This file is indexed.

/usr/include/urcu/static/wfstack.h is in liburcu-dev 0.9.1-3.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  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
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
#ifndef _URCU_STATIC_WFSTACK_H
#define _URCU_STATIC_WFSTACK_H

/*
 * urcu/static/wfstack.h
 *
 * Userspace RCU library - Stack with with wait-free push, blocking traversal.
 *
 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu/wfstack.h for
 * linking dynamically with the userspace rcu library.
 *
 * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <pthread.h>
#include <assert.h>
#include <poll.h>
#include <stdbool.h>
#include <urcu/compiler.h>
#include <urcu/uatomic.h>

#ifdef __cplusplus
extern "C" {
#endif

#define CDS_WFS_END			((void *) 0x1UL)
#define CDS_WFS_ADAPT_ATTEMPTS		10	/* Retry if being set */
#define CDS_WFS_WAIT			10	/* Wait 10 ms if being set */

/*
 * Stack with wait-free push, blocking traversal.
 *
 * Stack implementing push, pop, pop_all operations, as well as iterator
 * on the stack head returned by pop_all.
 *
 * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty,
 *                       cds_wfs_first.
 * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next,
 *                      iteration on stack head returned by pop_all.
 *
 * Synchronization table:
 *
 * External synchronization techniques described in the API below is
 * required between pairs marked with "X". No external synchronization
 * required between pairs marked with "-".
 *
 *                      cds_wfs_push  __cds_wfs_pop  __cds_wfs_pop_all
 * cds_wfs_push               -              -                  -
 * __cds_wfs_pop              -              X                  X
 * __cds_wfs_pop_all          -              X                  -
 *
 * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide
 * synchronization.
 */

/*
 * cds_wfs_node_init: initialize wait-free stack node.
 */
static inline
void _cds_wfs_node_init(struct cds_wfs_node *node)
{
	node->next = NULL;
}

/*
 * __cds_wfs_init: initialize wait-free stack.
 */
static inline void ___cds_wfs_init(struct __cds_wfs_stack *s)
{
	s->head = CDS_WFS_END;
}

/*
 * cds_wfs_init: initialize wait-free stack.
 */
static inline
void _cds_wfs_init(struct cds_wfs_stack *s)
{
	int ret;

	s->head = CDS_WFS_END;
	ret = pthread_mutex_init(&s->lock, NULL);
	assert(!ret);
}

static inline bool ___cds_wfs_end(void *node)
{
	return node == CDS_WFS_END;
}

/*
 * cds_wfs_empty: return whether wait-free stack is empty.
 *
 * No memory barrier is issued. No mutual exclusion is required.
 */
static inline bool _cds_wfs_empty(cds_wfs_stack_ptr_t u_stack)
{
	struct __cds_wfs_stack *s = u_stack._s;

	return ___cds_wfs_end(CMM_LOAD_SHARED(s->head));
}

/*
 * cds_wfs_push: push a node into the stack.
 *
 * Issues a full memory barrier before push. No mutual exclusion is
 * required.
 *
 * Returns 0 if the stack was empty prior to adding the node.
 * Returns non-zero otherwise.
 */
static inline
int _cds_wfs_push(cds_wfs_stack_ptr_t u_stack, struct cds_wfs_node *node)
{
	struct __cds_wfs_stack *s = u_stack._s;
	struct cds_wfs_head *old_head, *new_head;

	assert(node->next == NULL);
	new_head = caa_container_of(node, struct cds_wfs_head, node);
	/*
	 * uatomic_xchg() implicit memory barrier orders earlier stores
	 * to node (setting it to NULL) before publication.
	 */
	old_head = uatomic_xchg(&s->head, new_head);
	/*
	 * At this point, dequeuers see a NULL node->next, they should
	 * busy-wait until node->next is set to old_head.
	 */
	CMM_STORE_SHARED(node->next, &old_head->node);
	return !___cds_wfs_end(old_head);
}

/*
 * Waiting for push to complete enqueue and return the next node.
 */
static inline struct cds_wfs_node *
___cds_wfs_node_sync_next(struct cds_wfs_node *node, int blocking)
{
	struct cds_wfs_node *next;
	int attempt = 0;

