GCC Code Coverage Report

Directory: cvmfs/
File: cvmfs/util/tube.h
Date: 2025-11-23 02:35:30
Exec Total Coverage
Lines: 130 130 100.0%
Branches: 50 74 67.6%
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 341147341 explicit Link(ItemT *item) : item_(item), next_(NULL), prev_(NULL) { }
46 25 ItemT *item() { return item_; }
47
48 private:
49 ItemT *item_;
50 Link *next_;
51 Link *prev_;
52 };
53
54 238345 Tube() : limit_(uint64_t(-1)), size_(0) { Init(); }
55 3072 explicit Tube(uint64_t limit) : limit_(limit), size_(0) { Init(); }
56 246621 ~Tube() {
57 246996 Link *cursor = head_;
58 do {
59 246997 Link *prev = cursor->prev_;
60
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 246997 delete cursor;
61 246997 cursor = prev;
62
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 246997 } while (cursor != head_);
63 246996 pthread_cond_destroy(&cond_populated_);
64 246996 pthread_cond_destroy(&cond_capacious_);
65 246996 pthread_cond_destroy(&cond_empty_);
66 246996 pthread_mutex_destroy(&lock_);
67 246996 }
68
69 /**
70 * Push an item to the back of the queue. Block if queue is currently full.
71 */
72 343008598 Link *EnqueueBack(ItemT *item) {
73
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 343008598 assert(item != NULL);
74 343008598 MutexLockGuard lock_guard(&lock_);
75
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 359328102 while (size_ == limit_)
76
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 18323548 pthread_cond_wait(&cond_capacious_, &lock_);
77
78
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 341004554 Link *link = new Link(item);
79 338832438 link->next_ = head_->next_;
80 338832438 link->prev_ = head_;
81 338832438 head_->next_->prev_ = link;
82 338832438 head_->next_ = link;
83 338832438 size_++;
84 338832438 int retval = pthread_cond_signal(&cond_populated_);
85
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 344352990 assert(retval == 0);
86 343145060 return link;
87 344352990 }
88
89 /**
90 * Push an item to the front of the queue. Block if queue currently full.
91 */
92 418909 Link *EnqueueFront(ItemT *item) {
93
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 418909 assert(item != NULL);
94 418909 MutexLockGuard lock_guard(&lock_);
95
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 419380 while (size_ == limit_)
96
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 470 pthread_cond_wait(&cond_capacious_, &lock_);
97
98
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 418910 Link *link = new Link(item);
99 418909 link->next_ = head_;
100 418909 link->prev_ = head_->prev_;
101 418909 head_->prev_->next_ = link;
102 418909 head_->prev_ = link;
103 418909 size_++;
104 418909 int retval = pthread_cond_signal(&cond_populated_);
105
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 418909 assert(retval == 0);
106 418909 return link;
107 418909 }
108
109 /**
110 * Remove any link from the queue and return its item, including first/last
111 * element.
112 */
113 55 ItemT *Slice(Link *link) {
114 55 MutexLockGuard lock_guard(&lock_);
115 55 return SliceUnlocked(link);
116 55 }
117
118 /**
119 * Remove and return the first element from the queue. Block if tube is
120 * empty.
121 */
122 343212209 ItemT *PopFront() {
123 343212209 MutexLockGuard lock_guard(&lock_);
124
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 475819581 while (size_ == 0)
125
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 133283775 pthread_cond_wait(&cond_populated_, &lock_);
126 683680938 return SliceUnlocked(head_->prev_);
127 340443256 }
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 411877 ItemT *TryPopFront() {
137 411877 MutexLockGuard lock_guard(&lock_);
138 // Note that we don't need to wait for a signal to arrive
139
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 411963 if (size_ == 0)
140 377281 return NULL;
141 34682 return SliceUnlocked(head_->prev_);
142 411963 }
143
144 /**
145 * Remove and return the last element from the queue. Block if tube is
146 * empty.
