src/simix/smx_network.cpp

   1 /* Copyright (c) 2009-2019. The SimGrid Team. All rights reserved.          */
   2
   3 /* This program is free software; you can redistribute it and/or modify it
   4  * under the terms of the license (GNU LGPL) which comes with this package. */
   5
   6 #include "mc/mc.h"
   7 #include "simgrid/Exception.hpp"
   8 #include "src/kernel/activity/MailboxImpl.hpp"
   9 #include "src/mc/mc_replay.hpp"
  10 #include "src/simix/smx_private.hpp"
  11 #include "src/surf/cpu_interface.hpp"
  12 #include "src/surf/network_interface.hpp"
  13
  14 #include <boost/range/algorithm.hpp>
  15
  16 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_network, simix, "SIMIX network-related synchronization");
  17
  18 static void SIMIX_waitany_remove_simcall_from_actions(smx_simcall_t simcall);
  19
  20 /******************************************************************************/
  21 /*                          Communication synchros                            */
  22 /******************************************************************************/
  23 XBT_PRIVATE void simcall_HANDLER_comm_send(smx_simcall_t simcall, smx_actor_t src, smx_mailbox_t mbox, double task_size,
  24                                            double rate, void* src_buff, size_t src_buff_size,
  25                                            int (*match_fun)(void*, void*, simgrid::kernel::activity::CommImpl*),
  26                                            void (*copy_data_fun)(smx_activity_t, void*, size_t), void* data,
  27                                            double timeout)
  28 {
  29   smx_activity_t comm = simcall_HANDLER_comm_isend(simcall, src, mbox, task_size, rate,
  30                            src_buff, src_buff_size, match_fun, nullptr, copy_data_fun,
  31                data, 0);
  32   SIMCALL_SET_MC_VALUE(simcall, 0);
  33   simcall_HANDLER_comm_wait(simcall, comm, timeout);
  34 }
  35
  36 XBT_PRIVATE smx_activity_t simcall_HANDLER_comm_isend(
  37     smx_simcall_t /*simcall*/, smx_actor_t src_proc, smx_mailbox_t mbox, double task_size, double rate, void* src_buff,
  38     size_t src_buff_size, int (*match_fun)(void*, void*, simgrid::kernel::activity::CommImpl*),
  39     void (*clean_fun)(void*), // used to free the synchro in case of problem after a detached send
  40     void (*copy_data_fun)(smx_activity_t, void*, size_t), // used to copy data if not default one
  41     void* data, int detached)
  42 {
  43   XBT_DEBUG("send from mailbox %p", mbox);
  44
  45   /* Prepare a synchro describing us, so that it gets passed to the user-provided filter of other side */
  46   simgrid::kernel::activity::CommImplPtr this_comm =
  47       simgrid::kernel::activity::CommImplPtr(new simgrid::kernel::activity::CommImpl(SIMIX_COMM_SEND));
  48
  49   /* Look for communication synchro matching our needs. We also provide a description of
  50    * ourself so that the other side also gets a chance of choosing if it wants to match with us.
