/src/nspr/pr/src/misc/pratom.c

Source
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
**     PR Atomic operations
*/

#include "pratom.h"
#include "primpl.h"

#include <string.h>

/*
 * The following is a fallback implementation that emulates
 * atomic operations for platforms without atomic operations.
 * If a platform has atomic operations, it should define the
 * macro _PR_HAVE_ATOMIC_OPS, and the following will not be
 * compiled in.
 */

#if !defined(_PR_HAVE_ATOMIC_OPS)

#  if defined(_PR_PTHREADS)
/*
 * PR_AtomicDecrement() is used in NSPR's thread-specific data
 * destructor.  Because thread-specific data destructors may be
 * invoked after a PR_Cleanup() call, we need an implementation
 * of the atomic routines that doesn't need NSPR to be initialized.
 */

/*
 * We use a set of locks for all the emulated atomic operations.
 * By hashing on the address of the integer to be locked the
 * contention between multiple threads should be lessened.
 *
 * The number of atomic locks can be set by the environment variable
 * NSPR_ATOMIC_HASH_LOCKS
 */

/*
 * lock counts should be a power of 2
 */
#    define DEFAULT_ATOMIC_LOCKS                              \
      16 /* should be in sync with the number of initializers \
             below */
#    define MAX_ATOMIC_LOCKS (4 * 1024)

static pthread_mutex_t static_atomic_locks[DEFAULT_ATOMIC_LOCKS] = {
    PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
    PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
    PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
    PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
    PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
    PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
    PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
    PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER};

#    ifdef DEBUG
static PRInt32 static_hash_lock_counts[DEFAULT_ATOMIC_LOCKS];
static PRInt32* hash_lock_counts = static_hash_lock_counts;
#    endif

static PRUint32 num_atomic_locks = DEFAULT_ATOMIC_LOCKS;
static pthread_mutex_t* atomic_locks = static_atomic_locks;
static PRUint32 atomic_hash_mask = DEFAULT_ATOMIC_LOCKS - 1;

#    define _PR_HASH_FOR_LOCK(ptr)                                       \
      ((PRUint32)(((PRUptrdiff)(ptr) >> 2) ^ ((PRUptrdiff)(ptr) >> 8)) & \
       atomic_hash_mask)

void _PR_MD_INIT_ATOMIC() {
  char* eval;
  int index;

  PR_ASSERT(PR_FloorLog2(MAX_ATOMIC_LOCKS) == PR_CeilingLog2(MAX_ATOMIC_LOCKS));

  PR_ASSERT(PR_FloorLog2(DEFAULT_ATOMIC_LOCKS) ==
            PR_CeilingLog2(DEFAULT_ATOMIC_LOCKS));

  if (((eval = getenv("NSPR_ATOMIC_HASH_LOCKS")) != NULL) &&
      ((num_atomic_locks = atoi(eval)) != DEFAULT_ATOMIC_LOCKS)) {
    if (num_atomic_locks > MAX_ATOMIC_LOCKS) {
      num_atomic_locks = MAX_ATOMIC_LOCKS;
    } else if (num_atomic_locks < 1) {
      num_atomic_locks = 1;
    } else {
      num_atomic_locks = PR_FloorLog2(num_atomic_locks);
      num_atomic_locks = 1L << num_atomic_locks;
    }
    atomic_locks =
        (pthread_mutex_t*)PR_Malloc(sizeof(pthread_mutex_t) * num_atomic_locks);
    if (atomic_locks) {
      for (index = 0; index < num_atomic_locks; index++) {
        if (pthread_mutex_init(&atomic_locks[index], NULL)) {
          PR_DELETE(atomic_locks);
          atomic_locks = NULL;
          break;
        }
      }
    }
#    ifdef DEBUG
    if (atomic_locks) {
      hash_lock_counts = PR_CALLOC(num_atomic_locks * sizeof(PRInt32));
      if (hash_lock_counts == NULL) {
        PR_DELETE(atomic_locks);
        atomic_locks = NULL;
      }
    }
#    endif
    if (atomic_locks == NULL) {
      /*
       *  Use statically allocated locks
       */
      atomic_locks = static_atomic_locks;
      num_atomic_locks = DEFAULT_ATOMIC_LOCKS;
#    ifdef DEBUG
      hash_lock_counts = static_hash_lock_counts;
#    endif
    }
    atomic_hash_mask = num_atomic_locks - 1;
  }
  PR_ASSERT(PR_FloorLog2(num_atomic_locks) == PR_CeilingLog2(num_atomic_locks));
}

