1
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#include "kmp.h"
11#include "kmp_i18n.h"
12#include "kmp_io.h"
13#include "kmp_str.h"
14#if OMPT_SUPPORT
15#include "ompt-specific.h"
16#endif
17
18/*!
19@ingroup CANCELLATION
20@param loc_ref location of the original task directive
21@param gtid Global thread ID of encountering thread
22@param cncl_kind Cancellation kind (parallel, for, sections, taskgroup)
23
24@return returns true if the cancellation request has been activated and the
25execution thread needs to proceed to the end of the canceled region.
26
27Request cancellation of the binding OpenMP region.
28*/
29kmp_int32 __kmpc_cancel(ident_t *loc_ref, kmp_int32 gtid, kmp_int32 cncl_kind) {
30 kmp_info_t *this_thr = __kmp_threads[gtid];
31
32 KC_TRACE(10, ("__kmpc_cancel: T#%d request %d OMP_CANCELLATION=%d\n", gtid,
33 cncl_kind, __kmp_omp_cancellation));
34
35 KMP_DEBUG_ASSERT(cncl_kind != cancel_noreq);
36 KMP_DEBUG_ASSERT(cncl_kind == cancel_parallel || cncl_kind == cancel_loop ||
37 cncl_kind == cancel_sections ||
38 cncl_kind == cancel_taskgroup);
39 KMP_DEBUG_ASSERT(__kmp_get_gtid() == gtid);
40
41 if (__kmp_omp_cancellation) {
42 switch (cncl_kind) {
43 case cancel_parallel:
44 case cancel_loop:
45 case cancel_sections:
46 // cancellation requests for parallel and worksharing constructs
47 // are handled through the team structure
48 {
49 kmp_team_t *this_team = this_thr->th.th_team;
50 KMP_DEBUG_ASSERT(this_team);
51 kmp_int32 old = cancel_noreq;
52 this_team->t.t_cancel_request.compare_exchange_strong(i1&: old, i2: cncl_kind);
53 if (old == cancel_noreq || old == cncl_kind) {
54// we do not have a cancellation request in this team or we do have
55// one that matches the current request -> cancel
56#if OMPT_SUPPORT && OMPT_OPTIONAL
57 if (ompt_enabled.ompt_callback_cancel) {
58 ompt_data_t *task_data;
59 __ompt_get_task_info_internal(ancestor_level: 0, NULL, task_data: &task_data, NULL, NULL,
60 NULL);
61 ompt_cancel_flag_t type = ompt_cancel_parallel;
62 if (cncl_kind == cancel_parallel)
63 type = ompt_cancel_parallel;
64 else if (cncl_kind == cancel_loop)
65 type = ompt_cancel_loop;
66 else if (cncl_kind == cancel_sections)
67 type = ompt_cancel_sections;
68 ompt_callbacks.ompt_callback(ompt_callback_cancel)(
69 task_data, type | ompt_cancel_activated,
70 OMPT_GET_RETURN_ADDRESS(0));
71 }
72#endif // OMPT_SUPPORT && OMPT_OPTIONAL
73 return 1 /* true */;
74 }
75 break;
76 }
77 case cancel_taskgroup:
78 // cancellation requests for a task group
79 // are handled through the taskgroup structure
80 {
81 kmp_taskdata_t *task;
82 kmp_taskgroup_t *taskgroup;
83
84 task = this_thr->th.th_current_task;
85 KMP_DEBUG_ASSERT(task);
86
87 taskgroup = task->td_taskgroup;
88 if (taskgroup) {
89 kmp_int32 old = cancel_noreq;
90 taskgroup->cancel_request.compare_exchange_strong(i1&: old, i2: cncl_kind);
91 if (old == cancel_noreq || old == cncl_kind) {
92// we do not have a cancellation request in this taskgroup or we do
93// have one that matches the current request -> cancel
94#if OMPT_SUPPORT && OMPT_OPTIONAL
95 if (ompt_enabled.ompt_callback_cancel) {
96 ompt_data_t *task_data;
97 __ompt_get_task_info_internal(ancestor_level: 0, NULL, task_data: &task_data, NULL, NULL,
98 NULL);
99 ompt_callbacks.ompt_callback(ompt_callback_cancel)(
100 task_data, ompt_cancel_taskgroup | ompt_cancel_activated,
101 OMPT_GET_RETURN_ADDRESS(0));
102 }
103#endif
104 return 1 /* true */;
105 }
106 } else {
107 // TODO: what needs to happen here?
