1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
|
#ifndef _LINUX_CONDVAR_H
#define _LINUX_CONDVAR_H
#ifdef __cplusplus
extern "C" {
#endif
#include <linux/wait.h>
/* The kcondvar_t struct is protected by mutex taken externally before
* calling any of the wait/signal funs, and passed into the wait funs.
*/
#define CV_MAGIC 0x346545f4
#define CV_POISON 0x95
typedef struct {
int cv_magic;
char *cv_name;
wait_queue_head_t cv_event;
atomic_t cv_waiters;
kmutex_t *cv_mutex; /* only for verification purposes */
} kcondvar_t;
typedef enum { CV_DEFAULT=0, CV_DRIVER } kcv_type_t;
static __inline__ void
cv_init(kcondvar_t *cvp, char *name, kcv_type_t type, void *arg)
{
BUG_ON(cvp == NULL);
BUG_ON(type != CV_DEFAULT);
BUG_ON(arg != NULL);
cvp->cv_magic = CV_MAGIC;
init_waitqueue_head(&cvp->cv_event);
atomic_set(&cvp->cv_waiters, 0);
cvp->cv_mutex = NULL;
cvp->cv_name = NULL;
if (name) {
cvp->cv_name = kmalloc(strlen(name) + 1, GFP_KERNEL);
if (cvp->cv_name)
strcpy(cvp->cv_name, name);
}
}
static __inline__ void
cv_destroy(kcondvar_t *cvp)
{
BUG_ON(cvp == NULL);
BUG_ON(cvp->cv_magic != CV_MAGIC);
BUG_ON(atomic_read(&cvp->cv_waiters) != 0);
BUG_ON(waitqueue_active(&cvp->cv_event));
if (cvp->cv_name)
kfree(cvp->cv_name);
memset(cvp, CV_POISON, sizeof(*cvp));
}
static __inline__ void
cv_wait(kcondvar_t *cvp, kmutex_t *mtx)
{
DEFINE_WAIT(wait);
int flag = 1;
BUG_ON(cvp == NULL || mtx == NULL);
BUG_ON(cvp->cv_magic != CV_MAGIC);
BUG_ON(!mutex_owned(mtx));
if (cvp->cv_mutex == NULL)
cvp->cv_mutex = mtx;
/* Ensure the same mutex is used by all callers */
BUG_ON(cvp->cv_mutex != mtx);
for (;;) {
prepare_to_wait_exclusive(&cvp->cv_event, &wait,
TASK_INTERRUPTIBLE);
/* Must occur after we are added to the list but only once */
if (flag) {
atomic_inc(&cvp->cv_waiters);
flag = 0;
}
/* XXX - The correct thing to do here may be to wake up and
* force the caller to handle the signal. Spurious wakeups
* should already be safely handled by the caller. */
if (signal_pending(current))
flush_signals(current);
/* Mutex should be dropped after prepare_to_wait() this
* ensures we're linked in to the waiters list and avoids the
* race where 'cvp->cv_waiters > 0' but the list is empty. */
mutex_exit(mtx);
schedule();
mutex_enter(mtx);
/* XXX - The correct thing to do here may be to wake up and
* force the caller to handle the signal. Spurious wakeups
* should already be safely handled by the caller. */
if (signal_pending(current))
continue;
break;
}
atomic_dec(&cvp->cv_waiters);
finish_wait(&cvp->cv_event, &wait);
}
/* 'expire_time' argument is an absolute wall clock time in jiffies.
* Return value is time left (expire_time - now) or -1 if timeout occurred.
*/
static __inline__ clock_t
cv_timedwait(kcondvar_t *cvp, kmutex_t *mtx, clock_t expire_time)
{
DEFINE_WAIT(wait);
clock_t time_left;
int flag = 1;
BUG_ON(cvp == NULL || mtx == NULL);
BUG_ON(cvp->cv_magic != CV_MAGIC);
BUG_ON(!mutex_owned(mtx));
if (cvp->cv_mutex == NULL)
cvp->cv_mutex = mtx;
/* XXX - Does not handle jiffie wrap properly */
time_left = expire_time - jiffies;
if (time_left <= 0)
return -1;
/* Ensure the same mutex is used by all callers */
BUG_ON(cvp->cv_mutex != mtx);
for (;;) {
prepare_to_wait_exclusive(&cvp->cv_event, &wait,
TASK_INTERRUPTIBLE);
if (flag) {
atomic_inc(&cvp->cv_waiters);
flag = 0;
}
/* XXX - The correct thing to do here may be to wake up and
* force the caller to handle the signal. Spurious wakeups
* should already be safely handled by the caller. */
if (signal_pending(current))
flush_signals(current);
/* Mutex should be dropped after prepare_to_wait() this
* ensures we're linked in to the waiters list and avoids the
* race where 'cvp->cv_waiters > 0' but the list is empty. */
mutex_exit(mtx);
time_left = schedule_timeout(time_left);
mutex_enter(mtx);
/* XXX - The correct thing to do here may be to wake up and
* force the caller to handle the signal. Spurious wakeups
* should already be safely handled by the caller. */
if (signal_pending(current)) {
if (time_left > 0)
continue;
flush_signals(current);
}
break;
}
atomic_dec(&cvp->cv_waiters);
finish_wait(&cvp->cv_event, &wait);
return (time_left > 0 ? time_left : -1);
}
static __inline__ void
cv_signal(kcondvar_t *cvp)
{
BUG_ON(cvp == NULL);
BUG_ON(cvp->cv_magic != CV_MAGIC);
/* All waiters are added with WQ_FLAG_EXCLUSIVE so only one
* waiter will be set runable with each call to wake_up().
* Additionally wake_up() holds a spin_lock assoicated with
* the wait queue to ensure we don't race waking up processes. */
if (atomic_read(&cvp->cv_waiters) > 0)
wake_up(&cvp->cv_event);
}
static __inline__ void
cv_broadcast(kcondvar_t *cvp)
{
BUG_ON(cvp == NULL);
BUG_ON(cvp->cv_magic != CV_MAGIC);
/* Wake_up_all() will wake up all waiters even those which
* have the WQ_FLAG_EXCLUSIVE flag set. */
if (atomic_read(&cvp->cv_waiters) > 0)
wake_up_all(&cvp->cv_event);
}
#endif /* _LINUX_CONDVAR_H */
|