  51    *
  52    * If it is not found then push our communication into the rendez-vous point */
  53   simgrid::kernel::activity::CommImplPtr other_comm = mbox->find_matching_comm(
  54       SIMIX_COMM_RECEIVE, match_fun, data, this_comm, /*done*/ false, /*remove_matching*/ true);
  55
  56   if (not other_comm) {
  57     other_comm = std::move(this_comm);
  58
  59     if (mbox->permanent_receiver_ != nullptr) {
  60       //this mailbox is for small messages, which have to be sent right now
  61       other_comm->state_  = SIMIX_READY;
  62       other_comm->dst_actor_ = mbox->permanent_receiver_.get();
  63       mbox->done_comm_queue_.push_back(other_comm);
  64       XBT_DEBUG("pushing a message into the permanent receive list %p, comm %p", mbox, other_comm.get());
  65
  66     }else{
  67       mbox->push(other_comm);
  68     }
  69   } else {
  70     XBT_DEBUG("Receive already pushed");
  71
  72     other_comm->state_ = SIMIX_READY;
  73     other_comm->type = SIMIX_COMM_READY;
  74   }
  75   src_proc->comms.push_back(other_comm);
  76
  77   if (detached) {
  78     other_comm->detached = true;
  79     other_comm->clean_fun = clean_fun;
  80   } else {
  81     other_comm->clean_fun = nullptr;
  82   }
  83
  84   /* Setup the communication synchro */
  85   other_comm->src_actor_     = src_proc;
  86   other_comm->task_size_     = task_size;
  87   other_comm->rate_          = rate;
  88   other_comm->src_buff_      = src_buff;
  89   other_comm->src_buff_size_ = src_buff_size;
  90   other_comm->src_data_      = data;
  91
  92   other_comm->match_fun = match_fun;
  93   other_comm->copy_data_fun = copy_data_fun;
  94
  95
  96   if (MC_is_active() || MC_record_replay_is_active()) {
  97     other_comm->state_ = SIMIX_RUNNING;
  98     return (detached ? nullptr : other_comm);
  99   }
 100
 101   other_comm->start();
 102
 103   return (detached ? nullptr : other_comm);
 104 }
 105
 106 XBT_PRIVATE void simcall_HANDLER_comm_recv(smx_simcall_t simcall, smx_actor_t receiver, smx_mailbox_t mbox,
 107                                            void* dst_buff, size_t* dst_buff_size,
 108                                            int (*match_fun)(void*, void*, simgrid::kernel::activity::CommImpl*),
 109                                            void (*copy_data_fun)(smx_activity_t, void*, size_t), void* data,
 110                                            double timeout, double rate)
 111 {
 112   smx_activity_t comm = simcall_HANDLER_comm_irecv(simcall, receiver, mbox, dst_buff, dst_buff_size, match_fun,
 113                                                    copy_data_fun, data, rate);
 114   SIMCALL_SET_MC_VALUE(simcall, 0);
 115   simcall_HANDLER_comm_wait(simcall, comm, timeout);
 116 }
 117
 118 XBT_PRIVATE smx_activity_t simcall_HANDLER_comm_irecv(smx_simcall_t /*simcall*/, smx_actor_t receiver,
 119                                                       smx_mailbox_t mbox, void* dst_buff, size_t* dst_buff_size,
 120                                                       simix_match_func_t match_fun,
 121                                                       void (*copy_data_fun)(smx_activity_t, void*, size_t), void* data,
 122                                                       double rate)
 123 {
 124   simgrid::kernel::activity::CommImplPtr this_synchro =
 125       simgrid::kernel::activity::CommImplPtr(new simgrid::kernel::activity::CommImpl(SIMIX_COMM_RECEIVE));
 126   XBT_DEBUG("recv from mbox %p. this_synchro=%p", mbox, this_synchro.get());
 127
 128   simgrid::kernel::activity::CommImplPtr other_comm;
 129   //communication already done, get it inside the list of completed comms
 130   if (mbox->permanent_receiver_ != nullptr && not mbox->done_comm_queue_.empty()) {
 131
 132     XBT_DEBUG("We have a comm that has probably already been received, trying to match it, to skip the communication");
 133     //find a match in the list of already received comms
 134     other_comm = mbox->find_matching_comm(SIMIX_COMM_SEND, match_fun, data, this_synchro, /*done*/ true,
 135                                           /*remove_matching*/ true);
 136     //if not found, assume the receiver came first, register it to the mailbox in the classical way
 137     if (not other_comm) {
 138       XBT_DEBUG("We have messages in the permanent receive list, but not the one we are looking for, pushing request into list");
 139       other_comm = std::move(this_synchro);
 140       mbox->push(other_comm);
 141     } else {
 142       if (other_comm->surf_action_ && other_comm->remains() < 1e-12) {
 143         XBT_DEBUG("comm %p has been already sent, and is finished, destroy it", other_comm.get());
 144         other_comm->state_ = SIMIX_DONE;
 145         other_comm->type = SIMIX_COMM_DONE;
 146         other_comm->mbox = nullptr;
 147       }
 148     }
 149   } else {
 150     /* Prepare a comm describing us, so that it gets passed to the user-provided filter of other side */
 151
 152     /* Look for communication activity matching our needs. We also provide a description of
 153      * ourself so that the other side also gets a chance of choosing if it wants to match with us.
