GCC Code Coverage Report

Directory: cvmfs/
File: cvmfs/util/tube.h
Date: 2025-12-21 02:39:23
Exec Total Coverage
Lines: 130 130 100.0%
Branches: 49 74 66.2%
Line Branch Exec Source
1 /**
2 * This file is part of the CernVM File System.
3 */
4
5 #ifndef CVMFS_UTIL_TUBE_H_
6 #define CVMFS_UTIL_TUBE_H_
7
8 #include <pthread.h>
9 #include <stdint.h>
10
11 #include <cassert>
12 #include <cstddef>
13 #include <vector>
14
15 #include "util/atomic.h"
16 #include "util/mutex.h"
17 #include "util/single_copy.h"
18
19 /**
20 * A thread-safe, doubly linked list of links containing pointers to ItemT. The
21 * ItemT elements are not owned by the Tube. FIFO or LIFO semantics. Using
22 * Slice(), items at arbitrary locations in the tube can be removed, too.
23 *
24 *
25 * The layout of the linked list is as follows:
26 *
27 * --------------------------------------------------------------
28 * | |
29 * --> I$n$ (back) <--> I2 <--> ... <--> I1 (front) <--> HEAD <--
30 *
31 * The tube links the steps in the file processing pipeline. It connects
32 * multiple producers to multiple consumers and can throttle the producers if a
33 * limit for the tube size is set.
34 *
35 * Internally, uses conditional variables to block when threads try to pop from
36 * the empty tube or insert into the full tube.
37 */
38 template<class ItemT>
39 class Tube : SingleCopy {
40 public:
41 class Link : SingleCopy {
42 friend class Tube<ItemT>;
43
44 public:
45 302773843 explicit Link(ItemT *item) : item_(item), next_(NULL), prev_(NULL) { }
46 45 ItemT *item() { return item_; }
47
48 private:
49 ItemT *item_;
50 Link *next_;
51 Link *prev_;
52 };
53
54 229830 Tube() : limit_(uint64_t(-1)), size_(0) { Init(); }
55 2874 explicit Tube(uint64_t limit) : limit_(limit), size_(0) { Init(); }
56 237963 ~Tube() {
57 238306 Link *cursor = head_;
58 do {
59 238323 Link *prev = cursor->prev_;
60
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 238323 delete cursor;
61 238323 cursor = prev;
62
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 238323 } while (cursor != head_);
63 238306 pthread_cond_destroy(&cond_populated_);
64 238306 pthread_cond_destroy(&cond_capacious_);
65 238306 pthread_cond_destroy(&cond_empty_);
66 238306 pthread_mutex_destroy(&lock_);
67 238306 }
68
69 /**
70 * Push an item to the back of the queue. Block if queue is currently full.
71 */
72 296989864 Link *EnqueueBack(ItemT *item) {
73
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 296989864 assert(item != NULL);
74 296989864 MutexLockGuard lock_guard(&lock_);
75
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 312882775 while (size_ == limit_)
76
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 16469622 pthread_cond_wait(&cond_capacious_, &lock_);
77
78
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 296413153 Link *link = new Link(item);
79 294468115 link->next_ = head_->next_;
80 294468115 link->prev_ = head_;
81 294468115 head_->next_->prev_ = link;
82 294468115 head_->next_ = link;
83 294468115 size_++;
84 294468115 int retval = pthread_cond_signal(&cond_populated_);
85
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 297864445 assert(retval == 0);
86 296891485 return link;
87 297864445 }
88
89 /**
90 * Push an item to the front of the queue. Block if queue currently full.
91 */
92 6858260 Link *EnqueueFront(ItemT *item) {
93
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 6858260 assert(item != NULL);
94 6858260 MutexLockGuard lock_guard(&lock_);
95
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 6858478 while (size_ == limit_)
96
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 252 pthread_cond_wait(&cond_capacious_, &lock_);
97
98
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 6858226 Link *link = new Link(item);
99 6858209 link->next_ = head_;
100 6858209 link->prev_ = head_->prev_;
101 6858209 head_->prev_->next_ = link;
102 6858209 head_->prev_ = link;
103 6858209 size_++;
104 6858209 int retval = pthread_cond_signal(&cond_populated_);
105
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 6858175 assert(retval == 0);
106 6858226 return link;
107 6858175 }
108
109 /**
110 * Remove any link from the queue and return its item, including first/last
111 * element.
112 */
113 67 ItemT *Slice(Link *link) {
114 67 MutexLockGuard lock_guard(&lock_);
115 67 return SliceUnlocked(link);
116 67 }
117
118 /**
119 * Remove and return the first element from the queue. Block if tube is
120 * empty.
121 */
122 302404185 ItemT *PopFront() {
123 302404185 MutexLockGuard lock_guard(&lock_);
124
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 417606449 while (size_ == 0)
125
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 114104152 pthread_cond_wait(&cond_populated_, &lock_);
126 604987448 return SliceUnlocked(head_->prev_);
127 300609557 }
128
129 /**
130 * Remove and return the first element from the queue if there is any.
131 * Equivalent to an antomic
132 * ItemT item = NULL;
133 * if (!IsEmpty())
134 * item = PopFront();
135 */
136 6850057 ItemT *TryPopFront() {
137 6850057 MutexLockGuard lock_guard(&lock_);
138 // Note that we don't need to wait for a signal to arrive
139
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 6852148 if (size_ == 0)
140 6273653 return NULL;
141 578495 return SliceUnlocked(head_->prev_);
142 6852148 }
143
144 /**
145 * Remove and return the last element from the queue. Block if tube is
146 * empty.
