GRPC Core  43.0.0
sync.h
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1 /*
2  *
3  * Copyright 2015 gRPC authors.
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  *
17  */
18 
19 #ifndef GRPC_SUPPORT_SYNC_H
20 #define GRPC_SUPPORT_SYNC_H
21 
22 /* Platform-specific type declarations of gpr_mu and gpr_cv. */
24 #include <grpc/support/time.h> /* for gpr_timespec */
25 
26 #ifdef __cplusplus
27 extern "C" {
28 #endif
29 
49 #include <grpc/support/sync_generic.h> // IWYU pragma: export
50 
51 #if defined(GPR_CUSTOM_SYNC)
52 #include <grpc/support/sync_custom.h> // IWYU pragma: export
53 #elif defined(GPR_ABSEIL_SYNC)
54 #include <grpc/support/sync_abseil.h> // IWYU pragma: export
55 #elif defined(GPR_POSIX_SYNC)
56 #include <grpc/support/sync_posix.h> // IWYU pragma: export
57 #elif defined(GPR_WINDOWS)
58 #include <grpc/support/sync_windows.h> // IWYU pragma: export
59 #else
60 #error Unable to determine platform for sync
61 #endif
62 
71 GPRAPI void gpr_mu_init(gpr_mu* mu);
72 
75 GPRAPI void gpr_mu_destroy(gpr_mu* mu);
76 
80 GPRAPI void gpr_mu_lock(gpr_mu* mu);
81 
84 GPRAPI void gpr_mu_unlock(gpr_mu* mu);
85 
91 
99 GPRAPI void gpr_cv_init(gpr_cv* cv);
100 
103 GPRAPI void gpr_cv_destroy(gpr_cv* cv);
104 
112 GPRAPI int gpr_cv_wait(gpr_cv* cv, gpr_mu* mu, gpr_timespec abs_deadline);
113 
118 GPRAPI void gpr_cv_signal(gpr_cv* cv);
119 
121 GPRAPI void gpr_cv_broadcast(gpr_cv* cv);
122 
134 GPRAPI void gpr_once_init(gpr_once* once, void (*init_function)(void));
135 
145 
149 GPRAPI void gpr_event_set(gpr_event* ev, void* value);
150 
156 GPRAPI void* gpr_event_get(gpr_event* ev);
157 
163 GPRAPI void* gpr_event_wait(gpr_event* ev, gpr_timespec abs_deadline);
164 
170 GPRAPI void gpr_ref_init(gpr_refcount* r, int n);
171 
173 GPRAPI void gpr_ref(gpr_refcount* r);
174 
178 
180 GPRAPI void gpr_refn(gpr_refcount* r, int n);
181 
185 
189 
199 GPRAPI void gpr_stats_init(gpr_stats_counter* c, intptr_t n);
200 
202 GPRAPI void gpr_stats_inc(gpr_stats_counter* c, intptr_t inc);
203 
205 GPRAPI intptr_t gpr_stats_read(const gpr_stats_counter* c);
206 
210 #if 0
211 
212 #define N 4
213 
214  typedef struct queue {
215  gpr_cv non_empty; /* Signalled when length becomes non-zero. */
216  gpr_cv non_full; /* Signalled when length becomes non-N. */
217  gpr_mu mu; /* Protects all fields below.