 154      *
 155      * If it is not found then push our communication into the rendez-vous point */
 156     other_comm = mbox->find_matching_comm(SIMIX_COMM_SEND, match_fun, data, this_synchro, /*done*/ false,
 157                                           /*remove_matching*/ true);
 158
 159     if (other_comm == nullptr) {
 160       XBT_DEBUG("Receive pushed first (%zu comm enqueued so far)", mbox->comm_queue_.size());
 161       other_comm = std::move(this_synchro);
 162       mbox->push(other_comm);
 163     } else {
 164       XBT_DEBUG("Match my %p with the existing %p", this_synchro.get(), other_comm.get());
 165
 166       other_comm->state_ = SIMIX_READY;
 167       other_comm->type = SIMIX_COMM_READY;
 168     }
 169     receiver->comms.push_back(other_comm);
 170   }
 171
 172   /* Setup communication synchro */
 173   other_comm->dst_actor_     = receiver;
 174   other_comm->dst_buff_      = dst_buff;
 175   other_comm->dst_buff_size_ = dst_buff_size;
 176   other_comm->dst_data_      = data;
 177
 178   if (rate > -1.0 && (other_comm->rate_ < 0.0 || rate < other_comm->rate_))
 179     other_comm->rate_ = rate;
 180
 181   other_comm->match_fun = match_fun;
 182   other_comm->copy_data_fun = copy_data_fun;
 183
 184   if (MC_is_active() || MC_record_replay_is_active()) {
 185     other_comm->state_ = SIMIX_RUNNING;
 186     return other_comm;
 187   }
 188   other_comm->start();
 189   return other_comm;
 190 }
 191
 192 void simcall_HANDLER_comm_wait(smx_simcall_t simcall, smx_activity_t synchro, double timeout)
 193 {
 194   /* Associate this simcall to the wait synchro */
 195   XBT_DEBUG("simcall_HANDLER_comm_wait, %p", synchro.get());
 196
 197   synchro->simcalls_.push_back(simcall);
 198   simcall->issuer->waiting_synchro = synchro;
 199
 200   if (MC_is_active() || MC_record_replay_is_active()) {
 201     int idx = SIMCALL_GET_MC_VALUE(simcall);
 202     if (idx == 0) {
 203       synchro->state_ = SIMIX_DONE;
 204     } else {
 205       /* If we reached this point, the wait simcall must have a timeout */
 206       /* Otherwise it shouldn't be enabled and executed by the MC */
 207       if (timeout < 0.0)
 208         THROW_IMPOSSIBLE;
 209
 210       simgrid::kernel::activity::CommImplPtr comm =
 211           boost::static_pointer_cast<simgrid::kernel::activity::CommImpl>(synchro);
 212       if (comm->src_actor_ == simcall->issuer)
 213         comm->state_ = SIMIX_SRC_TIMEOUT;
 214       else
 215         comm->state_ = SIMIX_DST_TIMEOUT;
 216     }
 217
 218     SIMIX_comm_finish(synchro);
 219     return;
 220   }
 221
 222   /* If the synchro has already finish perform the error handling, */
 223   /* otherwise set up a waiting timeout on the right side          */
 224   if (synchro->state_ != SIMIX_WAITING && synchro->state_ != SIMIX_RUNNING) {
 225     SIMIX_comm_finish(synchro);
 226   } else { /* we need a sleep action (even when there is no timeout) to be notified of host failures */
 227     simgrid::kernel::resource::Action* sleep = simcall->issuer->host_->pimpl_cpu->sleep(timeout);
 228     sleep->set_data(synchro.get());
 229
 230     simgrid::kernel::activity::CommImplPtr comm =
 231         boost::static_pointer_cast<simgrid::kernel::activity::CommImpl>(synchro);
 232     if (simcall->issuer == comm->src_actor_)
 233       comm->src_timeout_ = sleep;
 234     else
 235       comm->dst_timeout_ = sleep;
 236   }
 237 }
 238
 239 void simcall_HANDLER_comm_test(smx_simcall_t simcall, smx_activity_t synchro)
 240 {
 241   simgrid::kernel::activity::CommImplPtr comm =
 242       boost::static_pointer_cast<simgrid::kernel::activity::CommImpl>(synchro);
 243
 244   int res;
 245
 246   if (MC_is_active() || MC_record_replay_is_active()){
 247     res = comm->src_actor_ && comm->dst_actor_;
 248     if (res)
 249       synchro->state_ = SIMIX_DONE;
 250   } else {
 251     res = synchro->state_ != SIMIX_WAITING && synchro->state_ != SIMIX_RUNNING;
 252   }
 253
 254   simcall_comm_test__set__result(simcall, res);
 255   if (simcall_comm_test__get__result(simcall)) {
 256     synchro->simcalls_.push_back(simcall);
 257     SIMIX_comm_finish(synchro);
 258   } else {
 259     SIMIX_simcall_answer(simcall);
 260   }
 261 }
 262
 263 void simcall_HANDLER_comm_testany(smx_simcall_t simcall, simgrid::kernel::activity::ActivityImplPtr comms[],
 264                                   size_t count)
 265 {
 266   // The default result is -1 -- this means, "nothing is ready".
