GCC Code Coverage Report

Directory: cvmfs/
File: cvmfs/util/tube.h
Date: 2025-12-14 02:35:46
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 369951347 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 284683 Tube() : limit_(uint64_t(-1)), size_(0) { Init(); }
55 3014 explicit Tube(uint64_t limit) : limit_(limit), size_(0) { Init(); }
56 293231 ~Tube() {
57 293519 Link *cursor = head_;
58 do {
59 293557 Link *prev = cursor->prev_;
60
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 293557 delete cursor;
61 293557 cursor = prev;
62
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 293557 } while (cursor != head_);
63 293519 pthread_cond_destroy(&cond_populated_);
64 293519 pthread_cond_destroy(&cond_capacious_);
65 293519 pthread_cond_destroy(&cond_empty_);
66 293519 pthread_mutex_destroy(&lock_);
67 293519 }
68
69 /**
70 * Push an item to the back of the queue. Block if queue is currently full.
71 */
72 356089772 Link *EnqueueBack(ItemT *item) {
73
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 356089772 assert(item != NULL);
74 356089772 MutexLockGuard lock_guard(&lock_);
75
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 373886403 while (size_ == limit_)
76
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 18759862 pthread_cond_wait(&cond_capacious_, &lock_);
77
78
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 355126541 Link *link = new Link(item);
79 352770093 link->next_ = head_->next_;
80 352770093 link->prev_ = head_;
81 352770093 head_->next_->prev_ = link;
82 352770093 head_->next_ = link;
83 352770093 size_++;
84 352770093 int retval = pthread_cond_signal(&cond_populated_);
85
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 357137769 assert(retval == 0);
86 356008763 return link;
87 357137769 }
88
89 /**
90 * Push an item to the front of the queue. Block if queue currently full.
91 */
92 15302759 Link *EnqueueFront(ItemT *item) {
93
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 15302759 assert(item != NULL);
94 15302759 MutexLockGuard lock_guard(&lock_);
95
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 15302759 while (size_ == limit_)
96
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 76 pthread_cond_wait(&cond_capacious_, &lock_);
97
98
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 15302683 Link *link = new Link(item);
99 15302721 link->next_ = head_;
100 15302721 link->prev_ = head_->prev_;
101 15302721 head_->prev_->next_ = link;
102 15302721 head_->prev_ = link;
103 15302721 size_++;
104 15302721 int retval = pthread_cond_signal(&cond_populated_);
105
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 15302759 assert(retval == 0);
106 15302683 return link;
107 15302759 }
108
109 /**
110 * Remove any link from the queue and return its item, including first/last
111 * element.
112 */
113 92 ItemT *Slice(Link *link) {
114 92 MutexLockGuard lock_guard(&lock_);
115 92 return SliceUnlocked(link);
116 92 }
117
118 /**
119 * Remove and return the first element from the queue. Block if tube is
120 * empty.
121 */
122 368918934 ItemT *PopFront() {
123 368918934 MutexLockGuard lock_guard(&lock_);
124
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 508796497 while (size_ == 0)
125
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 138443852 pthread_cond_wait(&cond_populated_, &lock_);
126 738346554 return SliceUnlocked(head_->prev_);
127 366782947 }
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 15291165 ItemT *TryPopFront() {
137 15291165 MutexLockGuard lock_guard(&lock_);
138 // Note that we don't need to wait for a signal to arrive
139
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 15296903 if (size_ == 0)
140 14005245 return NULL;
141 1291658 return SliceUnlocked(head_->prev_);
142 15296903 }
143
144 /**
145 * Remove and return the last element from the queue. Block if tube is
146 * empty.
147 */
148 5899 ItemT *PopBack() {
149 5899 MutexLockGuard lock_guard(&lock_);
150
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 7875 while (size_ == 0)
151
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 1976 pthread_cond_wait(&cond_populated_, &lock_);
152 11798 return SliceUnlocked(head_->next_);
153 5899 }
154
155 /**
156 * Blocks until the tube is empty
157 */
158 2705 void Wait() {
159 2705 MutexLockGuard lock_guard(&lock_);
160
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 3818 while (size_ > 0)
161
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 1113 pthread_cond_wait(&cond_empty_, &lock_);
162 2705 }
163
164 18283 bool IsEmpty() {
165 18283 MutexLockGuard lock_guard(&lock_);
166 36566 return size_ == 0;
167 18283 }
168
169 859 uint64_t size() {
170 859 MutexLockGuard lock_guard(&lock_);
171 1718 return size_;
172 859 }
173
174 private:
175 289559 void Init() {
176 289559 Link *sentinel = new Link(NULL);
177 289559 head_ = sentinel;
178 289559 head_->next_ = head_->prev_ = sentinel;
179
180 289559 int retval = pthread_mutex_init(&lock_, NULL);
181
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 289559 assert(retval == 0);
182 289559 retval = pthread_cond_init(&cond_populated_, NULL);
183
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 289559 assert(retval == 0);
184 289559 retval = pthread_cond_init(&cond_capacious_, NULL);
185
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 289559 assert(retval == 0);
186 289559 retval = pthread_cond_init(&cond_empty_, NULL);
187
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 289559 assert(retval == 0);
188 289559 }
189
190 369685982 ItemT *SliceUnlocked(Link *link) {
191 // Cannot delete the sentinel link
192
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 369685982 assert(link != head_);
193 369685982 link->prev_->next_ = link->next_;
194 369685982 link->next_->prev_ = link->prev_;
195 369685982 ItemT *item = link->item_;
196
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 369685982 delete link;
197 371823512 size_--;
198 371823512 int retval = pthread_cond_signal(&cond_capacious_);
199
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 368770160 assert(retval == 0);
200
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 368770160 if (size_ == 0) {
201 151807796 retval = pthread_cond_broadcast(&cond_empty_);
202
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 151826590 assert(retval == 0);
203 }
204 369109204 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 23238 TubeGroup() : is_active_(false) { atomic_init32(&round_robin_); }
248
249 23227 ~TubeGroup() {
250
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 293105 for (unsigned i = 0; i < tubes_.size(); ++i)
251
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 269878 delete tubes_[i];
252 23227 }
253
254 270023 void TakeTube(Tube<ItemT> *t) {
255
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 270023 assert(!is_active_);
256 270023 tubes_.push_back(t);
257 270023 }
258
259 23238 void Activate() {
260
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 23238 assert(!is_active_);
261
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 23238 assert(!tubes_.empty());
262 23238 is_active_ = true;
263 23238 }
264
265 /**
266 * Like Tube::EnqueueBack(), but pick a tube according to ItemT::tag()
267 */
268 144322150 typename Tube<ItemT>::Link *Dispatch(ItemT *item) {
269
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 144322150 assert(is_active_);
270
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 144322150 unsigned tube_idx = (tubes_.size() == 1) ? 0
271 111909547 : (item->tag() % tubes_.size());
272 143494762 return tubes_[tube_idx]->EnqueueBack(item);
273 }
274
275 /**
276 * Like Tube::EnqueueBack(), use tubes one after another
277 */
278 11753167 typename Tube<ItemT>::Link *DispatchAny(ItemT *item) {
279
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 11753167 assert(is_active_);
280
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 11753167 unsigned tube_idx = (tubes_.size() == 1)
281 ? 0
282 11753079 : (atomic_xadd32(&round_robin_, 1) % tubes_.size());
283 11753167 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