1 /* This file deals with creating processes (via FORK) and deleting them (via 2 * EXIT/WAITPID). When a process forks, a new slot in the 'mproc' table is 3 * allocated for it, and a copy of the parent's core image is made for the 4 * child. Then the kernel and file system are informed. A process is removed 5 * from the 'mproc' table when two events have occurred: (1) it has exited or 6 * been killed by a signal, and (2) the parent has done a WAITPID. If the 7 * process exits first, it continues to occupy a slot until the parent does a 8 * WAITPID. 9 * 10 * The entry points into this file are: 11 * do_fork: perform the FORK system call 12 * do_srv_fork: special FORK, used by RS to create sys services 13 * do_exit: perform the EXIT system call (by calling exit_proc()) 14 * exit_proc: actually do the exiting, and tell VFS about it 15 * exit_restart: continue exiting a process after VFS has replied 16 * do_waitpid: perform the WAITPID system call 17 * wait_test: check whether a parent is waiting for a child 18 */ 19 20 #include "pm.h" 21 #include <sys/wait.h> 22 #include <assert.h> 23 #include <minix/callnr.h> 24 #include <minix/com.h> 25 #include <minix/sched.h> 26 #include <minix/vm.h> 27 #include <sys/ptrace.h> 28 #include <sys/resource.h> 29 #include <signal.h> 30 #include "mproc.h" 31 32 #define LAST_FEW 2 /* last few slots reserved for superuser */ 33 34 static void zombify(struct mproc *rmp); 35 static void check_parent(struct mproc *child, int try_cleanup); 36 static void tell_parent(struct mproc *child); 37 static void tell_tracer(struct mproc *child); 38 static void tracer_died(struct mproc *child); 39 static void cleanup(register struct mproc *rmp); 40 41 /*===========================================================================* 42 * do_fork * 43 *===========================================================================*/ 44 int do_fork() 45 { 46 /* The process pointed to by 'mp' has forked. Create a child process. */ 47 register struct mproc *rmp; /* pointer to parent */ 48 register struct mproc *rmc; /* pointer to child */ 49 pid_t new_pid; 50 static unsigned int next_child = 0; 51 int i, n = 0, s; 52 endpoint_t child_ep; 53 message m; 54 55 /* If tables might fill up during FORK, don't even start since recovery half 56 * way through is such a nuisance. 57 */ 58 rmp = mp; 59 if ((procs_in_use == NR_PROCS) || 60 (procs_in_use >= NR_PROCS-LAST_FEW && rmp->mp_effuid != 0)) 61 { 62 printf("PM: warning, process table is full!\n"); 63 return(EAGAIN); 64 } 65 66 /* Find a slot in 'mproc' for the child process. A slot must exist. */ 67 do { 68 next_child = (next_child+1) % NR_PROCS; 69 n++; 70 } while((mproc[next_child].mp_flags & IN_USE) && n <= NR_PROCS); 71 if(n > NR_PROCS) 72 panic("do_fork can't find child slot"); 73 if(next_child >= NR_PROCS || (mproc[next_child].mp_flags & IN_USE)) 74 panic("do_fork finds wrong child slot: %d", next_child); 75 76 /* Memory part of the forking. */ 77 if((s=vm_fork(rmp->mp_endpoint, next_child, &child_ep)) != OK) { 78 return s; 79 } 80 81 /* PM may not fail fork after call to vm_fork(), as VM calls sys_fork(). */ 82 83 rmc = &mproc[next_child]; 84 /* Set up the child and its memory map; copy its 'mproc' slot from parent. */ 85 procs_in_use++; 86 *rmc = *rmp; /* copy parent's process slot to child's */ 87 rmc->mp_parent = who_p; /* record child's parent */ 88 if (!