 267   // It can be changed below, but only if something matches.
 268   simcall_comm_testany__set__result(simcall, -1);
 269
 270   if (MC_is_active() || MC_record_replay_is_active()){
 271     int idx = SIMCALL_GET_MC_VALUE(simcall);
 272     if(idx == -1){
 273       SIMIX_simcall_answer(simcall);
 274     }else{
 275       simgrid::kernel::activity::ActivityImplPtr synchro = comms[idx];
 276       simcall_comm_testany__set__result(simcall, idx);
 277       synchro->simcalls_.push_back(simcall);
 278       synchro->state_ = SIMIX_DONE;
 279       SIMIX_comm_finish(synchro);
 280     }
 281     return;
 282   }
 283
 284   for (std::size_t i = 0; i != count; ++i) {
 285     simgrid::kernel::activity::ActivityImplPtr synchro = comms[i];
 286     if (synchro->state_ != SIMIX_WAITING && synchro->state_ != SIMIX_RUNNING) {
 287       simcall_comm_testany__set__result(simcall, i);
 288       synchro->simcalls_.push_back(simcall);
 289       SIMIX_comm_finish(synchro);
 290       return;
 291     }
 292   }
 293   SIMIX_simcall_answer(simcall);
 294 }
 295
 296 void simcall_HANDLER_comm_waitany(smx_simcall_t simcall, xbt_dynar_t synchros, double timeout)
 297 {
 298   if (MC_is_active() || MC_record_replay_is_active()){
 299     if (timeout > 0.0)
 300       xbt_die("Timeout not implemented for waitany in the model-checker");
 301     int idx = SIMCALL_GET_MC_VALUE(simcall);
 302     smx_activity_t synchro = xbt_dynar_get_as(synchros, idx, smx_activity_t);
 303     synchro->simcalls_.push_back(simcall);
 304     simcall_comm_waitany__set__result(simcall, idx);
 305     synchro->state_ = SIMIX_DONE;
 306     SIMIX_comm_finish(synchro);
 307     return;
 308   }
 309
 310   if (timeout < 0.0){
 311     simcall->timer = NULL;
 312   } else {
 313     simcall->timer = SIMIX_timer_set(SIMIX_get_clock() + timeout, [simcall]() {
 314       SIMIX_waitany_remove_simcall_from_actions(simcall);
 315       simcall_comm_waitany__set__result(simcall, -1);
 316       SIMIX_simcall_answer(simcall);
 317     });
 318   }
 319
 320   unsigned int cursor;
 321   simgrid::kernel::activity::ActivityImpl* ptr;
 322   xbt_dynar_foreach(synchros, cursor, ptr){
 323     smx_activity_t synchro = simgrid::kernel::activity::ActivityImplPtr(ptr);
 324     /* associate this simcall to the the synchro */
 325     synchro->simcalls_.push_back(simcall);
 326
 327     /* see if the synchro is already finished */
 328     if (synchro->state_ != SIMIX_WAITING && synchro->state_ != SIMIX_RUNNING) {
 329       SIMIX_comm_finish(synchro);
 330       break;
 331     }
 332   }
 333 }
 334
 335 void SIMIX_waitany_remove_simcall_from_actions(smx_simcall_t simcall)
 336 {
 337   unsigned int cursor = 0;
 338   xbt_dynar_t synchros = simcall_comm_waitany__get__comms(simcall);
 339
 340   simgrid::kernel::activity::ActivityImpl* ptr;
 341   xbt_dynar_foreach(synchros, cursor, ptr){
 342     smx_activity_t synchro = simgrid::kernel::activity::ActivityImplPtr(ptr);
 343
 344     // Remove the first occurence of simcall:
 345     auto i = boost::range::find(synchro->simcalls_, simcall);
 346     if (i != synchro->simcalls_.end())
 347       synchro->simcalls_.erase(i);
 348   }
 349 }
 350
 351 /**
 352  * @brief Answers the SIMIX simcalls associated to a communication synchro.
