1 /* Copyright (c) 2009, 2010. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
12 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_network, simix,
13 "Logging specific to SIMIX (network)");
15 static xbt_dict_t rdv_points = NULL;
16 unsigned long int smx_total_comms = 0;
18 static XBT_INLINE void SIMIX_comm_start(smx_action_t action);
19 static void SIMIX_comm_finish(smx_action_t action);
20 static void SIMIX_waitany_req_remove_from_actions(smx_req_t req);
21 static void SIMIX_comm_copy_data(smx_action_t comm);
22 static smx_action_t SIMIX_comm_new(e_smx_comm_type_t type);
23 static XBT_INLINE void SIMIX_rdv_push(smx_rdv_t rdv, smx_action_t comm);
24 static XBT_INLINE void SIMIX_rdv_remove(smx_rdv_t rdv, smx_action_t comm);
25 static smx_action_t SIMIX_rdv_get_request(smx_rdv_t rdv, e_smx_comm_type_t type,
26 int (*match_fun)(void *, void *), void *);
27 static void SIMIX_rdv_free(void *data);
29 void SIMIX_network_init(void)
31 rdv_points = xbt_dict_new();
34 void SIMIX_network_exit(void)
36 xbt_dict_free(&rdv_points);
39 /******************************************************************************/
40 /* Rendez-Vous Points */
41 /******************************************************************************/
43 smx_rdv_t SIMIX_rdv_create(const char *name)
45 /* two processes may have pushed the same rdv_create request at the same time */
46 smx_rdv_t rdv = name ? xbt_dict_get_or_null(rdv_points, name) : NULL;
49 rdv = xbt_new0(s_smx_rvpoint_t, 1);
50 rdv->name = name ? xbt_strdup(name) : NULL;
51 rdv->comm_fifo = xbt_fifo_new();
54 xbt_dict_set(rdv_points, rdv->name, rdv, SIMIX_rdv_free);
59 void SIMIX_rdv_destroy(smx_rdv_t rdv)
62 xbt_dict_remove(rdv_points, rdv->name);
65 void SIMIX_rdv_free(void *data)
67 smx_rdv_t rdv = (smx_rdv_t) data;
70 xbt_fifo_free(rdv->comm_fifo);
74 smx_rdv_t SIMIX_rdv_get_by_name(const char *name)
76 return xbt_dict_get_or_null(rdv_points, name);
79 int SIMIX_rdv_comm_count_by_host(smx_rdv_t rdv, smx_host_t host)
81 smx_action_t comm = NULL;
82 xbt_fifo_item_t item = NULL;
85 xbt_fifo_foreach(rdv->comm_fifo, item, comm, smx_action_t) {
86 if (comm->comm.src_proc->smx_host == host)
93 smx_action_t SIMIX_rdv_get_head(smx_rdv_t rdv)
95 return xbt_fifo_get_item_content(xbt_fifo_get_first_item(rdv->comm_fifo));
99 * \brief Push a communication request into a rendez-vous point
100 * \param rdv The rendez-vous point
101 * \param comm The communication request
103 static XBT_INLINE void SIMIX_rdv_push(smx_rdv_t rdv, smx_action_t comm)
105 xbt_fifo_push(rdv->comm_fifo, comm);
106 comm->comm.rdv = rdv;
110 * \brief Remove a communication request from a rendez-vous point
111 * \param rdv The rendez-vous point
112 * \param comm The communication request
114 static XBT_INLINE void SIMIX_rdv_remove(smx_rdv_t rdv, smx_action_t comm)
116 xbt_fifo_remove(rdv->comm_fifo, comm);
117 comm->comm.rdv = NULL;
120 smx_action_t SIMIX_comm_get_send_match(smx_rdv_t rdv, int (*match_fun)(void*, void*), void* data) {
121 return SIMIX_rdv_get_request(rdv, SIMIX_COMM_SEND, match_fun, data);
125 * \brief Checks if there is a communication action queued in a rendez-vous matching our needs
126 * \param type The type of communication we are looking for (comm_send, comm_recv)
127 * \return The communication action if found, NULL otherwise
129 smx_action_t SIMIX_rdv_get_request(smx_rdv_t rdv, e_smx_comm_type_t type,
130 int (*match_fun)(void *, void *), void *data)
133 xbt_fifo_item_t item;
134 void* req_data = NULL;