(rmc->mp_trace_flags & TO_TRACEFORK)) { 89 rmc->mp_tracer = NO_TRACER; /* no tracer attached */ 90 rmc->mp_trace_flags = 0; 91 (void) sigemptyset(&rmc->mp_sigtrace); 92 } 93 94 /* Some system servers like to call regular fork, such as RS spawning 95 * recovery scripts; in this case PM will take care of their scheduling 96 * because RS cannot do so for non-system processes */ 97 if (rmc->mp_flags & PRIV_PROC) { 98 assert(rmc->mp_scheduler == NONE); 99 rmc->mp_scheduler = SCHED_PROC_NR; 100 } 101 102 /* Inherit only these flags. In normal fork(), PRIV_PROC is not inherited. */ 103 rmc->mp_flags &= (IN_USE|DELAY_CALL|TAINTED); 104 rmc->mp_child_utime = 0; /* reset administration */ 105 rmc->mp_child_stime = 0; /* reset administration */ 106 rmc->mp_exitstatus = 0; 107 rmc->mp_sigstatus = 0; 108 rmc->mp_endpoint = child_ep; /* passed back by VM */ 109 for (i = 0; i < NR_ITIMERS; i++) 110 rmc->mp_interval[i] = 0; /* reset timer intervals */ 111 112 /* Find a free pid for the child and put it in the table. */ 113 new_pid = get_free_pid(); 114 rmc->mp_pid = new_pid; /* assign pid to child */ 115 116 memset(&m, 0, sizeof(m)); 117 m.m_type = VFS_PM_FORK; 118 m.VFS_PM_ENDPT = rmc->mp_endpoint; 119 m.VFS_PM_PENDPT = rmp->mp_endpoint; 120 m.VFS_PM_CPID = rmc->mp_pid; 121 m.VFS_PM_REUID = -1; /* Not used by VFS_PM_FORK */ 122 m.VFS_PM_REGID = -1; /* Not used by VFS_PM_FORK */ 123 124 tell_vfs(rmc, &m); 125 126 /* Tell the tracer, if any, about the new child */ 127 if (rmc->mp_tracer != NO_TRACER) 128 sig_proc(rmc, SIGSTOP, TRUE /*trace*/, FALSE /* ksig */); 129 130 /* Do not reply until VFS is ready to process the fork 131 * request 132 */ 133 return SUSPEND; 134 } 135 136 /*===========================================================================* 137 * do_srv_fork * 138 *===========================================================================*/ 139 int do_srv_fork() 140 { 141 /* The process pointed to by 'mp' has forked. Create a child process. */ 142 register struct mproc *rmp; /* pointer to parent */ 143 register struct mproc *rmc; /* pointer to child */ 144 int s; 145 pid_t new_pid; 146 static unsigned int next_child = 0; 147 int i, n = 0; 148 endpoint_t child_ep; 149 message m; 150 151 /* Only RS is allowed to use srv_fork. */ 152 if (mp->mp_endpoint != RS_PROC_NR) 153 return EPERM; 154 155 /* If tables might fill up during FORK, don't even start since recovery half 156 * way through is such a nuisance. 157 */ 158 rmp = mp; 159 if ((procs_in_use == NR_PROCS) || 160 (procs_in_use >= NR_PROCS-LAST_FEW && rmp->mp_effuid != 0)) 161 { 162 printf("PM: warning, process table is full!\n"); 163 return(EAGAIN); 164 } 165 166 /* Find a slot in 'mproc' for the child process. A slot must exist. */ 167 do { 168 next_child = (next_child+1) % NR_PROCS; 169 n++; 170 } while((mproc[next_child].mp_flags & IN_USE) && n <= NR_PROCS); 171 if(n > NR_PROCS) 172 panic("do_fork can't find child slot"); 173 if(next_child >= NR_PROCS || (mproc[next_child].mp_flags & IN_USE)) 174 panic("do_fork finds wrong child slot: %d", next_child); 175 176 if((s=vm_fork(rmp->mp_endpoint, next_child, &child_ep)) != OK) { 177 return s; 178 } 179 180 rmc = &mproc[next_child]; 181 /* Set up the child and its memory map; copy its 'mproc' slot from parent. */ 182 procs_in_use++; 183 *rmc = *rmp; /* copy parent's process slot to child's */ 184 rmc->mp_parent = who_p; /* record child's parent */ 185 if (!