 353  * @param synchro a finished communication synchro
 354  */
 355 void SIMIX_comm_finish(smx_activity_t synchro)
 356 {
 357   simgrid::kernel::activity::CommImplPtr comm =
 358       boost::static_pointer_cast<simgrid::kernel::activity::CommImpl>(synchro);
 359
 360   while (not synchro->simcalls_.empty()) {
 361     smx_simcall_t simcall = synchro->simcalls_.front();
 362     synchro->simcalls_.pop_front();
 363
 364     /* If a waitany simcall is waiting for this synchro to finish, then remove it from the other synchros in the waitany
 365      * list. Afterwards, get the position of the actual synchro in the waitany dynar and return it as the result of the
 366      * simcall */
 367
 368     if (simcall->call == SIMCALL_NONE) //FIXME: maybe a better way to handle this case
 369       continue; // if process handling comm is killed
 370     if (simcall->call == SIMCALL_COMM_WAITANY) {
 371       SIMIX_waitany_remove_simcall_from_actions(simcall);
 372       if (simcall->timer) {
 373         SIMIX_timer_remove(simcall->timer);
 374         simcall->timer = nullptr;
 375       }
 376       if (not MC_is_active() && not MC_record_replay_is_active())
 377         simcall_comm_waitany__set__result(simcall,
 378                                           xbt_dynar_search(simcall_comm_waitany__get__comms(simcall), &synchro));
 379     }
 380
 381     /* If the synchro is still in a rendez-vous point then remove from it */
 382     if (comm->mbox)
 383       comm->mbox->remove(comm);
 384
 385     XBT_DEBUG("SIMIX_comm_finish: synchro state = %d", (int)synchro->state_);
 386
 387     /* Check out for errors */
 388
 389     if (not simcall->issuer->host_->is_on()) {
 390       simcall->issuer->context_->iwannadie = true;
 391       simcall->issuer->exception =
 392           std::make_exception_ptr(simgrid::HostFailureException(XBT_THROW_POINT, "Host failed"));
 393     } else {
 394       switch (comm->state_) {
 395
 396         case SIMIX_DONE:
 397           XBT_DEBUG("Communication %p complete!", synchro.get());
 398           comm->copy_data();
 399           break;
 400
 401         case SIMIX_SRC_TIMEOUT:
 402           simcall->issuer->exception = std::make_exception_ptr(
 403               simgrid::TimeoutError(XBT_THROW_POINT, "Communication timeouted because of the sender"));
 404           break;
 405
 406         case SIMIX_DST_TIMEOUT:
 407           simcall->issuer->exception = std::make_exception_ptr(
 408               simgrid::TimeoutError(XBT_THROW_POINT, "Communication timeouted because of the receiver"));
 409           break;
 410
 411         case SIMIX_SRC_HOST_FAILURE:
 412           if (simcall->issuer == comm->src_actor_)
 413             simcall->issuer->context_->iwannadie = true;
 414           else
 415             simcall->issuer->exception =
 416                 std::make_exception_ptr(simgrid::NetworkFailureException(XBT_THROW_POINT, "Remote peer failed"));
 417           break;
 418
 419         case SIMIX_DST_HOST_FAILURE:
 420           if (simcall->issuer == comm->dst_actor_)
 421             simcall->issuer->context_->iwannadie = true;
 422           else
 423             simcall->issuer->exception =
 424                 std::make_exception_ptr(simgrid::NetworkFailureException(XBT_THROW_POINT, "Remote peer failed"));
 425           break;
 426
 427         case SIMIX_LINK_FAILURE:
 428           XBT_DEBUG("Link failure in synchro %p between '%s' and '%s': posting an exception to the issuer: %s (%p) "
 429                     "detached:%d",
 430                     synchro.get(), comm->src_actor_ ? comm->src_actor_->host_->get_cname() : nullptr,
 431                     comm->dst_actor_ ? comm->dst_actor_->host_->get_cname() : nullptr, simcall->issuer->get_cname(),
 432                     simcall->issuer, comm->detached);
 433           if (comm->src_actor_ == simcall->issuer) {
 434             XBT_DEBUG("I'm source");
 435           } else if (comm->dst_actor_ == simcall->issuer) {
