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comparison: nsprpub/pr/src/bthreads/btmon.c

nsprpub/pr/src/bthreads/btmon.c

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1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2 /* This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
5
6 #include <kernel/OS.h>
7
8 #include "primpl.h"
9
10 /*
11 ** Create a new monitor. Monitors are re-entrant locks with a single built-in
12 ** condition variable.
13 **
14 ** This may fail if memory is tight or if some operating system resource
15 ** is low.
16 */
17 PR_IMPLEMENT(PRMonitor*)
18 PR_NewMonitor (void)
19 {
20 PRMonitor *mon;
21 PRCondVar *cvar;
22 PRLock *lock;
23
24 mon = PR_NEWZAP( PRMonitor );
25 if( mon )
26 {
27 lock = PR_NewLock();
28 if( !lock )
29 {
30 PR_DELETE( mon );
31 return( 0 );
32 }
33
34 cvar = PR_NewCondVar( lock );
35 if( !cvar )
36 {
37 PR_DestroyLock( lock );
38 PR_DELETE( mon );
39 return( 0 );
40 }
41
42 mon->cvar = cvar;
43 mon->name = NULL;
44 }
45
46 return( mon );
47 }
48
49 PR_IMPLEMENT(PRMonitor*) PR_NewNamedMonitor(const char* name)
50 {
51 PRMonitor* mon = PR_NewMonitor();
52 if( mon )
53 {
54 mon->name = name;
55 }
56 return mon;
57 }
58
59 /*
60 ** Destroy a monitor. The caller is responsible for guaranteeing that the
61 ** monitor is no longer in use. There must be no thread waiting on the
62 ** monitor's condition variable and that the lock is not held.
63 **
64 */
65 PR_IMPLEMENT(void)
66 PR_DestroyMonitor (PRMonitor *mon)
67 {
68 PR_DestroyLock( mon->cvar->lock );
69 PR_DestroyCondVar( mon->cvar );
70 PR_DELETE( mon );
71 }
72
73 /*
74 ** Enter the lock associated with the monitor. If the calling thread currently
75 ** is in the monitor, the call to enter will silently succeed. In either case,
76 ** it will increment the entry count by one.
77 */
78 PR_IMPLEMENT(void)
79 PR_EnterMonitor (PRMonitor *mon)
80 {
81 if( mon->cvar->lock->owner == find_thread( NULL ) )
82 {
83 mon->entryCount++;
84
85 } else
86 {
87 PR_Lock( mon->cvar->lock );
88 mon->entryCount = 1;
89 }
90 }
91
92 /*
93 ** Decrement the entry count associated with the monitor. If the decremented
94 ** entry count is zero, the monitor is exited. Returns PR_FAILURE if the
95 ** calling thread has not entered the monitor.
96 */
97 PR_IMPLEMENT(PRStatus)
98 PR_ExitMonitor (PRMonitor *mon)
99 {
100 if( mon->cvar->lock->owner != find_thread( NULL ) )
101 {
102 return( PR_FAILURE );
103 }
104 if( --mon->entryCount == 0 )
105 {
106 return( PR_Unlock( mon->cvar->lock ) );
107 }
108 return( PR_SUCCESS );
109 }
110
111 /*
112 ** Wait for a notify on the monitor's condition variable. Sleep for "ticks"
113 ** amount of time (if "ticks" is PR_INTERVAL_NO_TIMEOUT then the sleep is
114 ** indefinite).
115 **
116 ** While the thread is waiting it exits the monitor (as if it called
117 ** PR_ExitMonitor as many times as it had called PR_EnterMonitor). When
118 ** the wait has finished the thread regains control of the monitors lock
119 ** with the same entry count as before the wait began.
120 **
121 ** The thread waiting on the monitor will be resumed when the monitor is
122 ** notified (assuming the thread is the next in line to receive the
123 ** notify) or when the "ticks" timeout elapses.
124 **
125 ** Returns PR_FAILURE if the caller has not entered the monitor.
126 */
127 PR_IMPLEMENT(PRStatus)
128 PR_Wait (PRMonitor *mon, PRIntervalTime ticks)
129 {
130 PRUint32 entryCount;
131 PRUintn status;
132 PRThread *meThread;
133 thread_id me = find_thread( NULL );
134 meThread = PR_GetCurrentThread();
135
136 if( mon->cvar->lock->owner != me ) return( PR_FAILURE );
137
138 entryCount = mon->entryCount;
139 mon->entryCount = 0;
140
141 status = PR_WaitCondVar( mon->cvar, ticks );
142
143 mon->entryCount = entryCount;
144
145 return( status );
146 }
147
148 /*
149 ** Notify a thread waiting on the monitor's condition variable. If a thread
150 ** is waiting on the condition variable (using PR_Wait) then it is awakened
151 ** and attempts to reenter the monitor.
152 */
153 PR_IMPLEMENT(PRStatus)
154 PR_Notify (PRMonitor *mon)
155 {
156 if( mon->cvar->lock->owner != find_thread( NULL ) )
157 {
158 return( PR_FAILURE );
159 }
160
161 PR_NotifyCondVar( mon->cvar );
162 return( PR_SUCCESS );
163 }
164
165 /*
166 ** Notify all of the threads waiting on the monitor's condition variable.
167 ** All of threads waiting on the condition are scheduled to reenter the
168 ** monitor.
169 */
170 PR_IMPLEMENT(PRStatus)
171 PR_NotifyAll (PRMonitor *mon)
172 {
173 if( mon->cvar->lock->owner != find_thread( NULL ) )
174 {
175 return( PR_FAILURE );
176 }
177
178 PR_NotifyAllCondVar( mon->cvar );
179 return( PR_SUCCESS );
180 }
181
182 /*
183 ** Return the number of times that the current thread has entered the
184 ** lock. Returns zero if the current thread has not entered the lock.
185 */
186 PR_IMPLEMENT(PRIntn)
187 PR_GetMonitorEntryCount(PRMonitor *mon)
188 {
189 return( (mon->cvar->lock->owner == find_thread( NULL )) ?
190 mon->entryCount : 0 );
191 }
192
193 /*
194 ** If the current thread is in |mon|, this assertion is guaranteed to
195 ** succeed. Otherwise, the behavior of this function is undefined.
196 */
197 PR_IMPLEMENT(void)
198 PR_AssertCurrentThreadInMonitor(PRMonitor *mon)
199 {
200 PR_ASSERT_CURRENT_THREAD_OWNS_LOCK(mon->cvar->lock);
201 }

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