(rmc->mp_trace_flags & TO_TRACEFORK)) { 186 rmc->mp_tracer = NO_TRACER; /* no tracer attached */ 187 rmc->mp_trace_flags = 0; 188 (void) sigemptyset(&rmc->mp_sigtrace); 189 } 190 /* inherit only these flags */ 191 rmc->mp_flags &= (IN_USE|PRIV_PROC|DELAY_CALL); 192 rmc->mp_child_utime = 0; /* reset administration */ 193 rmc->mp_child_stime = 0; /* reset administration */ 194 rmc->mp_exitstatus = 0; 195 rmc->mp_sigstatus = 0; 196 rmc->mp_endpoint = child_ep; /* passed back by VM */ 197 rmc->mp_realuid = m_in.m_lsys_pm_srv_fork.uid; 198 rmc->mp_effuid = m_in.m_lsys_pm_srv_fork.uid; 199 rmc->mp_realgid = m_in.m_lsys_pm_srv_fork.gid; 200 rmc->mp_effgid = m_in.m_lsys_pm_srv_fork.gid; 201 for (i = 0; i < NR_ITIMERS; i++) 202 rmc->mp_interval[i] = 0; /* reset timer intervals */ 203 204 /* Find a free pid for the child and put it in the table. */ 205 new_pid = get_free_pid(); 206 rmc->mp_pid = new_pid; /* assign pid to child */ 207 208 memset(&m, 0, sizeof(m)); 209 m.m_type = VFS_PM_SRV_FORK; 210 m.VFS_PM_ENDPT = rmc->mp_endpoint; 211 m.VFS_PM_PENDPT = rmp->mp_endpoint; 212 m.VFS_PM_CPID = rmc->mp_pid; 213 m.VFS_PM_REUID = m_in.m_lsys_pm_srv_fork.uid; 214 m.VFS_PM_REGID = m_in.m_lsys_pm_srv_fork.gid; 215 216 tell_vfs(rmc, &m); 217 218 /* Tell the tracer, if any, about the new child */ 219 if (rmc->mp_tracer != NO_TRACER) 220 sig_proc(rmc, SIGSTOP, TRUE /*trace*/, FALSE /* ksig */); 221 222 /* Wakeup the newly created process */ 223 reply(rmc-mproc, OK); 224 225 return rmc->mp_pid; 226 } 227 228 /*===========================================================================* 229 * do_exit * 230 *===========================================================================*/ 231 int do_exit() 232 { 233 /* Perform the exit(status) system call. The real work is done by exit_proc(), 234 * which is also called when a process is killed by a signal. System processes 235 * do not use PM's exit() to terminate. If they try to, we warn the user 236 * and send a SIGKILL signal to the system process. 237 */ 238 if(mp->mp_flags & PRIV_PROC) { 239 printf("PM: system process %d (%s) tries to exit(), sending SIGKILL\n", 240 mp->mp_endpoint, mp->mp_name); 241 sys_kill(mp->mp_endpoint, SIGKILL); 242 } 243 else { 244 exit_proc(mp, m_in.m_lc_pm_exit.status, FALSE /*dump_core*/); 245 } 246 return(SUSPEND); /* can't communicate from beyond the grave */ 247 } 248 249 /*===========================================================================* 250 * exit_proc * 251 *===========================================================================*/ 252 void exit_proc(rmp, exit_status, dump_core) 253 register struct mproc *rmp; /* pointer to the process to be terminated */ 254 int exit_status; /* the process' exit status (for parent) */ 255 int dump_core; /* flag indicating whether to dump core */ 256 { 257 /* A process is done. Release most of the process' possessions. If its 258 * parent is waiting, release the rest, else keep the process slot and 259 * become a zombie. 260 */ 261 register int proc_nr, proc_nr_e; 262 int r; 263 pid_t procgrp; 264 struct mproc *p_mp; 265 clock_t user_time, sys_time; 266 message m; 267 268 /* Do not create core files for set uid execution */ 269 if (dump_core && rmp->mp_realuid != rmp->mp_effuid) 270 dump_core = FALSE; 271 272 /* System processes are destroyed before informing VFS, meaning that VFS can 273 * not get their CPU state, so we can't generate a coredump for them either. 