147 */
148 6968 ItemT *PopBack() {
149 6968 MutexLockGuard lock_guard(&lock_);
150
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 8752 while (size_ == 0)
151
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 1784 pthread_cond_wait(&cond_populated_, &lock_);
152 13936 return SliceUnlocked(head_->next_);
153 6968 }
154
155 /**
156 * Blocks until the tube is empty
157 */
158 2272 void Wait() {
159 2272 MutexLockGuard lock_guard(&lock_);
160
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 3250 while (size_ > 0)
161
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 978 pthread_cond_wait(&cond_empty_, &lock_);
162 2272 }
163
164 7968 bool IsEmpty() {
165 7968 MutexLockGuard lock_guard(&lock_);
166 15936 return size_ == 0;
167 7968 }
168
169 506 uint64_t size() {
170 506 MutexLockGuard lock_guard(&lock_);
171 1012 return size_;
172 506 }
173
174 private:
175 242989 void Init() {
176 242989 Link *sentinel = new Link(NULL);
177 242989 head_ = sentinel;
178 242989 head_->next_ = head_->prev_ = sentinel;
179
180 242989 int retval = pthread_mutex_init(&lock_, NULL);
181
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 242989 assert(retval == 0);
182 242989 retval = pthread_cond_init(&cond_populated_, NULL);
183
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 242989 assert(retval == 0);
184 242989 retval = pthread_cond_init(&cond_capacious_, NULL);
185
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 242989 assert(retval == 0);
186 242989 retval = pthread_cond_init(&cond_empty_, NULL);
187
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 242989 assert(retval == 0);
188 242989 }
189
190 341532100 ItemT *SliceUnlocked(Link *link) {
191 // Cannot delete the sentinel link
192
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 341532100 assert(link != head_);
193 341532100 link->prev_->next_ = link->next_;
194 341532100 link->next_->prev_ = link->prev_;
195 341532100 ItemT *item = link->item_;
196
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 341532100 delete link;
197 344439940 size_--;
198 344439940 int retval = pthread_cond_signal(&cond_capacious_);
199
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 343690285 assert(retval == 0);
200
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 343690285 if (size_ == 0) {
201 148179607 retval = pthread_cond_broadcast(&cond_empty_);
202
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 148202879 assert(retval == 0);
203 }
204 342214226 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 19892 TubeGroup() : is_active_(false) { atomic_init32(&round_robin_); }
248
249 19881 ~TubeGroup() {
250
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 249153 for (unsigned i = 0; i < tubes_.size(); ++i)
251
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 229272 delete tubes_[i];
252 19881 }
253
254 229417 void TakeTube(Tube<ItemT> *t) {
255
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 229417 assert(!is_active_);
256 229417 tubes_.push_back(t);
257 229417 }
258
259 19892 void Activate() {
260
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 19892 assert(!is_active_);
261
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 19892 assert(!tubes_.empty());
262 19892 is_active_ = true;
263 19892 }
264
265 /**
266 * Like Tube::EnqueueBack(), but pick a tube according to ItemT::tag()
267 */
268 140282719 typename Tube<ItemT>::Link *Dispatch(ItemT *item) {
269
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 140282719 assert(is_active_);
270
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 140282719 unsigned tube_idx = (tubes_.size() == 1) ? 0
271 109370545 : (item->tag() % tubes_.size());
272 138866839 return tubes_[tube_idx]->EnqueueBack(item);
273 }
274
275 /**
276 * Like Tube::EnqueueBack(), use tubes one after another
277 */
278 11503016 typename Tube<ItemT>::Link *DispatchAny(ItemT *item) {
279
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 11503016 assert(is_active_);
280
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 11503016 unsigned tube_idx = (tubes_.size() == 1)
281 ? 0
282 11502964 : (atomic_xadd32(&round_robin_, 1) % tubes_.size());
283 11503016 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