108 // the specification disallows cancellation w/o taskgroups
109 // so we might do anything here, let's abort for now
110 KMP_ASSERT(0 /* false */);
111 }
112 }
113 break;
114 default:
115 KMP_ASSERT(0 /* false */);
116 }
117 }
118
119 // ICV OMP_CANCELLATION=false, so we ignored this cancel request
120 KMP_DEBUG_ASSERT(!__kmp_omp_cancellation);
121 return 0 /* false */;
122}
123
124/*!
125@ingroup CANCELLATION
126@param loc_ref location of the original task directive
127@param gtid Global thread ID of encountering thread
128@param cncl_kind Cancellation kind (parallel, for, sections, taskgroup)
129
130@return returns true if a matching cancellation request has been flagged in the
131RTL and the encountering thread has to cancel..
132
133Cancellation point for the encountering thread.
134*/
135kmp_int32 __kmpc_cancellationpoint(ident_t *loc_ref, kmp_int32 gtid,
136 kmp_int32 cncl_kind) {
137 kmp_info_t *this_thr = __kmp_threads[gtid];
138
139 KC_TRACE(10,
140 ("__kmpc_cancellationpoint: T#%d request %d OMP_CANCELLATION=%d\n",
141 gtid, cncl_kind, __kmp_omp_cancellation));
142
143 KMP_DEBUG_ASSERT(cncl_kind != cancel_noreq);
144 KMP_DEBUG_ASSERT(cncl_kind == cancel_parallel || cncl_kind == cancel_loop ||
145 cncl_kind == cancel_sections ||
146 cncl_kind == cancel_taskgroup);
147 KMP_DEBUG_ASSERT(__kmp_get_gtid() == gtid);
148
149 if (__kmp_omp_cancellation) {
150 switch (cncl_kind) {
151 case cancel_parallel:
152 case cancel_loop:
153 case cancel_sections:
154 // cancellation requests for parallel and worksharing constructs
155 // are handled through the team structure
156 {
157 kmp_team_t *this_team = this_thr->th.th_team;
158 KMP_DEBUG_ASSERT(this_team);
159 if (this_team->t.t_cancel_request) {
160 if (cncl_kind == this_team->t.t_cancel_request) {
161// the request in the team structure matches the type of
162// cancellation point so we can cancel
163#if OMPT_SUPPORT && OMPT_OPTIONAL
164 if (ompt_enabled.ompt_callback_cancel) {
165 ompt_data_t *task_data;
166 __ompt_get_task_info_internal(ancestor_level: 0, NULL, task_data: &task_data, NULL, NULL,
167 NULL);
168 ompt_cancel_flag_t type = ompt_cancel_parallel;
169 if (cncl_kind == cancel_parallel)
170 type = ompt_cancel_parallel;
171 else if (cncl_kind == cancel_loop)
172 type = ompt_cancel_loop;
173 else if (cncl_kind == cancel_sections)
174 type = ompt_cancel_sections;
175 ompt_callbacks.ompt_callback(ompt_callback_cancel)(
176 task_data, type | ompt_cancel_detected,
177 OMPT_GET_RETURN_ADDRESS(0));
178 }
179#endif
180 return 1 /* true */;
181 }
182 KMP_ASSERT(0 /* false */);
183 } else {
184 // we do not have a cancellation request pending, so we just
185 // ignore this cancellation point
186 return 0;
187 }
188 break;
189 }
190 case cancel_taskgroup:
191 // cancellation requests for a task group
192 // are handled through the taskgroup structure
193 {
194 kmp_taskdata_t *task;
195 kmp_taskgroup_t *taskgroup;
196
197 task = this_thr->th.th_current_task;
198 KMP_DEBUG_ASSERT(task);
199
200 taskgroup = task->td_taskgroup;
201 if (taskgroup) {
202// return the current status of cancellation for the taskgroup
203#if OMPT_SUPPORT && OMPT_OPTIONAL
204 if (ompt_enabled.ompt_callback_cancel &&
205 !!taskgroup->cancel_request) {
206 ompt_data_t *task_data;
207 __ompt_get_task_info_internal(ancestor_level: 0, NULL, task_data: &task_data, NULL, NULL,
208 NULL);
209 ompt_callbacks.ompt_callback(ompt_callback_cancel)(
210 task_data, ompt_cancel_taskgroup | ompt_cancel_detected,
211 OMPT_GET_RETURN_ADDRESS(0));
212 }
213#endif
214 return !!taskgroup->cancel_request;
215 } else {
216 // if a cancellation point is encountered by a task that does not
217 // belong to a taskgroup, it is OK to ignore it
218 return 0 /* false */;
219 }
220 }
221 default:
222 KMP_ASSERT(0 /* false */);
223 }
224 }
225
226 // ICV OMP_CANCELLATION=false, so we ignore the cancellation point
227 KMP_DEBUG_ASSERT(!__kmp_omp_cancellation);
228 return 0 /* false */;
229}
230
231/*!