274 */ 275 if (dump_core && (rmp->mp_flags & PRIV_PROC)) 276 dump_core = FALSE; 277 278 proc_nr = (int) (rmp - mproc); /* get process slot number */ 279 proc_nr_e = rmp->mp_endpoint; 280 281 /* Remember a session leader's process group. */ 282 procgrp = (rmp->mp_pid == mp->mp_procgrp) ? mp->mp_procgrp : 0; 283 284 /* If the exited process has a timer pending, kill it. */ 285 if (rmp->mp_flags & ALARM_ON) set_alarm(rmp, (clock_t) 0); 286 287 /* Do accounting: fetch usage times and accumulate at parent. */ 288 if((r=sys_times(proc_nr_e, &user_time, &sys_time, NULL, NULL)) != OK) 289 panic("exit_proc: sys_times failed: %d", r); 290 291 p_mp = &mproc[rmp->mp_parent]; /* process' parent */ 292 p_mp->mp_child_utime += user_time + rmp->mp_child_utime; /* add user time */ 293 p_mp->mp_child_stime += sys_time + rmp->mp_child_stime; /* add system time */ 294 295 /* Tell the kernel the process is no longer runnable to prevent it from 296 * being scheduled in between the following steps. Then tell VFS that it 297 * the process has exited and finally, clean up the process at the kernel. 298 * This order is important so that VFS can tell drivers to cancel requests 299 * such as copying to/ from the exiting process, before it is gone. 300 */ 301 /* If the process is not yet stopped, we force a stop here. This means that 302 * the process may still have a delay call pending. For this reason, the main 303 * message loop discards requests from exiting processes. 304 */ 305 if (!(rmp->mp_flags & PROC_STOPPED)) { 306 if ((r = sys_stop(proc_nr_e)) != OK) /* stop the process */ 307 panic("sys_stop failed: %d", r); 308 rmp->mp_flags |= PROC_STOPPED; 309 } 310 311 if((r=vm_willexit(proc_nr_e)) != OK) { 312 panic("exit_proc: vm_willexit failed: %d", r); 313 } 314 vm_notify_sig_wrapper(rmp->mp_endpoint); 315 if (proc_nr_e == INIT_PROC_NR) 316 { 317 printf("PM: INIT died\n"); 318 return; 319 } 320 if (proc_nr_e == VFS_PROC_NR) 321 { 322 panic("exit_proc: VFS died: %d", r); 323 } 324 325 /* Tell VFS about the exiting process. */ 326 memset(&m, 0, sizeof(m)); 327 m.m_type = dump_core ? VFS_PM_DUMPCORE : VFS_PM_EXIT; 328 m.VFS_PM_ENDPT = rmp->mp_endpoint; 329 330 if (dump_core) { 331 m.VFS_PM_TERM_SIG = rmp->mp_sigstatus; 332 m.VFS_PM_PATH = rmp->mp_name; 333 } 334 335 tell_vfs(rmp, &m); 336 337 if (rmp->mp_flags & PRIV_PROC) 338 { 339 /* Destroy system processes without waiting for VFS. This is 340 * needed because the system process might be a block device 341 * driver that VFS is blocked waiting on. 342 */ 343 if((r= sys_clear(rmp->mp_endpoint)) != OK) 344 panic("exit_proc: sys_clear failed: %d", r); 345 } 346 347 /* Clean up most of the flags describing the process's state before the exit, 348 * and mark it as exiting. 349 */ 350 rmp->mp_flags &= (IN_USE|VFS_CALL|PRIV_PROC|TRACE_EXIT|PROC_STOPPED); 351 rmp->mp_flags |= EXITING; 352 353 /* Keep the process around until VFS is finished with it. */ 354 355 rmp->mp_exitstatus = (char) exit_status; 356 357 /* For normal exits, try to notify the parent as soon as possible. 358 * For core dumps, notify the parent only once the core dump has been made. 359 */ 360 if (!dump_core) 361 zombify(rmp); 362 363 /* If the process has children, disinherit them. INIT is the new parent. */ 364 for (rmp = &mproc[0]; rmp < &mproc[NR_PROCS]; rmp++) { 365 if (!