PRInt32 _PR_MD_ATOMIC_INCREMENT(PRInt32* val) {
  PRInt32 rv;
  PRInt32 idx = _PR_HASH_FOR_LOCK(val);

  pthread_mutex_lock(&atomic_locks[idx]);
  rv = ++(*val);
#    ifdef DEBUG
  hash_lock_counts[idx]++;
#    endif
  pthread_mutex_unlock(&atomic_locks[idx]);
  return rv;
}

PRInt32 _PR_MD_ATOMIC_ADD(PRInt32* ptr, PRInt32 val) {
  PRInt32 rv;
  PRInt32 idx = _PR_HASH_FOR_LOCK(ptr);

  pthread_mutex_lock(&atomic_locks[idx]);
  rv = ((*ptr) += val);
#    ifdef DEBUG
  hash_lock_counts[idx]++;
#    endif
  pthread_mutex_unlock(&atomic_locks[idx]);
  return rv;
}

PRInt32 _PR_MD_ATOMIC_DECREMENT(PRInt32* val) {
  PRInt32 rv;
  PRInt32 idx = _PR_HASH_FOR_LOCK(val);

  pthread_mutex_lock(&atomic_locks[idx]);
  rv = --(*val);
#    ifdef DEBUG
  hash_lock_counts[idx]++;
#    endif
  pthread_mutex_unlock(&atomic_locks[idx]);
  return rv;
}

PRInt32 _PR_MD_ATOMIC_SET(PRInt32* val, PRInt32 newval) {
  PRInt32 rv;
  PRInt32 idx = _PR_HASH_FOR_LOCK(val);

  pthread_mutex_lock(&atomic_locks[idx]);
  rv = *val;
  *val = newval;
#    ifdef DEBUG
  hash_lock_counts[idx]++;
#    endif
  pthread_mutex_unlock(&atomic_locks[idx]);
  return rv;
}
#  else  /* _PR_PTHREADS */
/*
 * We use a single lock for all the emulated atomic operations.
 * The lock contention should be acceptable.
 */
static PRLock* atomic_lock = NULL;
void _PR_MD_INIT_ATOMIC(void) {
  if (atomic_lock == NULL) {
    atomic_lock = PR_NewLock();
  }
}

PRInt32 _PR_MD_ATOMIC_INCREMENT(PRInt32* val) {
  PRInt32 rv;

  if (!_pr_initialized) {
    _PR_ImplicitInitialization();
  }
  PR_Lock(atomic_lock);
  rv = ++(*val);
  PR_Unlock(atomic_lock);
  return rv;
}

PRInt32 _PR_MD_ATOMIC_ADD(PRInt32* ptr, PRInt32 val) {
  PRInt32 rv;

  if (!_pr_initialized) {
    _PR_ImplicitInitialization();
  }
  PR_Lock(atomic_lock);
  rv = ((*ptr) += val);
  PR_Unlock(atomic_lock);
  return rv;
}

PRInt32 _PR_MD_ATOMIC_DECREMENT(PRInt32* val) {
  PRInt32 rv;

  if (!_pr_initialized) {
    _PR_ImplicitInitialization();
  }
  PR_Lock(atomic_lock);
  rv = --(*val);
  PR_Unlock(atomic_lock);
  return rv;
}

PRInt32 _PR_MD_ATOMIC_SET(PRInt32* val, PRInt32 newval) {
  PRInt32 rv;

  if (!_pr_initialized) {
    _PR_ImplicitInitialization();
  }
  PR_Lock(atomic_lock);
  rv = *val;
  *val = newval;
  PR_Unlock(atomic_lock);
  return rv;
}
#  endif /* _PR_PTHREADS */

#endif /* !_PR_HAVE_ATOMIC_OPS */

void _PR_InitAtomic(void) { _PR_MD_INIT_ATOMIC(); }

PR_IMPLEMENT(PRInt32)
PR_AtomicIncrement(PRInt32* val) { return _PR_MD_ATOMIC_INCREMENT(val); }

