GCC Code Coverage Report

Directory: cvmfs/
File: cvmfs/util/tube.h
Date: 2026-05-10 02:36:07
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 294941685 explicit Link(ItemT *item) : item_(item), next_(NULL), prev_(NULL) { }
46 43 ItemT *item() { return item_; }
47
48 private:
49 ItemT *item_;
50 Link *next_;
51 Link *prev_;
52 };
53
54 206291 Tube() : limit_(uint64_t(-1)), size_(0) { Init(); }
55 2837 explicit Tube(uint64_t limit) : limit_(limit), size_(0) { Init(); }
56 214023 ~Tube() {
57 214397 Link *cursor = head_;
58 do {
59 214440 Link *prev = cursor->prev_;
60
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 214440 delete cursor;
61 214440 cursor = prev;
62
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 214440 } while (cursor != head_);
63 214397 pthread_cond_destroy(&cond_populated_);
64 214397 pthread_cond_destroy(&cond_capacious_);
65 214397 pthread_cond_destroy(&cond_empty_);
66 214397 pthread_mutex_destroy(&lock_);
67 214397 }
68
69 /**
70 * Push an item to the back of the queue. Block if queue is currently full.
71 */
72 279648960 Link *EnqueueBack(ItemT *item) {
73
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 279648960 assert(item != NULL);
74 279648960 MutexLockGuard lock_guard(&lock_);
75
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 291095902 while (size_ == limit_)
76
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 13280240 pthread_cond_wait(&cond_capacious_, &lock_);
77
78
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 277815662 Link *link = new Link(item);
79 276244044 link->next_ = head_->next_;
80 276244044 link->prev_ = head_;
81 276244044 head_->next_->prev_ = link;
82 276244044 head_->next_ = link;
83 276244044 size_++;
84 276244044 int retval = pthread_cond_signal(&cond_populated_);
85
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 280691956 assert(retval == 0);
86 279505982 return link;
87 280691956 }
88
89 /**
90 * Push an item to the front of the queue. Block if queue currently full.
91 */
92 17296599 Link *EnqueueFront(ItemT *item) {
93
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 17296599 assert(item != NULL);
94 17296599 MutexLockGuard lock_guard(&lock_);
95
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 17296795 while (size_ == limit_)
96
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 282 pthread_cond_wait(&cond_capacious_, &lock_);
97
98
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 17296513 Link *link = new Link(item);
99 17296255 link->next_ = head_;
100 17296255 link->prev_ = head_->prev_;
101 17296255 head_->prev_->next_ = link;
102 17296255 head_->prev_ = link;
103 17296255 size_++;
104 17296255 int retval = pthread_cond_signal(&cond_populated_);
105
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 17296126 assert(retval == 0);
106 17296427 return link;
107 17296126 }
108
109 /**
110 * Remove any link from the queue and return its item, including first/last
111 * element.
112 */
113 47 ItemT *Slice(Link *link) {
114 47 MutexLockGuard lock_guard(&lock_);
115 47 return SliceUnlocked(link);
116 47 }
117
118 /**
119 * Remove and return the first element from the queue. Block if tube is
120 * empty.
121 */
122 294771535 ItemT *PopFront() {
123 294771535 MutexLockGuard lock_guard(&lock_);
124
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 403496285 while (size_ == 0)
125
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 108589783 pthread_cond_wait(&cond_populated_, &lock_);
126 588344940 return SliceUnlocked(head_->prev_);
127 293433417 }
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 17279131 ItemT *TryPopFront() {
137 17279131 MutexLockGuard lock_guard(&lock_);
138 // Note that we don't need to wait for a signal to arrive
139
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 17290139 if (size_ == 0)
140 15829923 return NULL;
141 1460216 return SliceUnlocked(head_->prev_);
142 17290139 }
143
144 /**
145 * Remove and return the last element from the queue. Block if tube is
146 * empty.
147 */
148 6628 ItemT *PopBack() {
149 6628 MutexLockGuard lock_guard(&lock_);
150
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 8320 while (size_ == 0)
151
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 1692 pthread_cond_wait(&cond_populated_, &lock_);
152 13256 return SliceUnlocked(head_->next_);
153 6628 }
154
155 /**
156 * Blocks until the tube is empty
157 */
158 2084 void Wait() {
159 2084 MutexLockGuard lock_guard(&lock_);
160
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 2822 while (size_ > 0)
161
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 738 pthread_cond_wait(&cond_empty_, &lock_);
162 2084 }
163
164 10058 bool IsEmpty() {
165 10058 MutexLockGuard lock_guard(&lock_);
166 20116 return size_ == 0;
167 10058 }
168
169 388 uint64_t size() {
170 388 MutexLockGuard lock_guard(&lock_);
171 776 return size_;
172 388 }
173
174 private:
175 210469 void Init() {
176 210469 Link *sentinel = new Link(NULL);
177 210469 head_ = sentinel;
178 210469 head_->next_ = head_->prev_ = sentinel;
179
180 210469 int retval = pthread_mutex_init(&lock_, NULL);
181
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 210469 assert(retval == 0);
182 210469 retval = pthread_cond_init(&cond_populated_, NULL);
183
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 210469 assert(retval == 0);
184 210469 retval = pthread_cond_init(&cond_capacious_, NULL);
185
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 210469 assert(retval == 0);
186 210469 retval = pthread_cond_init(&cond_empty_, NULL);
187
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 210469 assert(retval == 0);
188 210469 }
189
190 295565029 ItemT *SliceUnlocked(Link *link) {
191 // Cannot delete the sentinel link
192
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 295565029 assert(link != head_);
193 295565029 link->prev_->next_ = link->next_;
194 295565029 link->next_->prev_ = link->prev_;
195 295565029 ItemT *item = link->item_;
196
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 295565029 delete link;
197 298333173 size_--;
198 298333173 int retval = pthread_cond_signal(&cond_capacious_);
199
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 297559325 assert(retval == 0);
200
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 297559325 if (size_ == 0) {
201 122688346 retval = pthread_cond_broadcast(&cond_empty_);
202
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 122749056 assert(retval == 0);
203 }
204 296298559 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 16857 TubeGroup() : is_active_(false) { atomic_init32(&round_robin_); }
248
249 16846 ~TubeGroup() {
250
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 214148 for (unsigned i = 0; i < tubes_.size(); ++i)
251
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 197302 delete tubes_[i];
252 16846 }
253
254 197447 void TakeTube(Tube<ItemT> *t) {
255
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 197447 assert(!is_active_);
256 197447 tubes_.push_back(t);
257 197447 }
258
259 16857 void Activate() {
260
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 16857 assert(!is_active_);
261
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 16857 assert(!tubes_.empty());
262 16857 is_active_ = true;
263 16857 }
264
265 /**
266 * Like Tube::EnqueueBack(), but pick a tube according to ItemT::tag()
267 */
268 114679541 typename Tube<ItemT>::Link *Dispatch(ItemT *item) {
269
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 114679541 assert(is_active_);
270
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 114679541 unsigned tube_idx = (tubes_.size() == 1) ? 0
271 90191693 : (item->tag() % tubes_.size());
272 113812989 return tubes_[tube_idx]->EnqueueBack(item);
273 }
274
275 /**
276 * Like Tube::EnqueueBack(), use tubes one after another
277 */
278 9503243 typename Tube<ItemT>::Link *DispatchAny(ItemT *item) {
279
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 9503243 assert(is_active_);
280
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 9503243 unsigned tube_idx = (tubes_.size() == 1)
281 ? 0
282 9503235 : (atomic_xadd32(&round_robin_, 1) % tubes_.size());
283 9503243 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