(rmp->mp_flags & IN_USE)) continue; 366 if (rmp->mp_tracer == proc_nr) { 367 /* This child's tracer died. Do something sensible. */ 368 tracer_died(rmp); 369 } 370 if (rmp->mp_parent == proc_nr) { 371 /* 'rmp' now points to a child to be disinherited. */ 372 rmp->mp_parent = INIT_PROC_NR; 373 374 /* If the process is making a VFS call, remember that we set 375 * a new parent. This prevents FORK from replying to the wrong 376 * parent upon completion. 377 */ 378 if (rmp->mp_flags & VFS_CALL) 379 rmp->mp_flags |= NEW_PARENT; 380 381 /* Notify new parent. */ 382 if (rmp->mp_flags & ZOMBIE) 383 check_parent(rmp, TRUE /*try_cleanup*/); 384 } 385 } 386 387 /* Send a hangup to the process' process group if it was a session leader. */ 388 if (procgrp != 0) check_sig(-procgrp, SIGHUP, FALSE /* ksig */); 389 } 390 391 /*===========================================================================* 392 * exit_restart * 393 *===========================================================================*/ 394 void exit_restart(rmp, dump_core) 395 struct mproc *rmp; /* pointer to the process being terminated */ 396 int dump_core; /* flag indicating whether to dump core */ 397 { 398 /* VFS replied to our exit or coredump request. Perform the second half of the 399 * exit code. 400 */ 401 int r; 402 403 if((r = sched_stop(rmp->mp_scheduler, rmp->mp_endpoint)) != OK) { 404 /* If the scheduler refuses to give up scheduling, there is 405 * little we can do, except report it. This may cause problems 406 * later on, if this scheduler is asked to schedule another proc 407 * that has an endpoint->schedproc mapping identical to the proc 408 * we just tried to stop scheduling. 409 */ 410 printf("PM: The scheduler did not want to give up " 411 "scheduling %s, ret=%d.\n", rmp->mp_name, r); 412 } 413 414 /* sched_stop is either called when the process is exiting or it is 415 * being moved between schedulers. If it is being moved between 416 * schedulers, we need to set the mp_scheduler to NONE so that PM 417 * doesn't forward messages to the process' scheduler while being moved 418 * (such as sched_nice). */ 419 rmp->mp_scheduler = NONE; 420 421 /* For core dumps, now is the right time to try to contact the parent. */ 422 if (dump_core) 423 zombify(rmp); 424 425 if (!(rmp->mp_flags & PRIV_PROC)) 426 { 427 /* destroy the (user) process */ 428 if((r=sys_clear(rmp->mp_endpoint)) != OK) 429 panic("exit_restart: sys_clear failed: %d", r); 430 } 431 432 /* Release the memory occupied by the child. */ 433 if((r=vm_exit(rmp->mp_endpoint)) != OK) { 434 panic("exit_restart: vm_exit failed: %d", r); 435 } 436 437 if (rmp->mp_flags & TRACE_EXIT) 438 { 439 /* Wake up the tracer, completing the ptrace(T_EXIT) call */ 440 mproc[rmp->mp_tracer].mp_reply.m_pm_lc_ptrace.data = 0; 441 reply(rmp->mp_tracer, OK); 442 } 443 444 /* Clean up if the parent has collected the exit status */ 445 if (rmp->mp_flags & TOLD_PARENT) 446 cleanup(rmp); 447 } 448 449 /*===========================================================================* 450 * do_waitpid * 451 *===========================================================================*/ 452 int do_waitpid() 453 { 454 /* A process wants to wait for a child to terminate. If a child is already 455 * waiting, go clean it up and let this WAITPID call terminate. Otherwise, 456 * really wait. 457 * A process calling WAITPID never gets a reply in the usual way at the end 458 * of the main loop (unless WNOHANG is set or no qualifying child exists). 