kernel/exit.c

/* */
This source file includes following definitions.
generate
send_sig
notify_parent
release
bad_task_ptr
audit_ptree
session_of_pgrp
kill_pg
kill_sl
kill_proc
sys_kill
is_orphaned_pgrp
has_stopped_jobs
forget_original_parent
exit_files
exit_fs
exit_sighand
exit_mm
exit_notify
do_exit
sys_exit
sys_wait4
sys_waitpid
   1 /*
   2  *  linux/kernel/exit.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6 
   7 #undef DEBUG_PROC_TREE
   8 
   9 #include <linux/wait.h>
  10 #include <linux/errno.h>
  11 #include <linux/signal.h>
  12 #include <linux/sched.h>
  13 #include <linux/kernel.h>
  14 #include <linux/resource.h>
  15 #include <linux/mm.h>
  16 #include <linux/tty.h>
  17 #include <linux/malloc.h>
  18 
  19 #include <asm/segment.h>
  20 extern void sem_exit (void);
  21 
  22 int getrusage(struct task_struct *, int, struct rusage *);
  23 
  24 static int generate(unsigned long sig, struct task_struct * p)
     /*  */
  25 {
  26         unsigned long mask = 1 << (sig-1);
  27         struct sigaction * sa = sig + p->sig->action - 1;
  28 
  29         /* always generate signals for traced processes ??? */
  30         if (!(p->flags & PF_PTRACED)) {
  31                 /* don't bother with ignored signals (but SIGCHLD is special) */
  32                 if (sa->sa_handler == SIG_IGN && sig != SIGCHLD)
  33                         return 0;
  34                 /* some signals are ignored by default.. (but SIGCONT already did its deed) */
  35                 if ((sa->sa_handler == SIG_DFL) &&
  36                     (sig == SIGCONT || sig == SIGCHLD || sig == SIGWINCH))
  37                         return 0;
  38         }
  39         p->signal |= mask;
  40         if (p->state == TASK_INTERRUPTIBLE && (p->signal & ~p->blocked))
  41                 wake_up_process(p);
  42         return 1;
  43 }
  44 
  45 int send_sig(unsigned long sig,struct task_struct * p,int priv)
     /*  */
  46 {
  47         if (!p || sig > 32)
  48                 return -EINVAL;
  49         if (!priv && ((sig != SIGCONT) || (current->session != p->session)) &&
  50             (current->euid != p->euid) && (current->euid != p->uid) && !suser())
  51                 return -EPERM;
  52         if (!sig)
  53                 return 0;
  54         /*
  55          * Forget it if the process is already zombie'd.
  56          */
  57         if (!p->sig)
  58                 return 0;
  59         if ((sig == SIGKILL) || (sig == SIGCONT)) {
  60                 if (p->state == TASK_STOPPED)
  61                         wake_up_process(p);
  62                 p->exit_code = 0;
  63                 p->signal &= ~( (1<<(SIGSTOP-1)) | (1<<(SIGTSTP-1)) |
  64                                 (1<<(SIGTTIN-1)) | (1<<(SIGTTOU-1)) );
  65         }
  66         if (sig == SIGSTOP || sig == SIGTSTP || sig == SIGTTIN || sig == SIGTTOU)
  67                 p->signal &= ~(1<<(SIGCONT-1));
  68         /* Actually generate the signal */
  69         generate(sig,p);
  70         return 0;
  71 }
  72 
  73 void notify_parent(struct task_struct * tsk)
     /*  */
  74 {
  75         if (tsk->p_pptr == task[1])
  76                 tsk->exit_signal = SIGCHLD;
  77         send_sig(tsk->exit_signal, tsk->p_pptr, 1);
  78         wake_up_interruptible(&tsk->p_pptr->wait_chldexit);
  79 }
  80 
  81 void release(struct task_struct * p)
     /*  */
  82 {
  83         int i;
  84 
  85         if (!p)
  86                 return;
  87         if (p == current) {
  88                 printk("task releasing itself\n");
  89                 return;
  90         }
  91         for (i=1 ; i<NR_TASKS ; i++)
  92                 if (task[i] == p) {
  93                         nr_tasks--;
  94                         task[i] = NULL;
  95                         REMOVE_LINKS(p);
  96                         if (STACK_MAGIC != *(unsigned long *)p->kernel_stack_page)
  97                                 printk(KERN_ALERT "release: %s kernel stack corruption. Aiee\n", p->comm);
  98                         free_page(p->kernel_stack_page);
  99                         current->cmin_flt += p->min_flt + p->cmin_flt;
 100                         current->cmaj_flt += p->maj_flt + p->cmaj_flt;
 101                         kfree(p);
 102                         return;
 103                 }
 104         panic("trying to release non-existent task");
 105 }
 106 
 107 #ifdef DEBUG_PROC_TREE
 108 /*
 109  * Check to see if a task_struct pointer is present in the task[] array
 110  * Return 0 if found, and 1 if not found.