218  (That is, except during initialization or
219  destruction, the fields below should be accessed
220  only by a thread that holds mu.) */
221  int head; /* Index of head of queue 0..N-1. */
222  int length; /* Number of valid elements in queue 0..N. */
223  int elem[N]; /* elem[head .. head+length-1] are queue elements. */
224  } queue;
225 
226  /* Initialize *q. */
227  void queue_init(queue *q) {
228  gpr_mu_init(&q->mu);
229  gpr_cv_init(&q->non_empty);
230  gpr_cv_init(&q->non_full);
231  q->head = 0;
232  q->length = 0;
233  }
234 
235  /* Free storage associated with *q. */
236  void queue_destroy(queue *q) {
237  gpr_mu_destroy(&q->mu);
238  gpr_cv_destroy(&q->non_empty);
239  gpr_cv_destroy(&q->non_full);
240  }
241 
242  /* Wait until there is room in *q, then append x to *q. */
243  void queue_append(queue *q, int x) {
244  gpr_mu_lock(&q->mu);
245  /* To wait for a predicate without a deadline, loop on the negation of the
246  predicate, and use gpr_cv_wait(..., gpr_inf_future) inside the loop
247  to release the lock, wait, and reacquire on each iteration. Code that
248  makes the condition true should use gpr_cv_broadcast() on the
249  corresponding condition variable. The predicate must be on state
250  protected by the lock. */
251  while (q->length == N) {
252  gpr_cv_wait(&q->non_full, &q->mu, gpr_inf_future);
253  }
254  if (q->length == 0) { /* Wake threads blocked in queue_remove(). */
255  /* It's normal to use gpr_cv_broadcast() or gpr_signal() while
256  holding the lock. */
257  gpr_cv_broadcast(&q->non_empty);
258  }
259  q->elem[(q->head + q->length) % N] = x;
260  q->length++;
261  gpr_mu_unlock(&q->mu);
262  }
263 
264  /* If it can be done without blocking, append x to *q and return non-zero.
265  Otherwise return 0. */
266  int queue_try_append(queue *q, int x) {
267  int result = 0;
268  if (gpr_mu_trylock(&q->mu)) {
269  if (q->length != N) {
270  if (q->length == 0) { /* Wake threads blocked in queue_remove(). */
271  gpr_cv_broadcast(&q->non_empty);
272  }
273  q->elem[(q->head + q->length) % N] = x;
274  q->length++;
275  result = 1;
276  }
277  gpr_mu_unlock(&q->mu);
278  }
279  return result;
280  }
281 
282  /* Wait until the *q is non-empty or deadline abs_deadline passes. If the
283  queue is non-empty, remove its head entry, place it in *head, and return
284  non-zero. Otherwise return 0. */
285  int queue_remove(queue *q, int *head, gpr_timespec abs_deadline) {
286  int result = 0;
287  gpr_mu_lock(&q->mu);
288  /* To wait for a predicate with a deadline, loop on the negation of the
289  predicate or until gpr_cv_wait() returns true. Code that makes
290  the condition true should use gpr_cv_broadcast() on the corresponding
291  condition variable. The predicate must be on state protected by the
292  lock. */
293  while (q->length == 0 &&
294  !gpr_cv_wait(&q->non_empty, &q->mu, abs_deadline)) {
295  }
296  if (q->length != 0) { /* Queue is non-empty. */
297  result = 1;
298  if (q->length == N) { /* Wake threads blocked in queue_append(). */
299  gpr_cv_broadcast(&q->non_full);
300  }
301  *head = q->elem[q->head];
302  q->head = (q->head + 1) % N;
303  q->length--;
304  } /* else deadline exceeded */
305  gpr_mu_unlock(&q->mu);
306  return result;
307  }
308 #endif /* 0 */
309 
310 #ifdef __cplusplus
311 } // extern "C"
312 #endif
313 
314 #endif /* GRPC_SUPPORT_SYNC_H */
gpr_ref
GPRAPI void gpr_ref(gpr_refcount *r)
Increment the reference count *r.
gpr_mu
pthread_mutex_t gpr_mu
Definition: sync_posix.h:44
gpr_mu_destroy
GPRAPI void gpr_mu_destroy(gpr_mu *mu)
Cause *mu no longer to be initialized, freeing any memory in use.
gpr_once_init
GPRAPI void gpr_once_init(gpr_once *once, void(*init_function)(void))
— One-time initialization —
gpr_stats_read
GPRAPI intptr_t gpr_stats_read(const gpr_stats_counter *c)
Return *c.