459 * If a child has already exited, the routine tell_parent() sends the reply 460 * to awaken the caller. 461 */ 462 register struct mproc *rp; 463 int i, pidarg, options, children; 464 465 /* Set internal variables. */ 466 pidarg = m_in.m_lc_pm_waitpid.pid; /* 1st param */ 467 options = m_in.m_lc_pm_waitpid.options; /* 3rd param */ 468 if (pidarg == 0) pidarg = -mp->mp_procgrp; /* pidarg < 0 ==> proc grp */ 469 470 /* Is there a child waiting to be collected? At this point, pidarg != 0: 471 * pidarg > 0 means pidarg is pid of a specific process to wait for 472 * pidarg == -1 means wait for any child 473 * pidarg < -1 means wait for any child whose process group = -pidarg 474 */ 475 children = 0; 476 for (rp = &mproc[0]; rp < &mproc[NR_PROCS]; rp++) { 477 if ((rp->mp_flags & (IN_USE | TOLD_PARENT)) != IN_USE) continue; 478 if (rp->mp_parent != who_p && rp->mp_tracer != who_p) continue; 479 if (rp->mp_parent != who_p && (rp->mp_flags & ZOMBIE)) continue; 480 481 /* The value of pidarg determines which children qualify. */ 482 if (pidarg > 0 && pidarg != rp->mp_pid) continue; 483 if (pidarg < -1 && -pidarg != rp->mp_procgrp) continue; 484 485 children++; /* this child is acceptable */ 486 487 if (rp->mp_tracer == who_p) { 488 if (rp->mp_flags & TRACE_ZOMBIE) { 489 /* Traced child meets the pid test and has exited. */ 490 tell_tracer(rp); 491 check_parent(rp, TRUE /*try_cleanup*/); 492 return(SUSPEND); 493 } 494 if (rp->mp_flags & TRACE_STOPPED) { 495 /* This child meets the pid test and is being traced. 496 * Deliver a signal to the tracer, if any. 497 */ 498 for (i = 1; i < _NSIG; i++) { 499 if (sigismember(&rp->mp_sigtrace, i)) { 500 sigdelset(&rp->mp_sigtrace, i); 501 502 mp->mp_reply.m_pm_lc_waitpid.status = W_STOPCODE(i); 503 return(rp->mp_pid); 504 } 505 } 506 } 507 } 508 509 if (rp->mp_parent == who_p) { 510 if (rp->mp_flags & ZOMBIE) { 511 /* This child meets the pid test and has exited. */ 512 tell_parent(rp); /* this child has already exited */ 513 if (!(rp->mp_flags & VFS_CALL)) 514 cleanup(rp); 515 return(SUSPEND); 516 } 517 } 518 } 519 520 /* No qualifying child has exited. Wait for one, unless none exists. */ 521 if (children > 0) { 522 /* At least 1 child meets the pid test exists, but has not exited. */ 523 if (options & WNOHANG) { 524 return(0); /* parent does not want to wait */ 525 } 526 mp->mp_flags |= WAITING; /* parent wants to wait */ 527 mp->mp_wpid = (pid_t) pidarg; /* save pid for later */ 528 return(SUSPEND); /* do not reply, let it wait */ 529 } else { 530 /* No child even meets the pid test. Return error immediately. */ 531 return(ECHILD); /* no - parent has no children */ 532 } 533 } 534 535 /*===========================================================================* 536 * wait_test * 537 *===========================================================================*/ 538 int wait_test(rmp, child) 539 struct mproc *rmp; /* process that may be waiting */ 540 struct mproc *child; /* process that may be waited for */ 541 { 542 /* See if a parent or tracer process is waiting for a child process. 