 111  */
 112 int bad_task_ptr(struct task_struct *p)
     /*  */
 113 {
 114         int     i;
 115 
 116         if (!p)
 117                 return 0;
 118         for (i=0 ; i<NR_TASKS ; i++)
 119                 if (task[i] == p)
 120                         return 0;
 121         return 1;
 122 }
 123         
 124 /*
 125  * This routine scans the pid tree and makes sure the rep invariant still
 126  * holds.  Used for debugging only, since it's very slow....
 127  *
 128  * It looks a lot scarier than it really is.... we're doing nothing more
 129  * than verifying the doubly-linked list found in p_ysptr and p_osptr, 
 130  * and checking it corresponds with the process tree defined by p_cptr and 
 131  * p_pptr;
 132  */
 133 void audit_ptree(void)
     /*  */
 134 {
 135         int     i;
 136 
 137         for (i=1 ; i<NR_TASKS ; i++) {
 138                 if (!task[i])
 139                         continue;
 140                 if (bad_task_ptr(task[i]->p_pptr))
 141                         printk("Warning, pid %d's parent link is bad\n",
 142                                 task[i]->pid);
 143                 if (bad_task_ptr(task[i]->p_cptr))
 144                         printk("Warning, pid %d's child link is bad\n",
 145                                 task[i]->pid);
 146                 if (bad_task_ptr(task[i]->p_ysptr))
 147                         printk("Warning, pid %d's ys link is bad\n",
 148                                 task[i]->pid);
 149                 if (bad_task_ptr(task[i]->p_osptr))
 150                         printk("Warning, pid %d's os link is bad\n",
 151                                 task[i]->pid);
 152                 if (task[i]->p_pptr == task[i])
 153                         printk("Warning, pid %d parent link points to self\n",
 154                                 task[i]->pid);
 155                 if (task[i]->p_cptr == task[i])
 156                         printk("Warning, pid %d child link points to self\n",
 157                                 task[i]->pid);
 158                 if (task[i]->p_ysptr == task[i])
 159                         printk("Warning, pid %d ys link points to self\n",
 160                                 task[i]->pid);
 161                 if (task[i]->p_osptr == task[i])
 162                         printk("Warning, pid %d os link points to self\n",
 163                                 task[i]->pid);
 164                 if (task[i]->p_osptr) {
 165                         if (task[i]->p_pptr != task[i]->p_osptr->p_pptr)
 166                                 printk(
 167                         "Warning, pid %d older sibling %d parent is %d\n",
 168                                 task[i]->pid, task[i]->p_osptr->pid,
 169                                 task[i]->p_osptr->p_pptr->pid);
 170                         if (task[i]->p_osptr->p_ysptr != task[i])
 171                                 printk(
 172                 "Warning, pid %d older sibling %d has mismatched ys link\n",
 173                                 task[i]->pid, task[i]->p_osptr->pid);
 174                 }
 175                 if (task[i]->p_ysptr) {
 176                         if (task[i]->p_pptr != task[i]->p_ysptr->p_pptr)
 177                                 printk(
 178                         "Warning, pid %d younger sibling %d parent is %d\n",
 179                                 task[i]->pid, task[i]->p_osptr->pid,
 180                                 task[i]->p_osptr->p_pptr->pid);
 181                         if (task[i]->p_ysptr->p_osptr != task[i])
 182                                 printk(
 183                 "Warning, pid %d younger sibling %d has mismatched os link\n",
 184                                 task[i]->pid, task[i]->p_ysptr->pid);
 185                 }
 186                 if (task[i]->p_cptr) {
 187                         if (task[i]->p_cptr->p_pptr != task[i])
 188                                 printk(
 189                         "Warning, pid %d youngest child %d has mismatched parent link\n",
 190                                 task[i]->pid, task[i]->p_cptr->pid);
 191                         if (task[i]->p_cptr->p_ysptr)
 192                                 printk(
 193                         "Warning, pid %d youngest child %d has non-NULL ys link\n",
 194                                 task[i]->pid, task[i]->p_cptr->pid);
 195                 }
 196         }
 197 }
 198 #endif /* DEBUG_PROC_TREE */
 199 
 200 /*
 201  * This checks not only the pgrp, but falls back on the pid if no
 202  * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 203  * without this...
 204  */
 205 int session_of_pgrp(int pgrp)
     /*  */
 206 {
 207         struct task_struct *p;
 208         int fallback;
 209 
 210         fallback = -1;
 211         for_each_task(p) {
 212                 if (p->session <= 0)
 213                         continue;
 214                 if (p->pgrp == pgrp)
 215                         return p->session;
 216                 if (p->pid == pgrp)
 217                         fallback = p->session;
 218         }
 219         return fallback;
 220 }
 221 
 222 /*
 223  * kill_pg() sends a signal to a process group: this is what the tty
 224  * control characters do (^C, ^Z etc)
 225  */
 226 int kill_pg(int pgrp, int sig, int priv)
     /*  */
 227 {
 228         struct task_struct *p;
 229         int err,retval = -ESRCH;
 230         int found = 0;
 231 
 232         if (sig<0 || sig>32 || pgrp<=0)
 233                 return -EINVAL;
 234         for_each_task(p) {
 235                 if (p->pgrp == pgrp) {
 236                         if ((err = send_sig(sig,p,priv)) != 0)
 237                                 retval = err;
 238                         else
 239                                 found++;
 240                 }
 241         }
 242         return(found ? 0 : retval);
 243 }
 244 
 245 /*
 246  * kill_sl() sends a signal to the session leader: this is used
 247  * to send SIGHUP to the controlling process of a terminal when
 248  * the connection is lost.