	/*
	 * Adaptative busy-looping waiting for push to complete.
	 */
	while ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
		if (!blocking)
			return CDS_WFS_WOULDBLOCK;
		if (++attempt >= CDS_WFS_ADAPT_ATTEMPTS) {
			(void) poll(NULL, 0, CDS_WFS_WAIT);	/* Wait for 10ms */
			attempt = 0;
		} else {
			caa_cpu_relax();
		}
	}

	return next;
}

static inline
struct cds_wfs_node *
___cds_wfs_pop(cds_wfs_stack_ptr_t u_stack, int *state, int blocking)
{
	struct cds_wfs_head *head, *new_head;
	struct cds_wfs_node *next;
	struct __cds_wfs_stack *s = u_stack._s;

	if (state)
		*state = 0;
	for (;;) {
		head = CMM_LOAD_SHARED(s->head);
		if (___cds_wfs_end(head)) {
			return NULL;
		}
		next = ___cds_wfs_node_sync_next(&head->node, blocking);
		if (!blocking && next == CDS_WFS_WOULDBLOCK) {
			return CDS_WFS_WOULDBLOCK;
		}
		new_head = caa_container_of(next, struct cds_wfs_head, node);
		if (uatomic_cmpxchg(&s->head, head, new_head) == head) {
			if (state && ___cds_wfs_end(new_head))
				*state |= CDS_WFS_STATE_LAST;
			return &head->node;
		}
		if (!blocking) {
			return CDS_WFS_WOULDBLOCK;
		}
		/* busy-loop if head changed under us */
	}
}

/*
 * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 *
 * Returns NULL if stack is empty.
 *
 * __cds_wfs_pop_blocking needs to be synchronized using one of the
 * following techniques:
 *
 * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
 *    section. The caller must wait for a grace period to pass before
 *    freeing the returned node or modifying the cds_wfs_node structure.
 * 2) Using mutual exclusion (e.g. mutexes) to protect
 *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 *
 * "state" saves state flags atomically sampled with pop operation.
 */
static inline
struct cds_wfs_node *
___cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack, int *state)
{
	return ___cds_wfs_pop(u_stack, state, 1);
}

static inline
struct cds_wfs_node *
___cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack)
{
	return ___cds_wfs_pop_with_state_blocking(u_stack, NULL);
}

/*
 * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack.
 *
 * Same as __cds_wfs_pop_with_state_blocking, but returns
 * CDS_WFS_WOULDBLOCK if it needs to block.
 *
 * "state" saves state flags atomically sampled with pop operation.
 */
static inline
struct cds_wfs_node *
___cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack, int *state)
{
	return ___cds_wfs_pop(u_stack, state, 0);
}

/*
 * __cds_wfs_pop_nonblocking: pop a node from the stack.
 *
 * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
 * it needs to block.
 */
static inline
struct cds_wfs_node *
___cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack)
{
	return ___cds_wfs_pop_with_state_nonblocking(u_stack, NULL);
}

/*
 * __cds_wfs_pop_all: pop all nodes from a stack.
 *
 * __cds_wfs_pop_all does not require any synchronization with other
 * push, nor with other __cds_wfs_pop_all, but requires synchronization
 * matching the technique used to synchronize __cds_wfs_pop_blocking:
 *
 * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
 *    section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
 *    must wait for a grace period to pass before freeing the returned
 *    node or modifying the cds_wfs_node structure. However, no RCU
 *    read-side critical section is needed around __cds_wfs_pop_all.
 * 2) Using mutual exclusion (e.g. mutexes) to protect
 *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 */
static inline
struct cds_wfs_head *
___cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack)
{
	struct __cds_wfs_stack *s = u_stack._s;
	struct cds_wfs_head *head;

	/*
	 * Implicit memory barrier after uatomic_xchg() matches implicit
	 * memory barrier before uatomic_xchg() in cds_wfs_push. It
	 * ensures that all nodes of the returned list are consistent.
	 * There is no need to issue memory barriers when iterating on
	 * the returned list, because the full memory barrier issued
	 * prior to each uatomic_cmpxchg, which each write to head, are
	 * taking care to order writes to each node prior to the full
	 * memory barrier after this uatomic_xchg().
	 */
	head = uatomic_xchg(&s->head, CDS_WFS_END);
	if (___cds_wfs_end(head))
		return NULL;
	return head;
}