543 * A tracer is considered to be a pseudo-parent. 544 */ 545 int parent_waiting, right_child; 546 pid_t pidarg; 547 548 pidarg = rmp->mp_wpid; /* who's being waited for? */ 549 parent_waiting = rmp->mp_flags & WAITING; 550 right_child = /* child meets one of the 3 tests? */ 551 (pidarg == -1 || pidarg == child->mp_pid || 552 -pidarg == child->mp_procgrp); 553 554 return (parent_waiting && right_child); 555 } 556 557 /*===========================================================================* 558 * zombify * 559 *===========================================================================*/ 560 static void zombify(rmp) 561 struct mproc *rmp; 562 { 563 /* Zombify a process. First check if the exiting process is traced by a process 564 * other than its parent; if so, the tracer must be notified about the exit 565 * first. Once that is done, the real parent may be notified about the exit of 566 * its child. 567 */ 568 struct mproc *t_mp; 569 570 if (rmp->mp_flags & (TRACE_ZOMBIE | ZOMBIE)) 571 panic("zombify: process was already a zombie"); 572 573 /* See if we have to notify a tracer process first. */ 574 if (rmp->mp_tracer != NO_TRACER && rmp->mp_tracer != rmp->mp_parent) { 575 rmp->mp_flags |= TRACE_ZOMBIE; 576 577 t_mp = &mproc[rmp->mp_tracer]; 578 579 /* Do not bother sending SIGCHLD signals to tracers. */ 580 if (!wait_test(t_mp, rmp)) 581 return; 582 583 tell_tracer(rmp); 584 } 585 else { 586 rmp->mp_flags |= ZOMBIE; 587 } 588 589 /* No tracer, or tracer is parent, or tracer has now been notified. */ 590 check_parent(rmp, FALSE /*try_cleanup*/); 591 } 592 593 /*===========================================================================* 594 * check_parent * 595 *===========================================================================*/ 596 static void check_parent(child, try_cleanup) 597 struct mproc *child; /* tells which process is exiting */ 598 int try_cleanup; /* clean up the child when done? */ 599 { 600 /* We would like to inform the parent of an exiting child about the child's 601 * death. If the parent is waiting for the child, tell it immediately; 602 * otherwise, send it a SIGCHLD signal. 603 * 604 * Note that we may call this function twice on a single child; first with 605 * its original parent, later (if the parent died) with INIT as its parent. 606 */ 607 struct mproc *p_mp; 608 609 p_mp = &mproc[child->mp_parent]; 610 611 if (p_mp->mp_flags & EXITING) { 612 /* This may trigger if the child of a dead parent dies. The child will 613 * be assigned to INIT and rechecked shortly after. Do nothing. 614 */ 615 } 616 else if (wait_test(p_mp, child)) { 617 tell_parent(child); 618 619 /* The 'try_cleanup' flag merely saves us from having to be really 620 * careful with statement ordering in exit_proc() and exit_restart(). 621 */ 622 if (try_cleanup && !(child->mp_flags & VFS_CALL)) 623 cleanup(child); 624 } 625 else { 626 /* Parent is not waiting. */ 627 sig_proc(p_mp, SIGCHLD, TRUE /*trace*/, FALSE /* ksig */); 628 } 629 } 630 631 /*===========================================================================* 632 * tell_parent * 633 *===========================================================================*/ 634 static void tell_parent(child) 635 register struct mproc *child; /* tells which process is exiting */ 636 { 637 int mp_parent; 638 struct mproc *parent; 639 640 mp_parent= child->mp_parent; 641 if (mp_parent <= 0) 642 panic("tell_parent: bad value in mp_parent: %d", mp_parent); 643 if(!