when we come in to __down or __down_interruptible,
101 * we have already decremented count, but that decrement was
102 * ineffective since the result was < 0, and any negative value
103 * of count is equivalent to 0.
104 * Thus it is only when we decrement count from some value > 0
105 * that we have actually got the semaphore.
106 */
107 void __sched __down(struct semaphore *sem)
108 {
109 struct task_struct *tsk = current;
110 DECLARE_WAITQUEUE(wait, tsk);
112 __set_task_state(tsk, TASK_UNINTERRUPTIBLE);
113 add_wait_queue_exclusive(&sem->wait, &wait);
115 /*
116 * Try to get the semaphore. If the count is > 0, then we've
117 * got the semaphore; we decrement count and exit the loop.
118 * If the count is 0 or negative, we set it to -1, indicating
119 * that we are asleep, and then sleep.
120 */
121 while (__sem_update_count(sem, -1) <= 0) {
122 schedule();
123 set_task_state(tsk, TASK_UNINTERRUPTIBLE);
124 }
125 remove_wait_queue(&sem->wait, &wait);
126 __set_task_state(tsk, TASK_RUNNING);
128 /*
129 * If there are any more sleepers, wake one of them up so
130 * that it can either get the semaphore, or set count to -1
131 * indicating that there are still processes sleeping.
132 */
133 wake_up(&sem->wait);
134 }
136 EXPORT_SYMBOL(__down);
138 int __sched __down_interruptible(struct semaphore * sem)
139 {
140 int retval = 0;
141 struct task_struct *tsk = current;
142 DECLARE_WAITQUEUE(wait, tsk);
144 __set_task_state(tsk, TASK_INTERRUPTIBLE);
145 add_wait_queue_exclusive(&sem->wait, &wait);
147 while (__sem_update_count(sem, -1) <= 0) {
148 if (signal_pending(current)) {
149 /*
150 * A signal is pending - give up trying.
151 * Set sem->count to 0 if it is negative,
152 * since we are no longer sleeping.
153 */
154 __sem_update_count(sem, 0);
155 retval = -EINTR;
156 break;
157 }
158 schedule();
159 set_task_state(tsk, TASK_INTERRUPTIBLE);
160 }
161 remove_wait_queue(&sem->wait, &wait);
162 __set_task_state(tsk, TASK_RUNNING);
164 wake_up(&sem->wait);
165 return retval;
166 }
168 EXPORT_SYMBOL(__down_interruptible);