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
|
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* The contents of this file are subject to the Mozilla Public
* License Version 1.1 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
*
* The Original Code is the Netscape Portable Runtime (NSPR).
*
* The Initial Developer of the Original Code is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998-2000 Netscape Communications Corporation. All
* Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the
* terms of the GNU General Public License Version 2 or later (the
* "GPL"), in which case the provisions of the GPL are applicable
* instead of those above. If you wish to allow use of your
* version of this file only under the terms of the GPL and not to
* allow others to use your version of this file under the MPL,
* indicate your decision by deleting the provisions above and
* replace them with the notice and other provisions required by
* the GPL. If you do not delete the provisions above, a recipient
* may use your version of this file under either the MPL or the
* GPL.
*/
#include <kernel/OS.h>
#include "primpl.h"
/*
** Create a new condition variable.
**
** "lock" is the lock used to protect the condition variable.
**
** Condition variables are synchronization objects that threads can use
** to wait for some condition to occur.
**
** This may fail if memory is tight or if some operating system resource
** is low. In such cases, a NULL will be returned.
*/
PR_IMPLEMENT(PRCondVar*)
PR_NewCondVar (PRLock *lock)
{
PRCondVar *cv = PR_NEW( PRCondVar );
PR_ASSERT( NULL != lock );
if( NULL != cv )
{
cv->lock = lock;
cv->isem = create_sem( 1, "nspr_sem");
PR_ASSERT( cv->isem >= B_NO_ERROR );
}
return cv;
} /* PR_NewCondVar */
/*
** Destroy a condition variable. There must be no thread
** waiting on the condvar. The caller is responsible for guaranteeing
** that the condvar is no longer in use.
**
*/
PR_IMPLEMENT(void)
PR_DestroyCondVar (PRCondVar *cvar)
{
status_t result;
result = delete_sem( cvar->isem );
PR_ASSERT( result == B_NO_ERROR );
PR_DELETE( cvar );
}
/*
** The thread that waits on a condition is blocked in a "waiting on
** condition" state until another thread notifies the condition or a
** caller specified amount of time expires. The lock associated with
** the condition variable will be released, which must have be held
** prior to the call to wait.
**
** Logically a notified thread is moved from the "waiting on condition"
** state and made "ready." When scheduled, it will attempt to reacquire
** the lock that it held when wait was called.
**
** The timeout has two well known values, PR_INTERVAL_NO_TIMEOUT and
** PR_INTERVAL_NO_WAIT. The former value requires that a condition be
** notified (or the thread interrupted) before it will resume from the
** wait. If the timeout has a value of PR_INTERVAL_NO_WAIT, the effect
** is to release the lock, possibly causing a rescheduling within the
** runtime, then immediately attempting to reacquire the lock and resume.
**
** Any other value for timeout will cause the thread to be rescheduled
** either due to explicit notification or an expired interval. The latter
** must be determined by treating time as one part of the monitored data
** being protected by the lock and tested explicitly for an expired
** interval.
**
** Returns PR_FAILURE if the caller has not locked the lock associated
** with the condition variable or the thread was interrupted (PR_Interrupt()).
** The particular reason can be extracted with PR_GetError().
*/
PR_IMPLEMENT(PRStatus)
PR_WaitCondVar (PRCondVar *cvar, PRIntervalTime timeout)
{
status_t result;
bigtime_t interval;
PR_Unlock( cvar->lock );
switch (timeout) {
case PR_INTERVAL_NO_WAIT:
/* nothing to do */
break;
case PR_INTERVAL_NO_TIMEOUT:
/* wait as long as necessary */
if( acquire_sem( cvar->isem ) != B_NO_ERROR ) return PR_FAILURE;
break;
default:
interval = (bigtime_t)PR_IntervalToMicroseconds(timeout);
/*
** in R5, this problem seems to have been resolved, so we
** won't bother with it
*/
#if !defined(B_BEOS_VERSION_5) || (B_BEOS_VERSION < B_BEOS_VERSION_5)
/*
** This is an entirely stupid bug, but... If you call
** acquire_sem_etc with a timeout of exactly 1,000,000 microseconds
** it returns immediately with B_NO_ERROR. 1,000,010 microseconds
** returns as expected. Running BeOS/Intel R3.1 at this time.
** Forwarded to Be, Inc. for resolution, Bug ID 980624-225956
**
** Update: Be couldn't reproduce it, but removing timeout++ still
** exhibits the problem on BeOS/Intel R4 and BeOS/PPC R4.
*/
if (interval == 1000000)
interval = 1000010;
#endif /* !defined(B_BEOS_VERSION_5) || (B_BEOS_VERSION < B_BEOS_VERSION_5) */
result = acquire_sem_etc( cvar->isem, 1, B_RELATIVE_TIMEOUT, interval);
if( result != B_NO_ERROR && result != B_TIMED_OUT )
return PR_FAILURE;
break;
}
PR_Lock( cvar->lock );
return PR_SUCCESS;
}
/*
** Notify ONE thread that is currently waiting on 'cvar'. Which thread is
** dependent on the implementation of the runtime. Common sense would dictate
** that all threads waiting on a single condition have identical semantics,
** therefore which one gets notified is not significant.
**
** The calling thead must hold the lock that protects the condition, as
** well as the invariants that are tightly bound to the condition, when
** notify is called.
**
** Returns PR_FAILURE if the caller has not locked the lock associated
** with the condition variable.
*/
PR_IMPLEMENT(PRStatus)
PR_NotifyCondVar (PRCondVar *cvar)
{
if( release_sem( cvar->isem ) != B_NO_ERROR ) return PR_FAILURE;
return PR_SUCCESS;
}
/*
** Notify all of the threads waiting on the condition variable. The order
** that the threads are notified is indeterminant. The lock that protects
** the condition must be held.
**
** Returns PR_FAILURE if the caller has not locked the lock associated
** with the condition variable.
*/
PR_IMPLEMENT(PRStatus)
PR_NotifyAllCondVar (PRCondVar *cvar)
{
sem_info semInfo;
if( get_sem_info( cvar->isem, &semInfo ) != B_NO_ERROR )
return PR_FAILURE;
if( release_sem_etc( cvar->isem, semInfo.count, 0 ) != B_NO_ERROR )
return PR_FAILURE;
return PR_SUCCESS;
}
|