(child->mp_flags & ZOMBIE)) 644 panic("tell_parent: child not a zombie"); 645 if(child->mp_flags & TOLD_PARENT) 646 panic("tell_parent: telling parent again"); 647 parent = &mproc[mp_parent]; 648 649 /* Wake up the parent by sending the reply message. */ 650 parent->mp_reply.m_pm_lc_waitpid.status = 651 W_EXITCODE(child->mp_exitstatus, child->mp_sigstatus); 652 reply(child->mp_parent, child->mp_pid); 653 parent->mp_flags &= ~WAITING; /* parent no longer waiting */ 654 child->mp_flags &= ~ZOMBIE; /* child no longer a zombie */ 655 child->mp_flags |= TOLD_PARENT; /* avoid informing parent twice */ 656 } 657 658 /*===========================================================================* 659 * tell_tracer * 660 *===========================================================================*/ 661 static void tell_tracer(child) 662 struct mproc *child; /* tells which process is exiting */ 663 { 664 int mp_tracer; 665 struct mproc *tracer; 666 667 mp_tracer = child->mp_tracer; 668 if (mp_tracer <= 0) 669 panic("tell_tracer: bad value in mp_tracer: %d", mp_tracer); 670 if(!(child->mp_flags & TRACE_ZOMBIE)) 671 panic("tell_tracer: child not a zombie"); 672 tracer = &mproc[mp_tracer]; 673 674 tracer->mp_reply.m_pm_lc_waitpid.status = 675 W_EXITCODE(child->mp_exitstatus, (child->mp_sigstatus & 0377)); 676 reply(child->mp_tracer, child->mp_pid); 677 tracer->mp_flags &= ~WAITING; /* tracer no longer waiting */ 678 child->mp_flags &= ~TRACE_ZOMBIE; /* child no longer zombie to tracer */ 679 child->mp_flags |= ZOMBIE; /* child is now zombie to parent */ 680 } 681 682 /*===========================================================================* 683 * tracer_died * 684 *===========================================================================*/ 685 static void tracer_died(child) 686 struct mproc *child; /* process being traced */ 687 { 688 /* The process that was tracing the given child, has died for some reason. 689 * This is really the tracer's fault, but we can't let INIT deal with this. 690 */ 691 692 child->mp_tracer = NO_TRACER; 693 child->mp_flags &= ~TRACE_EXIT; 694 695 /* If the tracer died while the child was running or stopped, we have no 696 * idea what state the child is in. Avoid a trainwreck, by killing the child. 697 * Note that this may cause cascading exits. 698 */ 699 if (!(child->mp_flags & EXITING)) { 700 sig_proc(child, SIGKILL, TRUE /*trace*/, FALSE /* ksig */); 701 702 return; 703 } 704 705 /* If the tracer died while the child was telling it about its own death, 706 * forget about the tracer and notify the real parent instead. 707 */ 708 if (child->mp_flags & TRACE_ZOMBIE) { 709 child->mp_flags &= ~TRACE_ZOMBIE; 710 child->mp_flags |= ZOMBIE; 711 712 check_parent(child, TRUE /*try_cleanup*/); 713 } 714 } 715 716 /*===========================================================================* 717 * cleanup * 718 *===========================================================================*/ 719 static void cleanup(rmp) 720 register struct mproc *rmp; /* tells which process is exiting */ 721 { 722 /* Release the process table entry and reinitialize some field. */ 723 rmp->mp_pid = 0; 724 rmp->mp_flags = 0; 725 rmp->mp_child_utime = 0; 726 rmp->mp_child_stime = 0; 727 procs_in_use--; 728 } 729 730