PR_IMPLEMENT(PRInt32)
PR_AtomicDecrement(PRInt32* val) { return _PR_MD_ATOMIC_DECREMENT(val); }

PR_IMPLEMENT(PRInt32)
PR_AtomicSet(PRInt32* val, PRInt32 newval) {
  return _PR_MD_ATOMIC_SET(val, newval);
}

PR_IMPLEMENT(PRInt32)
PR_AtomicAdd(PRInt32* ptr, PRInt32 val) { return _PR_MD_ATOMIC_ADD(ptr, val); }
/*
 * For platforms, which don't support the CAS (compare-and-swap) instruction
 * (or an equivalent), the stack operations are implemented by use of PRLock
 */

PR_IMPLEMENT(PRStack*)
PR_CreateStack(const char* stack_name) {
  PRStack* stack;

  if (!_pr_initialized) {
    _PR_ImplicitInitialization();
  }

  if ((stack = PR_NEW(PRStack)) == NULL) {
    return NULL;
  }
  if (stack_name) {
    stack->prstk_name = (char*)PR_Malloc(strlen(stack_name) + 1);
    if (stack->prstk_name == NULL) {
      PR_DELETE(stack);
      return NULL;
    }
    strcpy(stack->prstk_name, stack_name);
  } else {
    stack->prstk_name = NULL;
  }

#ifndef _PR_HAVE_ATOMIC_CAS
  stack->prstk_lock = PR_NewLock();
  if (stack->prstk_lock == NULL) {
    PR_Free(stack->prstk_name);
    PR_DELETE(stack);
    return NULL;
  }
#endif /* !_PR_HAVE_ATOMIC_CAS */

  stack->prstk_head.prstk_elem_next = NULL;

  return stack;
}

PR_IMPLEMENT(PRStatus)
PR_DestroyStack(PRStack* stack) {
  if (stack->prstk_head.prstk_elem_next != NULL) {
    PR_SetError(PR_INVALID_STATE_ERROR, 0);
    return PR_FAILURE;
  }

  if (stack->prstk_name) {
    PR_Free(stack->prstk_name);
  }
#ifndef _PR_HAVE_ATOMIC_CAS
  PR_DestroyLock(stack->prstk_lock);
#endif /* !_PR_HAVE_ATOMIC_CAS */
  PR_DELETE(stack);

  return PR_SUCCESS;
}

#ifndef _PR_HAVE_ATOMIC_CAS

PR_IMPLEMENT(void)
PR_StackPush(PRStack* stack, PRStackElem* stack_elem) {
  PR_Lock(stack->prstk_lock);
  stack_elem->prstk_elem_next = stack->prstk_head.prstk_elem_next;
  stack->prstk_head.prstk_elem_next = stack_elem;
  PR_Unlock(stack->prstk_lock);
  return;
}

PR_IMPLEMENT(PRStackElem*)
PR_StackPop(PRStack* stack) {
  PRStackElem* element;

  PR_Lock(stack->prstk_lock);
  element = stack->prstk_head.prstk_elem_next;
  if (element != NULL) {
    stack->prstk_head.prstk_elem_next = element->prstk_elem_next;
    element->prstk_elem_next = NULL; /* debugging aid */
  }
  PR_Unlock(stack->prstk_lock);
  return element;
}
#endif /* !_PR_HAVE_ATOMIC_CAS */