147 */
148 6180 ItemT *PopBack() {
149 6180 MutexLockGuard lock_guard(&lock_);
150
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 7608 while (size_ == 0)
151
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 1428 pthread_cond_wait(&cond_populated_, &lock_);
152 12360 return SliceUnlocked(head_->next_);
153 6180 }
154
155 /**
156 * Blocks until the tube is empty
157 */
158 2131 void Wait() {
159 2131 MutexLockGuard lock_guard(&lock_);
160
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 3040 while (size_ > 0)
161
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 909 pthread_cond_wait(&cond_empty_, &lock_);
162 2131 }
163
164 14105 bool IsEmpty() {
165 14105 MutexLockGuard lock_guard(&lock_);
166 28210 return size_ == 0;
167 14105 }
168
169 722 uint64_t size() {
170 722 MutexLockGuard lock_guard(&lock_);
171 1444 return size_;
172 722 }
173
174 private:
175 234206 void Init() {
176 234206 Link *sentinel = new Link(NULL);
177 234206 head_ = sentinel;
178 234206 head_->next_ = head_->prev_ = sentinel;
179
180 234206 int retval = pthread_mutex_init(&lock_, NULL);
181
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 234206 assert(retval == 0);
182 234206 retval = pthread_cond_init(&cond_populated_, NULL);
183
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 234206 assert(retval == 0);
184 234206 retval = pthread_cond_init(&cond_capacious_, NULL);
185
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 234206 assert(retval == 0);
186 234206 retval = pthread_cond_init(&cond_empty_, NULL);
187
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 234206 assert(retval == 0);
188 234206 }
189
190 302457560 ItemT *SliceUnlocked(Link *link) {
191 // Cannot delete the sentinel link
192
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 302457560 assert(link != head_);
193 302457560 link->prev_->next_ = link->next_;
194 302457560 link->next_->prev_ = link->prev_;
195 302457560 ItemT *item = link->item_;
196
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 302457560 delete link;
197 304082409 size_--;
198 304082409 int retval = pthread_cond_signal(&cond_capacious_);
199
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 301686727 assert(retval == 0);
200
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 301686727 if (size_ == 0) {
201 123444154 retval = pthread_cond_broadcast(&cond_empty_);
202
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 123462874 assert(retval == 0);
203 }
204 301962159 return item;
205 }
206
207
208 /**
209 * Adding new item blocks as long as limit_ == size_
210 */
211 uint64_t limit_;
212 /**
213 * The current number of links in the list
214 */
215 uint64_t size_;
216 /**
217 * Sentinel element in front of the first (front) element
218 */
219 Link *head_;
220 /**
221 * Protects all internal state
222 */
223 pthread_mutex_t lock_;
224 /**
225 * Signals if there are items enqueued
226 */
227 pthread_cond_t cond_populated_;
228 /**
229 * Signals if there is space to enqueue more items
230 */
231 pthread_cond_t cond_capacious_;
232 /**
233 * Signals if the queue runs empty
234 */
235 pthread_cond_t cond_empty_;
236 };
237
238
239 /**
240 * A tube group manages a fixed set of Tubes and dispatches items among them in
241 * such a way that items with the same tag (a positive integer) are all sent
242 * to the same tube.
243 */
244 template<class ItemT>
245 class TubeGroup : SingleCopy {
246 public:
247 19645 TubeGroup() : is_active_(false) { atomic_init32(&round_robin_); }
248
249 19634 ~TubeGroup() {
250
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 237987 for (unsigned i = 0; i < tubes_.size(); ++i)
251
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 218353 delete tubes_[i];
252 19634 }
253
254 218498 void TakeTube(Tube<ItemT> *t) {
255
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 218498 assert(!is_active_);
256 218498 tubes_.push_back(t);
257 218498 }
258
259 19645 void Activate() {
260
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 19645 assert(!is_active_);
261
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 19645 assert(!tubes_.empty());
262 19645 is_active_ = true;
263 19645 }
264
265 /**
266 * Like Tube::EnqueueBack(), but pick a tube according to ItemT::tag()
267 */
268 120133174 typename Tube<ItemT>::Link *Dispatch(ItemT *item) {
269
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 120133174 assert(is_active_);
270
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 120133174 unsigned tube_idx = (tubes_.size() == 1) ? 0
271 92971793 : (item->tag() % tubes_.size());
272 119503870 return tubes_[tube_idx]->EnqueueBack(item);
273 }
274
275 /**
276 * Like Tube::EnqueueBack(), use tubes one after another
277 */
278 9752980 typename Tube<ItemT>::Link *DispatchAny(ItemT *item) {
279
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 9752980 assert(is_active_);
280
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 9752980 unsigned tube_idx = (tubes_.size() == 1)
281 ? 0
282 9752896 : (atomic_xadd32(&round_robin_, 1) % tubes_.size());
283 9752980 return tubes_[tube_idx]->EnqueueBack(item);
284 }
285
286 private:
287 bool is_active_;
288 std::vector<Tube<ItemT> *> tubes_;
289 atomic_int32 round_robin_;
290 };
291
292 #endif // CVMFS_UTIL_TUBE_H_
293