1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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 "primpl.h"
7 #include "obsolete/prsem.h"
8 
9 /************************************************************************/
10 
11 /*
12 ** Create a new semaphore.
13 */
PR_NewSem(PRUintn value)14 PR_IMPLEMENT(PRSemaphore*) PR_NewSem(PRUintn value)
15 {
16     PRSemaphore *sem;
17     PRCondVar *cvar;
18     PRLock *lock;
19 
20     sem = PR_NEWZAP(PRSemaphore);
21     if (sem) {
22 #ifdef HAVE_CVAR_BUILT_ON_SEM
23         _PR_MD_NEW_SEM(&sem->md, value);
24 #else
25         lock = PR_NewLock();
26         if (!lock) {
27             PR_DELETE(sem);
28             return NULL;
29     	}
30 
31         cvar = PR_NewCondVar(lock);
32         if (!cvar) {
33             PR_DestroyLock(lock);
34             PR_DELETE(sem);
35             return NULL;
36     	}
37     	sem->cvar = cvar;
38     	sem->count = value;
39 #endif
40     }
41     return sem;
42 }
43 
44 /*
45 ** Destroy a semaphore. There must be no thread waiting on the semaphore.
46 ** The caller is responsible for guaranteeing that the semaphore is
47 ** no longer in use.
48 */
PR_DestroySem(PRSemaphore * sem)49 PR_IMPLEMENT(void) PR_DestroySem(PRSemaphore *sem)
50 {
51 #ifdef HAVE_CVAR_BUILT_ON_SEM
52     _PR_MD_DESTROY_SEM(&sem->md);
53 #else
54     PR_ASSERT(sem->waiters == 0);
55 
56     PR_DestroyLock(sem->cvar->lock);
57     PR_DestroyCondVar(sem->cvar);
58 #endif
59     PR_DELETE(sem);
60 }
61 
62 /*
63 ** Wait on a Semaphore.
64 **
65 ** This routine allows a calling thread to wait or proceed depending upon the
66 ** state of the semahore sem. The thread can proceed only if the counter value
67 ** of the semaphore sem is currently greater than 0. If the value of semaphore
68 ** sem is positive, it is decremented by one and the routine returns immediately
69 ** allowing the calling thread to continue. If the value of semaphore sem is 0,
70 ** the calling thread blocks awaiting the semaphore to be released by another
71 ** thread.
72 **
73 ** This routine can return PR_PENDING_INTERRUPT if the waiting thread
74 ** has been interrupted.
75 */
PR_WaitSem(PRSemaphore * sem)76 PR_IMPLEMENT(PRStatus) PR_WaitSem(PRSemaphore *sem)
77 {
78 	PRStatus status = PR_SUCCESS;
79 
80 #ifdef HAVE_CVAR_BUILT_ON_SEM
81 	return _PR_MD_WAIT_SEM(&sem->md);
82 #else
83 	PR_Lock(sem->cvar->lock);
84 	while (sem->count == 0) {
85 		sem->waiters++;
86 		status = PR_WaitCondVar(sem->cvar, PR_INTERVAL_NO_TIMEOUT);
87 		sem->waiters--;
88 		if (status != PR_SUCCESS)
89 			break;
90 	}
91 	if (status == PR_SUCCESS)
92 		sem->count--;
93 	PR_Unlock(sem->cvar->lock);
94 #endif
95 
96 	return (status);
97 }
98 
99 /*
100 ** This routine increments the counter value of the semaphore. If other threads
101 ** are blocked for the semaphore, then the scheduler will determine which ONE
102 ** thread will be unblocked.
103 */
PR_PostSem(PRSemaphore * sem)104 PR_IMPLEMENT(void) PR_PostSem(PRSemaphore *sem)
105 {
106 #ifdef HAVE_CVAR_BUILT_ON_SEM
107 	_PR_MD_POST_SEM(&sem->md);
108 #else
109 	PR_Lock(sem->cvar->lock);
110 	if (sem->waiters)
111 		PR_NotifyCondVar(sem->cvar);
112 	sem->count++;
113 	PR_Unlock(sem->cvar->lock);
114 #endif
115 }
116 
117 #if DEBUG
118 /*
119 ** Returns the value of the semaphore referenced by sem without affecting
120 ** the state of the semaphore.  The value represents the semaphore vaule
121 ** at the time of the call, but may not be the actual value when the
122 ** caller inspects it. (FOR DEBUGGING ONLY)
123 */
PR_GetValueSem(PRSemaphore * sem)124 PR_IMPLEMENT(PRUintn) PR_GetValueSem(PRSemaphore *sem)
125 {
126 	PRUintn rv;
127 
128 #ifdef HAVE_CVAR_BUILT_ON_SEM
129 	rv = _PR_MD_GET_VALUE_SEM(&sem->md);
130 #else
131 	PR_Lock(sem->cvar->lock);
132 	rv = sem->count;
133 	PR_Unlock(sem->cvar->lock);
134 #endif
135 
136 	return rv;
137 }
138 #endif
139