/*
 * cds_wfs_pop_lock: lock stack pop-protection mutex.
 */
static inline void _cds_wfs_pop_lock(struct cds_wfs_stack *s)
{
	int ret;

	ret = pthread_mutex_lock(&s->lock);
	assert(!ret);
}

/*
 * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
 */
static inline void _cds_wfs_pop_unlock(struct cds_wfs_stack *s)
{
	int ret;

	ret = pthread_mutex_unlock(&s->lock);
	assert(!ret);
}

/*
 * Call __cds_wfs_pop_with_state_blocking with an internal pop mutex held.
 */
static inline
struct cds_wfs_node *
_cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state)
{
	struct cds_wfs_node *retnode;

	_cds_wfs_pop_lock(s);
	retnode = ___cds_wfs_pop_with_state_blocking(s, state);
	_cds_wfs_pop_unlock(s);
	return retnode;
}

/*
 * Call _cds_wfs_pop_with_state_blocking without saving any state.
 */
static inline
struct cds_wfs_node *
_cds_wfs_pop_blocking(struct cds_wfs_stack *s)
{
	return _cds_wfs_pop_with_state_blocking(s, NULL);
}

/*
 * Call __cds_wfs_pop_all with an internal pop mutex held.
 */
static inline
struct cds_wfs_head *
_cds_wfs_pop_all_blocking(struct cds_wfs_stack *s)
{
	struct cds_wfs_head *rethead;

	_cds_wfs_pop_lock(s);
	rethead = ___cds_wfs_pop_all(s);
	_cds_wfs_pop_unlock(s);
	return rethead;
}

/*
 * cds_wfs_first: get first node of a popped stack.
 *
 * Content written into the node before enqueue is guaranteed to be
 * consistent, but no other memory ordering is ensured.
 *
 * Used by for-like iteration macros in urcu/wfstack.h:
 * cds_wfs_for_each_blocking()
 * cds_wfs_for_each_blocking_safe()
 *
 * Returns NULL if popped stack is empty, top stack node otherwise.
 */
static inline struct cds_wfs_node *
_cds_wfs_first(struct cds_wfs_head *head)
{
	if (___cds_wfs_end(head))
		return NULL;
	return &head->node;
}

static inline struct cds_wfs_node *
___cds_wfs_next(struct cds_wfs_node *node, int blocking)
{
	struct cds_wfs_node *next;

	next = ___cds_wfs_node_sync_next(node, blocking);
	/*
	 * CDS_WFS_WOULDBLOCK != CSD_WFS_END, so we can check for end
	 * even if ___cds_wfs_node_sync_next returns CDS_WFS_WOULDBLOCK,
	 * and still return CDS_WFS_WOULDBLOCK.
	 */
	if (___cds_wfs_end(next))
		return NULL;
	return next;
}

/*
 * cds_wfs_next_blocking: get next node of a popped stack.
 *
 * Content written into the node before enqueue is guaranteed to be
 * consistent, but no other memory ordering is ensured.
 *
 * Used by for-like iteration macros in urcu/wfstack.h:
 * cds_wfs_for_each_blocking()
 * cds_wfs_for_each_blocking_safe()
 *
 * Returns NULL if reached end of popped stack, non-NULL next stack
 * node otherwise.
 */
static inline struct cds_wfs_node *
_cds_wfs_next_blocking(struct cds_wfs_node *node)
{
	return ___cds_wfs_next(node, 1);
}


/*
 * cds_wfs_next_nonblocking: get next node of a popped stack.
 *
 * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
 * needs to block.
 */
static inline struct cds_wfs_node *
_cds_wfs_next_nonblocking(struct cds_wfs_node *node)
{
	return ___cds_wfs_next(node, 0);
}

#ifdef __cplusplus
}
#endif

#endif /* _URCU_STATIC_WFSTACK_H */