Coverage Report

Created: 2026-08-18 06:34

Line	Count	Source
1		/* This Source Code Form is subject to the terms of the Mozilla Public
2		* License, v. 2.0. If a copy of the MPL was not distributed with this
3		* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
4
5		/*
6		** PR Atomic operations
7		*/
8
9		#include "pratom.h"
10		#include "primpl.h"
11
12		#include <string.h>
13
14		/*
15		* The following is a fallback implementation that emulates
16		* atomic operations for platforms without atomic operations.
17		* If a platform has atomic operations, it should define the
18		* macro _PR_HAVE_ATOMIC_OPS, and the following will not be
19		* compiled in.
20		*/
21
22		#if !defined(_PR_HAVE_ATOMIC_OPS)
23
24		# if defined(_PR_PTHREADS)
25		/*
26		* PR_AtomicDecrement() is used in NSPR's thread-specific data
27		* destructor. Because thread-specific data destructors may be
28		* invoked after a PR_Cleanup() call, we need an implementation
29		* of the atomic routines that doesn't need NSPR to be initialized.
30		*/
31
32		/*
33		* We use a set of locks for all the emulated atomic operations.
34		* By hashing on the address of the integer to be locked the
35		* contention between multiple threads should be lessened.
36		*
37		* The number of atomic locks can be set by the environment variable
38		* NSPR_ATOMIC_HASH_LOCKS
39		*/
40
41		/*
42		* lock counts should be a power of 2
43		*/
44		# define DEFAULT_ATOMIC_LOCKS \
45		16 /* should be in sync with the number of initializers \
46		below */
47		# define MAX_ATOMIC_LOCKS (4 * 1024)
48
49		static pthread_mutex_t static_atomic_locks[DEFAULT_ATOMIC_LOCKS] = {
50		PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
51		PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
52		PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
53		PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
54		PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
55		PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
56		PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
57		PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER};
58
59		# ifdef DEBUG
60		static PRInt32 static_hash_lock_counts[DEFAULT_ATOMIC_LOCKS];
61		static PRInt32* hash_lock_counts = static_hash_lock_counts;
62		# endif
63
64		static PRUint32 num_atomic_locks = DEFAULT_ATOMIC_LOCKS;
65		static pthread_mutex_t* atomic_locks = static_atomic_locks;
66		static PRUint32 atomic_hash_mask = DEFAULT_ATOMIC_LOCKS - 1;
67
68		# define _PR_HASH_FOR_LOCK(ptr) \
69		((PRUint32)(((PRUptrdiff)(ptr) >> 2) ^ ((PRUptrdiff)(ptr) >> 8)) & \
70		atomic_hash_mask)
71
72		void _PR_MD_INIT_ATOMIC() {
73		char* eval;
74		int index;
75
76		PR_ASSERT(PR_FloorLog2(MAX_ATOMIC_LOCKS) == PR_CeilingLog2(MAX_ATOMIC_LOCKS));
77
78		PR_ASSERT(PR_FloorLog2(DEFAULT_ATOMIC_LOCKS) ==
79		PR_CeilingLog2(DEFAULT_ATOMIC_LOCKS));
80
81		if (((eval = getenv("NSPR_ATOMIC_HASH_LOCKS")) != NULL) &&
82		((num_atomic_locks = atoi(eval)) != DEFAULT_ATOMIC_LOCKS)) {
83		if (num_atomic_locks > MAX_ATOMIC_LOCKS) {
84		num_atomic_locks = MAX_ATOMIC_LOCKS;
85		} else if (num_atomic_locks < 1) {
86		num_atomic_locks = 1;
87		} else {
88		num_atomic_locks = PR_FloorLog2(num_atomic_locks);
89		num_atomic_locks = 1L << num_atomic_locks;
90		}