232@ingroup CANCELLATION
233@param loc_ref location of the original task directive
234@param gtid Global thread ID of encountering thread
235
236@return returns true if a matching cancellation request has been flagged in the
237RTL and the encountering thread has to cancel..
238
239Barrier with cancellation point to send threads from the barrier to the
240end of the parallel region. Needs a special code pattern as documented
241in the design document for the cancellation feature.
242*/
243kmp_int32 __kmpc_cancel_barrier(ident_t *loc, kmp_int32 gtid) {
244 int ret = 0 /* false */;
245 kmp_info_t *this_thr = __kmp_threads[gtid];
246 kmp_team_t *this_team = this_thr->th.th_team;
247
248 KMP_DEBUG_ASSERT(__kmp_get_gtid() == gtid);
249
250 // call into the standard barrier
251 __kmpc_barrier(loc, global_tid: gtid);
252
253 // if cancellation is active, check cancellation flag
254 if (__kmp_omp_cancellation) {
255 // depending on which construct to cancel, check the flag and
256 // reset the flag
257 switch (KMP_ATOMIC_LD_RLX(&(this_team->t.t_cancel_request))) {
258 case cancel_parallel:
259 ret = 1;
260 // ensure that threads have checked the flag, when
261 // leaving the above barrier
262 __kmpc_barrier(loc, global_tid: gtid);
263 this_team->t.t_cancel_request = cancel_noreq;
264 // the next barrier is the fork/join barrier, which
265 // synchronizes the threads leaving here
266 break;
267 case cancel_loop:
268 case cancel_sections:
269 ret = 1;
270 // ensure that threads have checked the flag, when
271 // leaving the above barrier
272 __kmpc_barrier(loc, global_tid: gtid);
273 this_team->t.t_cancel_request = cancel_noreq;
274 // synchronize the threads again to make sure we do not have any run-away
275 // threads that cause a race on the cancellation flag
276 __kmpc_barrier(loc, global_tid: gtid);
277 break;
278 case cancel_taskgroup:
279 // this case should not occur
280 KMP_ASSERT(0 /* false */);
281 break;
282 case cancel_noreq:
283 // do nothing
284 break;
285 default:
286 KMP_ASSERT(0 /* false */);
287 }
288 }
289
290 return ret;
291}
292
293/*!
294@ingroup CANCELLATION
295@param loc_ref location of the original task directive
296@param gtid Global thread ID of encountering thread
297
298@return returns true if a matching cancellation request has been flagged in the
299RTL and the encountering thread has to cancel..
300
301Query function to query the current status of cancellation requests.
302Can be used to implement the following pattern:
303
304if (kmp_get_cancellation_status(kmp_cancel_parallel)) {
305 perform_cleanup();
306 #pragma omp cancellation point parallel
307}
308*/
309int __kmp_get_cancellation_status(int cancel_kind) {
310 if (__kmp_omp_cancellation) {
311 kmp_info_t *this_thr = __kmp_entry_thread();
312
313 switch (cancel_kind) {
314 case cancel_parallel:
315 case cancel_loop:
316 case cancel_sections: {
317 kmp_team_t *this_team = this_thr->th.th_team;
318 return this_team->t.t_cancel_request == cancel_kind;
319 }
320 case cancel_taskgroup: {
321 kmp_taskdata_t *task;
322 kmp_taskgroup_t *taskgroup;
323 task = this_thr->th.th_current_task;
324 taskgroup = task->td_taskgroup;
325 return taskgroup && taskgroup->cancel_request;
326 }
327 }
328 }
329
330 return 0 /* false */;
331}
332

source code of openmp/runtime/src/kmp_cancel.cpp