sync_windows.h
sync_abseil.h
gpr_cv_wait
GPRAPI int gpr_cv_wait(gpr_cv *cv, gpr_mu *mu, gpr_timespec abs_deadline)
Atomically release *mu and wait on *cv.
gpr_event_init
GPRAPI void gpr_event_init(gpr_event *ev)
— One-time event notification —
gpr_refcount
Definition: sync_generic.h:36
gpr_stats_counter
Definition: sync_generic.h:41
gpr_inf_future
GPRAPI gpr_timespec gpr_inf_future(gpr_clock_type type)
The far future.
gpr_ref_init
GPRAPI void gpr_ref_init(gpr_refcount *r, int n)
— Reference counting —
gpr_cv_init
GPRAPI void gpr_cv_init(gpr_cv *cv)
— Condition variable interface —
gpr_cv_destroy
GPRAPI void gpr_cv_destroy(gpr_cv *cv)
Cause *cv no longer to be initialized, freeing any memory in use.
gpr_once
pthread_once_t gpr_once
Definition: sync_posix.h:47
gpr_event_set
GPRAPI void gpr_event_set(gpr_event *ev, void *value)
Set *ev so that gpr_event_get() and gpr_event_wait() will return value.
sync_generic.h
gpr_stats_inc
GPRAPI void gpr_stats_inc(gpr_stats_counter *c, intptr_t inc)
*c += inc.
gpr_cv_signal
GPRAPI void gpr_cv_signal(gpr_cv *cv)
If any threads are waiting on *cv, wake at least one.
gpr_cv
pthread_cond_t gpr_cv
Definition: sync_posix.h:45
time.h
gpr_mu_lock
GPRAPI void gpr_mu_lock(gpr_mu *mu)
Wait until no thread has a lock on *mu, cause the calling thread to own an exclusive lock on *mu,...
GPRAPI
#define GPRAPI
Definition: port_platform.h:721
gpr_cv_broadcast
GPRAPI void gpr_cv_broadcast(gpr_cv *cv)
Wake all threads waiting on *cv.
gpr_mu_trylock
GPRAPI int gpr_mu_trylock(gpr_mu *mu)
Without blocking, attempt to acquire an exclusive lock on *mu for the calling thread,...
sync_custom.h
gpr_event
Definition: sync_generic.h:28
gpr_mu_unlock
GPRAPI void gpr_mu_unlock(gpr_mu *mu)
Release an exclusive lock on *mu held by the calling thread.
gpr_event_wait
GPRAPI void * gpr_event_wait(gpr_event *ev, gpr_timespec abs_deadline)
Wait until *ev is set by gpr_event_set(ev, ...), or abs_deadline is exceeded, then return gpr_event_g...
gpr_ref_is_unique
GPRAPI int gpr_ref_is_unique(gpr_refcount *r)
Return non-zero iff the reference count of *r is one, and thus is owned by exactly one object.
gpr_stats_init
GPRAPI void gpr_stats_init(gpr_stats_counter *c, intptr_t n)
— Stats counters —
gpr_unref
GPRAPI int gpr_unref(gpr_refcount *r)
Decrement the reference count *r and return non-zero iff it has reached zero.
gpr_refn
GPRAPI void gpr_refn(gpr_refcount *r, int n)
Increment the reference count *r by n.
sync_posix.h
gpr_mu_init
GPRAPI void gpr_mu_init(gpr_mu *mu)
Synchronization primitives for GPR.
gpr_timespec
Analogous to struct timespec.
Definition: time.h:48
gpr_event_get
GPRAPI void * gpr_event_get(gpr_event *ev)
Return the value set by gpr_event_set(ev, ...), or NULL if no such call has completed.
gpr_ref_non_zero
GPRAPI void gpr_ref_non_zero(gpr_refcount *r)
Increment the reference count *r.
port_platform.h