91		atomic_locks =
92		(pthread_mutex_t)PR_Malloc(sizeof(pthread_mutex_t) num_atomic_locks);
93		if (atomic_locks) {
94		for (index = 0; index < num_atomic_locks; index++) {
95		if (pthread_mutex_init(&atomic_locks[index], NULL)) {
96		PR_DELETE(atomic_locks);
97		atomic_locks = NULL;
98		break;
99		}
100		}
101		}
102		# ifdef DEBUG
103		if (atomic_locks) {
104		hash_lock_counts = PR_CALLOC(num_atomic_locks * sizeof(PRInt32));
105		if (hash_lock_counts == NULL) {
106		PR_DELETE(atomic_locks);
107		atomic_locks = NULL;
108		}
109		}
110		# endif
111		if (atomic_locks == NULL) {
112		/*
113		* Use statically allocated locks
114		*/
115		atomic_locks = static_atomic_locks;
116		num_atomic_locks = DEFAULT_ATOMIC_LOCKS;
117		# ifdef DEBUG
118		hash_lock_counts = static_hash_lock_counts;
119		# endif
120		}
121		atomic_hash_mask = num_atomic_locks - 1;
122		}
123		PR_ASSERT(PR_FloorLog2(num_atomic_locks) == PR_CeilingLog2(num_atomic_locks));
124		}
125
126		PRInt32 _PR_MD_ATOMIC_INCREMENT(PRInt32* val) {
127		PRInt32 rv;
128		PRInt32 idx = _PR_HASH_FOR_LOCK(val);
129
130		pthread_mutex_lock(&atomic_locks[idx]);
131		rv = ++(*val);
132		# ifdef DEBUG
133		hash_lock_counts[idx]++;
134		# endif
135		pthread_mutex_unlock(&atomic_locks[idx]);
136		return rv;
137		}
138
139		PRInt32 _PR_MD_ATOMIC_ADD(PRInt32* ptr, PRInt32 val) {
140		PRInt32 rv;
141		PRInt32 idx = _PR_HASH_FOR_LOCK(ptr);
142
143		pthread_mutex_lock(&atomic_locks[idx]);
144		rv = ((*ptr) += val);
145		# ifdef DEBUG
146		hash_lock_counts[idx]++;
147		# endif
148		pthread_mutex_unlock(&atomic_locks[idx]);
149		return rv;
150		}
151
152		PRInt32 _PR_MD_ATOMIC_DECREMENT(PRInt32* val) {
153		PRInt32 rv;
154		PRInt32 idx = _PR_HASH_FOR_LOCK(val);
155
156		pthread_mutex_lock(&atomic_locks[idx]);
157		rv = --(*val);
158		# ifdef DEBUG
159		hash_lock_counts[idx]++;
160		# endif
161		pthread_mutex_unlock(&atomic_locks[idx]);
162		return rv;
163		}
164
165		PRInt32 _PR_MD_ATOMIC_SET(PRInt32* val, PRInt32 newval) {
166		PRInt32 rv;
167		PRInt32 idx = _PR_HASH_FOR_LOCK(val);
168
169		pthread_mutex_lock(&atomic_locks[idx]);
170		rv = *val;
171		*val = newval;
172		# ifdef DEBUG
173		hash_lock_counts[idx]++;
174		# endif
175		pthread_mutex_unlock(&atomic_locks[idx]);
176		return rv;
177		}
178		# else /* _PR_PTHREADS */
179		/*
180		* We use a single lock for all the emulated atomic operations.
181		* The lock contention should be acceptable.
182		*/
183		static PRLock* atomic_lock = NULL;
184		void _PR_MD_INIT_ATOMIC(void) {
185		if (atomic_lock == NULL) {
186		atomic_lock = PR_NewLock();
187		}
188		}
189
190		PRInt32 _PR_MD_ATOMIC_INCREMENT(PRInt32* val) {
191		PRInt32 rv;
192
193		if (!_pr_initialized) {
194		_PR_ImplicitInitialization();
195		}
196		PR_Lock(atomic_lock);
197		rv = ++(*val);
198		PR_Unlock(atomic_lock);
199		return rv;
200		}
201
202		PRInt32 _PR_MD_ATOMIC_ADD(PRInt32* ptr, PRInt32 val) {
203		PRInt32 rv;
204
205		if (!_pr_initialized) {
206		_PR_ImplicitInitialization();
207		}
208		PR_Lock(atomic_lock);
209		rv = ((*ptr) += val);
210		PR_Unlock(atomic_lock);
211		return rv;
212		}
213
214		PRInt32 _PR_MD_ATOMIC_DECREMENT(PRInt32* val) {
215		PRInt32 rv;
216
217		if (!_pr_initialized) {
218		_PR_ImplicitInitialization();
219		}
220		PR_Lock(atomic_lock);
