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Side by Side Diff: nspr/pr/src/threads/prsem.c

Issue 2078763002: Delete bundled copy of NSS and replace with README. (Closed) Base URL: https://chromium.googlesource.com/chromium/deps/nss@master
Patch Set: Delete bundled copy of NSS and replace with README. Created 4 years, 6 months ago
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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 */
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 */
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 */
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 */
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 */
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
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