136 xbt_fifo_foreach(rdv->comm_fifo, item, action, smx_action_t){
137 if (action->comm.type == SIMIX_COMM_SEND) {
138 req_data = action->comm.src_data;
139 } else if (action->comm.type == SIMIX_COMM_RECEIVE) {
140 req_data = action->comm.dst_data;
142 if (action->comm.type == type && (!match_fun || match_fun(data, req_data))) {
143 XBT_DEBUG("Found a matching communication action %p", action);
144 xbt_fifo_remove_item(rdv->comm_fifo, item);
145 xbt_fifo_free_item(item);
146 action->comm.refcount++;
147 action->comm.rdv = NULL;
150 XBT_DEBUG("Sorry, communication action %p does not match our needs:"
151 " its type is %d but we are looking for a comm of type %d",
152 action, action->comm.type, type);
154 XBT_DEBUG("No matching communication action found");
158 /******************************************************************************/
159 /* Comunication Actions */
160 /******************************************************************************/
163 * \brief Creates a new comunicate action
164 * \param type The type of request (comm_send, comm_recv)
165 * \return The new comunicate action
167 smx_action_t SIMIX_comm_new(e_smx_comm_type_t type)
171 /* alloc structures */
172 act = xbt_mallocator_get(simix_global->action_mallocator);
173 act->type = SIMIX_ACTION_COMMUNICATE;
174 act->state = SIMIX_WAITING;
176 /* set communication */
177 act->comm.type = type;
178 act->comm.refcount = 1;
180 #ifdef HAVE_LATENCY_BOUND_TRACKING
181 //initialize with unknown value
182 act->latency_limited = -1;
186 act->category = NULL;
189 XBT_DEBUG("Create communicate action %p", act);
196 * \brief Destroy a communicate action
197 * \param action The communicate action to be destroyed
199 void SIMIX_comm_destroy(smx_action_t action)
201 XBT_DEBUG("Destroy action %p (refcount:%d)", action, action->comm.refcount);
203 if (action->comm.refcount <= 0)
204 xbt_die("the refcount of comm %p is already 0 before decreasing it. "
205 "That's a bug!", action);
207 action->comm.refcount--;
208 if (action->comm.refcount > 0)
210 XBT_DEBUG("Really free communication %p; refcount is now %d", action,
211 action->comm.refcount);
213 #ifdef HAVE_LATENCY_BOUND_TRACKING
214 action->latency_limited = SIMIX_comm_is_latency_bounded( action ) ;
218 TRACE_smx_action_destroy(action);
221 xbt_free(action->name);
222 SIMIX_comm_destroy_internal_actions(action);
224 if (action->comm.detached && action->state != SIMIX_DONE) {
225 /* the communication has failed and was detached:
226 * we have to free the buffer */
227 ((void_f_pvoid_t) action->comm.src_data)(action->comm.src_buff);
230 xbt_mallocator_release(simix_global->action_mallocator, action);
233 void SIMIX_comm_destroy_internal_actions(smx_action_t action)
235 if (action->comm.surf_comm){
236 #ifdef HAVE_LATENCY_BOUND_TRACKING
237 action->latency_limited = SIMIX_comm_is_latency_bounded(action);
239 action->comm.surf_comm->model_type->action_unref(action->comm.surf_comm);
240 action->comm.surf_comm = NULL;
243 if (action->comm.src_timeout){
244 action->comm.src_timeout->model_type->action_unref(action->comm.src_timeout);
245 action->comm.src_timeout = NULL;
248 if (action->comm.dst_timeout){
249 action->comm.dst_timeout->model_type->action_unref(action->comm.dst_timeout);
250 action->comm.dst_timeout = NULL;
254 smx_action_t SIMIX_comm_isend(smx_process_t src_proc, smx_rdv_t rdv,
255 double task_size, double rate,
256 void *src_buff, size_t src_buff_size,
257 int (*match_fun)(void *, void *), void *data,
262 /* Look for communication request matching our needs.