 436             XBT_DEBUG("I'm dest");
 437           } else {
 438             XBT_DEBUG("I'm neither source nor dest");
 439           }
 440           simcall->issuer->throw_exception(
 441               std::make_exception_ptr(simgrid::NetworkFailureException(XBT_THROW_POINT, "Link failure")));
 442           break;
 443
 444         case SIMIX_CANCELED:
 445           if (simcall->issuer == comm->dst_actor_)
 446             SMX_EXCEPTION(simcall->issuer, cancel_error, 0, "Communication canceled by the sender");
 447           else
 448             SMX_EXCEPTION(simcall->issuer, cancel_error, 0, "Communication canceled by the receiver");
 449           break;
 450
 451         default:
 452           xbt_die("Unexpected synchro state in SIMIX_comm_finish: %d", (int)synchro->state_);
 453       }
 454     }
 455
 456     /* if there is an exception during a waitany or a testany, indicate the position of the failed communication */
 457     if (simcall->issuer->exception &&
 458         (simcall->call == SIMCALL_COMM_WAITANY || simcall->call == SIMCALL_COMM_TESTANY)) {
 459       // First retrieve the rank of our failing synchro
 460       int rank = -1;
 461       if (simcall->call == SIMCALL_COMM_WAITANY) {
 462         rank = xbt_dynar_search(simcall_comm_waitany__get__comms(simcall), &synchro);
 463       } else if (simcall->call == SIMCALL_COMM_TESTANY) {
 464         rank         = -1;
 465         auto* comms  = simcall_comm_testany__get__comms(simcall);
 466         auto count   = simcall_comm_testany__get__count(simcall);
 467         auto element = std::find(comms, comms + count, synchro);
 468         if (element == comms + count)
 469           rank = -1;
 470         else
 471           rank = element - comms;
 472       }
 473
 474       // In order to modify the exception we have to rethrow it:
 475       try {
 476         std::rethrow_exception(simcall->issuer->exception);
 477       } catch (simgrid::TimeoutError& e) {
 478         e.value                    = rank;
 479         simcall->issuer->exception = std::make_exception_ptr(e);
 480       } catch (simgrid::NetworkFailureException& e) {
 481         e.value                    = rank;
 482         simcall->issuer->exception = std::make_exception_ptr(e);
 483       } catch (xbt_ex& e) {
 484         if (e.category == cancel_error) {
 485           e.value                    = rank;
 486           simcall->issuer->exception = std::make_exception_ptr(e);
 487         } else {
 488           xbt_die("Unexpected xbt_ex(%s). Please enhance this code", xbt_ex_catname(e.category));
 489         }
 490       }
 491     }
 492
 493     simcall->issuer->waiting_synchro = nullptr;
 494     simcall->issuer->comms.remove(synchro);
 495     if(comm->detached){
 496       if (simcall->issuer == comm->src_actor_) {
 497         if (comm->dst_actor_)
 498           comm->dst_actor_->comms.remove(synchro);
 499       } else if (simcall->issuer == comm->dst_actor_) {
 500         if (comm->src_actor_)
 501           comm->src_actor_->comms.remove(synchro);
 502       }
 503       else{
 504         comm->dst_actor_->comms.remove(synchro);
 505         comm->src_actor_->comms.remove(synchro);
 506       }
 507     }
 508
 509     if (simcall->issuer->host_->is_on())
 510       SIMIX_simcall_answer(simcall);
 511     else
 512       simcall->issuer->context_->iwannadie = true;
 513   }
 514 }
 515
 516 void SIMIX_comm_copy_buffer_callback(smx_activity_t synchro, void* buff, size_t buff_size)
 517 {
 518   simgrid::kernel::activity::CommImplPtr comm =
 519       boost::static_pointer_cast<simgrid::kernel::activity::CommImpl>(synchro);
 520
 521   XBT_DEBUG("Copy the data over");
 522   memcpy(comm->dst_buff_, buff, buff_size);
 523   if (comm->detached) { // if this is a detached send, the source buffer was duplicated by SMPI sender to make the original buffer available to the application ASAP
 524     xbt_free(buff);
 525     comm->src_buff_ = nullptr;
 526   }
 527 }