221		rv = --(*val);
222		PR_Unlock(atomic_lock);
223		return rv;
224		}
225
226		PRInt32 _PR_MD_ATOMIC_SET(PRInt32* val, PRInt32 newval) {
227		PRInt32 rv;
228
229		if (!_pr_initialized) {
230		_PR_ImplicitInitialization();
231		}
232		PR_Lock(atomic_lock);
233		rv = *val;
234		*val = newval;
235		PR_Unlock(atomic_lock);
236		return rv;
237		}
238		# endif /* _PR_PTHREADS */
239
240		#endif /* !_PR_HAVE_ATOMIC_OPS */
241
242	19	void _PR_InitAtomic(void) { _PR_MD_INIT_ATOMIC(); }
243
244		PR_IMPLEMENT(PRInt32)
245	0	PR_AtomicIncrement(PRInt32* val) { return _PR_MD_ATOMIC_INCREMENT(val); }
246
247		PR_IMPLEMENT(PRInt32)
248	0	PR_AtomicDecrement(PRInt32* val) { return _PR_MD_ATOMIC_DECREMENT(val); }
249
250		PR_IMPLEMENT(PRInt32)
251	0	PR_AtomicSet(PRInt32* val, PRInt32 newval) {
252	0	return _PR_MD_ATOMIC_SET(val, newval);
253	0	}
254
255		PR_IMPLEMENT(PRInt32)
256	0	PR_AtomicAdd(PRInt32* ptr, PRInt32 val) { return _PR_MD_ATOMIC_ADD(ptr, val); }
257		/*
258		* For platforms, which don't support the CAS (compare-and-swap) instruction
259		* (or an equivalent), the stack operations are implemented by use of PRLock
260		*/
261
262		PR_IMPLEMENT(PRStack*)
263	0	PR_CreateStack(const char* stack_name) {
264	0	PRStack* stack;
265
266	0	if (!_pr_initialized) {
267	0	_PR_ImplicitInitialization();
268	0	}
269
270	0	if ((stack = PR_NEW(PRStack)) == NULL) {
271	0	return NULL;
272	0	}
273	0	if (stack_name) {
274	0	stack->prstk_name = (char*)PR_Malloc(strlen(stack_name) + 1);
275	0	if (stack->prstk_name == NULL) {
276	0	PR_DELETE(stack);
277	0	return NULL;
278	0	}
279	0	strcpy(stack->prstk_name, stack_name);
280	0	} else {
281	0	stack->prstk_name = NULL;
282	0	}
283
284	0	#ifndef _PR_HAVE_ATOMIC_CAS
285	0	stack->prstk_lock = PR_NewLock();
286	0	if (stack->prstk_lock == NULL) {
287	0	PR_Free(stack->prstk_name);
288	0	PR_DELETE(stack);
289	0	return NULL;
290	0	}
291	0	#endif /* !_PR_HAVE_ATOMIC_CAS */
292
293	0	stack->prstk_head.prstk_elem_next = NULL;
294
295	0	return stack;
296	0	}
297
298		PR_IMPLEMENT(PRStatus)
299	0	PR_DestroyStack(PRStack* stack) {
300	0	if (stack->prstk_head.prstk_elem_next != NULL) {
301	0	PR_SetError(PR_INVALID_STATE_ERROR, 0);
302	0	return PR_FAILURE;
303	0	}
304
305	0	if (stack->prstk_name) {
306	0	PR_Free(stack->prstk_name);
307	0	}
308	0	#ifndef _PR_HAVE_ATOMIC_CAS
309	0	PR_DestroyLock(stack->prstk_lock);
310	0	#endif /* !_PR_HAVE_ATOMIC_CAS */
311	0	PR_DELETE(stack);
312
313	0	return PR_SUCCESS;
314	0	}
315
316		#ifndef _PR_HAVE_ATOMIC_CAS
317
318		PR_IMPLEMENT(void)
319	0	PR_StackPush(PRStack* stack, PRStackElem* stack_elem) {
320	0	PR_Lock(stack->prstk_lock);
321	0	stack_elem->prstk_elem_next = stack->prstk_head.prstk_elem_next;
322	0	stack->prstk_head.prstk_elem_next = stack_elem;
323	0	PR_Unlock(stack->prstk_lock);
324	0	return;
325	0	}
326
327		PR_IMPLEMENT(PRStackElem*)
328	0	PR_StackPop(PRStack* stack) {
329	0	PRStackElem* element;
330
331	0	PR_Lock(stack->prstk_lock);
332	0	element = stack->prstk_head.prstk_elem_next;
333	0	if (element != NULL) {
334	0	stack->prstk_head.prstk_elem_next = element->prstk_elem_next;
335		element->prstk_elem_next = NULL; /* debugging aid */
336	0	}
337	0	PR_Unlock(stack->prstk_lock);
338	0	return element;
339	0	}
340		#endif /* !_PR_HAVE_ATOMIC_CAS */