263 If it is not found then create it and push it into the rendez-vous point */
264 action = SIMIX_rdv_get_request(rdv, SIMIX_COMM_RECEIVE, match_fun, data);
267 action = SIMIX_comm_new(SIMIX_COMM_SEND);
268 SIMIX_rdv_push(rdv, action);
270 action->state = SIMIX_READY;
271 action->comm.type = SIMIX_COMM_READY;
274 /* If the communication action is detached then decrease the refcount
275 * by one, so it will be eliminated by the receivers destroy call */
277 action->comm.detached = 1;
278 action->comm.refcount--;
281 /* Setup the communication request */
282 action->comm.src_proc = src_proc;
283 action->comm.task_size = task_size;
284 action->comm.rate = rate;
285 action->comm.src_buff = src_buff;
286 action->comm.src_buff_size = src_buff_size;
287 action->comm.src_data = data;
290 action->state = SIMIX_RUNNING;
294 SIMIX_comm_start(action);
298 smx_action_t SIMIX_comm_irecv(smx_process_t dst_proc, smx_rdv_t rdv,
299 void *dst_buff, size_t *dst_buff_size,
300 int (*match_fun)(void *, void *), void *data)
304 /* Look for communication request matching our needs.
305 * If it is not found then create it and push it into the rendez-vous point
307 action = SIMIX_rdv_get_request(rdv, SIMIX_COMM_SEND, match_fun, data);
310 action = SIMIX_comm_new(SIMIX_COMM_RECEIVE);
311 SIMIX_rdv_push(rdv, action);
313 action->state = SIMIX_READY;
314 action->comm.type = SIMIX_COMM_READY;
317 /* Setup communication request */
318 action->comm.dst_proc = dst_proc;
319 action->comm.dst_buff = dst_buff;
320 action->comm.dst_buff_size = dst_buff_size;
321 action->comm.dst_data = data;
324 action->state = SIMIX_RUNNING;
328 SIMIX_comm_start(action);
332 void SIMIX_pre_comm_wait(smx_req_t req, smx_action_t action, double timeout, int idx)
334 /* the request may be a wait, a send or a recv */
337 /* Associate this request to the action */
338 xbt_fifo_push(action->request_list, req);
339 req->issuer->waiting_action = action;
343 action->state = SIMIX_DONE;
345 /* If we reached this point, the wait request must have a timeout */
346 /* Otherwise it shouldn't be enabled and executed by the MC */
350 if (action->comm.src_proc == req->issuer)
351 action->state = SIMIX_SRC_TIMEOUT;
353 action->state = SIMIX_DST_TIMEOUT;
356 SIMIX_comm_finish(action);
360 /* If the action has already finish perform the error handling, */
361 /* otherwise set up a waiting timeout on the right side */
362 if (action->state != SIMIX_WAITING && action->state != SIMIX_RUNNING) {
363 SIMIX_comm_finish(action);
364 } else { /* if (timeout >= 0) { we need a surf sleep action even when there is no timeout, otherwise surf won't tell us when the host fails */
365 sleep = surf_workstation_model->extension.workstation.sleep(req->issuer->smx_host->host, timeout);
366 surf_workstation_model->action_data_set(sleep, action);
368 if (req->issuer == action->comm.src_proc)
369 action->comm.src_timeout = sleep;
371 action->comm.dst_timeout = sleep;
375 void SIMIX_pre_comm_test(smx_req_t req)
377 smx_action_t action = req->comm_test.comm;
380 req->comm_test.result = action->comm.src_proc && action->comm.dst_proc;
381 if(req->comm_test.result){
382 action->state = SIMIX_DONE;
383 xbt_fifo_push(action->request_list, req);
384 SIMIX_comm_finish(action);
386 SIMIX_request_answer(req);
391 req->comm_test.result = (action->state != SIMIX_WAITING && action->state != SIMIX_RUNNING);
392 if (req->comm_test.result) {
393 xbt_fifo_push(action->request_list, req);
394 SIMIX_comm_finish(action);
396 SIMIX_request_answer(req);
400 void SIMIX_pre_comm_testany(smx_req_t req, int idx)
404 xbt_dynar_t actions = req->comm_testany.comms;
405 req->comm_testany.result = -1;
409 SIMIX_request_answer(req);
411 action = xbt_dynar_get_as(actions, idx, smx_action_t);
412 req->comm_testany.result = idx;
413 xbt_fifo_push(action->request_list, req);
414 action->state = SIMIX_DONE;
415 SIMIX_comm_finish(action);
420 xbt_dynar_foreach(req->comm_testany.comms,cursor,action) {
421 if (action->state != SIMIX_WAITING && action->state != SIMIX_RUNNING) {
422 req->comm_testany.result = cursor;
423 xbt_fifo_push(action->request_list, req);
424 SIMIX_comm_finish(action);
428 SIMIX_request_answer(req);
431 void SIMIX_pre_comm_waitany(smx_req_t req, int idx)
434 unsigned int cursor = 0;
435 xbt_dynar_t actions = req->comm_waitany.comms;
438 action = xbt_dynar_get_as(actions, idx, smx_action_t);
439 xbt_fifo_push(action->request_list, req);
440 req->comm_waitany.result = idx;
441 action->state = SIMIX_DONE;
442 SIMIX_comm_finish(action);
446 xbt_dynar_foreach(actions, cursor, action){
447 /* Associate this request to the action */
448 xbt_fifo_push(action->request_list, req);
449 if (action->state != SIMIX_WAITING && action->state != SIMIX_RUNNING){
450 SIMIX_comm_finish(action);
456 void SIMIX_waitany_req_remove_from_actions(smx_req_t req)
459 unsigned int cursor = 0;
460 xbt_dynar_t actions = req->comm_waitany.comms;
462 xbt_dynar_foreach(actions, cursor, action){
463 xbt_fifo_remove(action->request_list, req);
468 * \brief Start the simulation of a communication request
469 * \param action The communication action
471 static XBT_INLINE void SIMIX_comm_start(smx_action_t action)
473 /* If both the sender and the receiver are already there, start the communication */
474 if (action->state == SIMIX_READY) {
475 smx_host_t sender = action->comm.src_proc->smx_host;
476 smx_host_t receiver = action->comm.dst_proc->smx_host;
478 XBT_DEBUG("Starting communication %p from '%s' to '%s'", action,
479 SIMIX_host_get_name(sender), SIMIX_host_get_name(receiver));
481 action->comm.surf_comm = surf_workstation_model->extension.workstation.
482 communicate(sender->host, receiver->host, action->comm.task_size, action->comm.rate);
484 surf_workstation_model->action_data_set(action->comm.surf_comm, action);
486 action->state = SIMIX_RUNNING;
489 TRACE_smx_action_communicate(action, action->comm.src_proc);
492 /* If a link is failed, detect it immediately */
493 if (surf_workstation_model->action_state_get(action->comm.surf_comm) == SURF_ACTION_FAILED) {
494 XBT_DEBUG("Communication from '%s' to '%s' failed to start because of a link failure",
495 SIMIX_host_get_name(sender), SIMIX_host_get_name(receiver));
496 action->state = SIMIX_LINK_FAILURE;
497 SIMIX_comm_destroy_internal_actions(action);
500 /* If any of the process is suspend, create the action but stop its execution,
501 it will be restarted when the sender process resume */
502 if (SIMIX_process_is_suspended(action->comm.src_proc) ||
503 SIMIX_process_is_suspended(action->comm.dst_proc)) {
504 /* FIXME: check what should happen with the action state */
505 surf_workstation_model->suspend(action->comm.surf_comm);
510 void SIMIX_comm_finish(smx_action_t action)
512 unsigned int destroy_count = 0;
515 while ((req = xbt_fifo_shift(action->request_list))) {
517 /* If a waitany request is waiting for this action to finish, then remove
518 it from the other actions in the waitany list. Afterwards, get the
519 position of the actual action in the waitany request's actions dynar and
520 return it as the result of the call */
521 if (req->call == REQ_COMM_WAITANY) {
522 SIMIX_waitany_req_remove_from_actions(req);
524 req->comm_waitany.result = xbt_dynar_search(req->comm_waitany.comms, &action);
527 /* If the action is still in a rendez-vous point then remove from it */
528 if (action->comm.rdv)
529 SIMIX_rdv_remove(action->comm.rdv, action);
531 XBT_DEBUG("SIMIX_comm_finish: action state = %d", action->state);
533 /* Check out for errors */
534 switch (action->state) {
537 XBT_DEBUG("Communication %p complete!", action);
538 SIMIX_comm_copy_data(action);
541 case SIMIX_SRC_TIMEOUT:
543 THROW0(timeout_error, 0, "Communication timeouted because of sender");
545 CATCH(req->issuer->running_ctx->exception) {
546 req->issuer->doexception = 1;
550 case SIMIX_DST_TIMEOUT:
552 THROW0(timeout_error, 0, "Communication timeouted because of receiver");
554 CATCH(req->issuer->running_ctx->exception) {
555 req->issuer->doexception = 1;
559 case SIMIX_SRC_HOST_FAILURE:
561 if (req->issuer == action->comm.src_proc)
562 THROW0(host_error, 0, "Host failed");
564 THROW0(network_error, 0, "Remote peer failed");
566 CATCH(req->issuer->running_ctx->exception) {
567 req->issuer->doexception = 1;
571 case SIMIX_DST_HOST_FAILURE:
573 if (req->issuer == action->comm.dst_proc)
574 THROW0(host_error, 0, "Host failed");
576 THROW0(network_error, 0, "Remote peer failed");
578 CATCH(req->issuer->running_ctx->exception) {
579 req->issuer->doexception = 1;
583 case SIMIX_LINK_FAILURE:
585 XBT_DEBUG("Link failure in action %p between '%s' and '%s': posting an exception to the issuer: %s (%p)",
586 action, action->comm.src_proc->smx_host->name, action->comm.dst_proc->smx_host->name,
587 req->issuer->name, req->issuer);
588 THROW0(network_error, 0, "Link failure");
590 CATCH(req->issuer->running_ctx->exception) {
591 req->issuer->doexception = 1;
599 /* if there is an exception during a waitany or a testany, indicate the position of the failed communication */
600 if (req->issuer->doexception) {
601 if (req->call == REQ_COMM_WAITANY) {
602 req->issuer->running_ctx->exception.value = xbt_dynar_search(req->comm_waitany.comms, &action);
604 else if (req->call == REQ_COMM_TESTANY) {
605 req->issuer->running_ctx->exception.value = xbt_dynar_search(req->comm_testany.comms, &action);
609 req->issuer->waiting_action = NULL;
610 SIMIX_request_answer(req);
614 while (destroy_count-- > 0)
615 SIMIX_comm_destroy(action);
618 void SIMIX_post_comm(smx_action_t action)
620 /* Update action state */
621 if (action->comm.src_timeout &&
622 surf_workstation_model->action_state_get(action->comm.src_timeout) == SURF_ACTION_DONE)
623 action->state = SIMIX_SRC_TIMEOUT;
624 else if (action->comm.dst_timeout &&
625 surf_workstation_model->action_state_get(action->comm.dst_timeout) == SURF_ACTION_DONE)
626 action->state = SIMIX_DST_TIMEOUT;
627 else if (action->comm.src_timeout &&
628 surf_workstation_model->action_state_get(action->comm.src_timeout) == SURF_ACTION_FAILED)
629 action->state = SIMIX_SRC_HOST_FAILURE;
630 else if (action->comm.dst_timeout &&
631 surf_workstation_model->action_state_get(action->comm.dst_timeout) == SURF_ACTION_FAILED)
632 action->state = SIMIX_DST_HOST_FAILURE;
633 else if (action->comm.surf_comm &&
634 surf_workstation_model->action_state_get(action->comm.surf_comm) == SURF_ACTION_FAILED)
635 action->state = SIMIX_LINK_FAILURE;
637 action->state = SIMIX_DONE;
639 XBT_DEBUG("SIMIX_post_comm: action state = %d", action->state);
641 /* After this point the surf actions associated with the simix communicate
642 action are no longer needed, thus we delete them. */
643 SIMIX_comm_destroy_internal_actions(action);
645 /* If there are requests associated with the action, then answer them */
646 if (xbt_fifo_size(action->request_list))
647 SIMIX_comm_finish(action);
650 void SIMIX_comm_cancel(smx_action_t action)
652 /* If the action is a waiting state means that it is still in a rdv */
653 /* so remove from it and delete it */
654 if (action->state == SIMIX_WAITING) {
655 SIMIX_rdv_remove(action->comm.rdv, action);
656 action->state = SIMIX_FAILED;
658 /* When running the MC there are no surf actions */
660 surf_workstation_model->action_cancel(action->comm.surf_comm);
664 void SIMIX_comm_suspend(smx_action_t action)
666 /*FIXME: shall we suspend also the timeout actions? */
667 surf_workstation_model->suspend(action->comm.surf_comm);
670 void SIMIX_comm_resume(smx_action_t action)
672 /*FIXME: check what happen with the timeouts */
673 surf_workstation_model->resume(action->comm.surf_comm);
677 /************* Action Getters **************/
680 * \brief get the amount remaining from the communication
681 * \param action The communication
683 double SIMIX_comm_get_remains(smx_action_t action)
687 switch (action->state) {
690 remains = surf_workstation_model->get_remains(action->comm.surf_comm);
695 remains = 0; /*FIXME: check what should be returned */
699 remains = 0; /*FIXME: is this correct? */
705 e_smx_state_t SIMIX_comm_get_state(smx_action_t action)
707 return action->state;
711 * \brief Return the user data associated to the sender of the communication
712 * \param action The communication
713 * \return the user data
715 void* SIMIX_comm_get_src_data(smx_action_t action)
717 return action->comm.src_data;
721 * \brief Return the user data associated to the receiver of the communication
722 * \param action The communication
723 * \return the user data
725 void* SIMIX_comm_get_dst_data(smx_action_t action)
727 return action->comm.dst_data;
730 smx_process_t SIMIX_comm_get_src_proc(smx_action_t action)
732 return action->comm.src_proc;
735 smx_process_t SIMIX_comm_get_dst_proc(smx_action_t action)
737 return action->comm.dst_proc;
740 #ifdef HAVE_LATENCY_BOUND_TRACKING
742 * \brief verify if communication is latency bounded
743 * \param comm The communication
745 XBT_INLINE int SIMIX_comm_is_latency_bounded(smx_action_t action)
747 if (action->comm.surf_comm){
748 XBT_DEBUG("Getting latency limited for surf_action (%p)", action->comm.surf_comm);
749 action->latency_limited = surf_workstation_model->get_latency_limited(action->comm.surf_comm);
750 XBT_DEBUG("Action limited is %d", action->latency_limited);
752 return action->latency_limited;
756 /******************************************************************************/
757 /* SIMIX_comm_copy_data callbacks */
758 /******************************************************************************/
759 static void (*SIMIX_comm_copy_data_callback) (smx_action_t, size_t) =
760 &SIMIX_comm_copy_pointer_callback;
763 SIMIX_comm_set_copy_data_callback(void (*callback) (smx_action_t, size_t))
765 SIMIX_comm_copy_data_callback = callback;
768 void SIMIX_comm_copy_pointer_callback(smx_action_t comm, size_t buff_size)
770 xbt_assert1((buff_size == sizeof(void *)),
771 "Cannot copy %zu bytes: must be sizeof(void*)", buff_size);
772 *(void **) (comm->comm.dst_buff) = comm->comm.src_buff;
775 void SIMIX_comm_copy_buffer_callback(smx_action_t comm, size_t buff_size)
777 memcpy(comm->comm.dst_buff, comm->comm.src_buff, buff_size);
781 * \brief Copy the communication data from the sender's buffer to the receiver's one
782 * \param comm The communication
784 void SIMIX_comm_copy_data(smx_action_t comm)
786 size_t buff_size = comm->comm.src_buff_size;
787 /* If there is no data to be copy then return */
788 if (!comm->comm.src_buff || !comm->comm.dst_buff || comm->comm.copied == 1)
791 XBT_DEBUG("Copying comm %p data from %s (%p) -> %s (%p) (%zu bytes)",
793 comm->comm.src_proc->smx_host->name, comm->comm.src_buff,
794 comm->comm.dst_proc->smx_host->name, comm->comm.dst_buff, buff_size);
796 /* Copy at most dst_buff_size bytes of the message to receiver's buffer */
797 if (comm->comm.dst_buff_size)
798 buff_size = MIN(buff_size, *(comm->comm.dst_buff_size));
800 /* Update the receiver's buffer size to the copied amount */
801 if (comm->comm.dst_buff_size)
802 *comm->comm.dst_buff_size = buff_size;
807 (*SIMIX_comm_copy_data_callback) (comm, buff_size);
809 /* Set the copied flag so we copy data only once */
810 /* (this function might be called from both communication ends) */
811 comm->comm.copied = 1;