 249  */
 250 int kill_sl(int sess, int sig, int priv)
     /*  */
 251 {
 252         struct task_struct *p;
 253         int err,retval = -ESRCH;
 254         int found = 0;
 255 
 256         if (sig<0 || sig>32 || sess<=0)
 257                 return -EINVAL;
 258         for_each_task(p) {
 259                 if (p->session == sess && p->leader) {
 260                         if ((err = send_sig(sig,p,priv)) != 0)
 261                                 retval = err;
 262                         else
 263                                 found++;
 264                 }
 265         }
 266         return(found ? 0 : retval);
 267 }
 268 
 269 int kill_proc(int pid, int sig, int priv)
     /*  */
 270 {
 271         struct task_struct *p;
 272 
 273         if (sig<0 || sig>32)
 274                 return -EINVAL;
 275         for_each_task(p) {
 276                 if (p && p->pid == pid)
 277                         return send_sig(sig,p,priv);
 278         }
 279         return(-ESRCH);
 280 }
 281 
 282 /*
 283  * POSIX specifies that kill(-1,sig) is unspecified, but what we have
 284  * is probably wrong.  Should make it like BSD or SYSV.
 285  */
 286 asmlinkage int sys_kill(int pid,int sig)
     /*  */
 287 {
 288         int err, retval = 0, count = 0;
 289 
 290         if (!pid)
 291                 return(kill_pg(current->pgrp,sig,0));
 292         if (pid == -1) {
 293                 struct task_struct * p;
 294                 for_each_task(p) {
 295                         if (p->pid > 1 && p != current) {
 296                                 ++count;
 297                                 if ((err = send_sig(sig,p,0)) != -EPERM)
 298                                         retval = err;
 299                         }
 300                 }
 301                 return(count ? retval : -ESRCH);
 302         }
 303         if (pid < 0) 
 304                 return(kill_pg(-pid,sig,0));
 305         /* Normal kill */
 306         return(kill_proc(pid,sig,0));
 307 }
 308 
 309 /*
 310  * Determine if a process group is "orphaned", according to the POSIX
 311  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 312  * by terminal-generated stop signals.  Newly orphaned process groups are 
 313  * to receive a SIGHUP and a SIGCONT.
 314  * 
 315  * "I ask you, have you ever known what it is to be an orphan?"
 316  */
 317 int is_orphaned_pgrp(int pgrp)
     /*  */
 318 {
 319         struct task_struct *p;
 320 
 321         for_each_task(p) {
 322                 if ((p->pgrp != pgrp) || 
 323                     (p->state == TASK_ZOMBIE) ||
 324                     (p->p_pptr->pid == 1))
 325                         continue;
 326                 if ((p->p_pptr->pgrp != pgrp) &&
 327                     (p->p_pptr->session == p->session))
 328                         return 0;
 329         }
 330         return(1);      /* (sighing) "Often!" */
 331 }
 332 
 333 static int has_stopped_jobs(int pgrp)
     /*  */
 334 {
 335         struct task_struct * p;
 336 
 337         for_each_task(p) {
 338                 if (p->pgrp != pgrp)
 339                         continue;
 340                 if (p->state == TASK_STOPPED)
 341                         return(1);
 342         }
 343         return(0);
 344 }
 345 
 346 static void forget_original_parent(struct task_struct * father)
     /*  */
 347 {
 348         struct task_struct * p;
 349 
 350         for_each_task(p) {
 351                 if (p->p_opptr == father)
 352                         if (task[1])
 353                                 p->p_opptr = task[1];
 354                         else
 355                                 p->p_opptr = task[0];
 356         }
 357 }
 358 
 359 void exit_files(struct task_struct *tsk)
     /*  */
 360 {
 361         struct files_struct * files = tsk->files;
 362 
 363         if (files) {
 364                 tsk->files = NULL;
 365                 if (!--files->count) {
 366                         int i;
 367                         for (i=0 ; i<NR_OPEN ; i++) {
 368                                 struct file * filp = files->fd[i];
 369                                 if (!filp)
 370                                         continue;
 371                                 files->fd[i] = NULL;
 372                                 close_fp(filp);
 373                         }
 374                         kfree(files);
 375                 }
 376         }
 377 }
 378 
 379 void exit_fs(struct task_struct *tsk)
     /*  */
 380 {
 381         struct fs_struct * fs = tsk->fs;
 382 
 383         if (fs) {
 384                 tsk->fs = NULL;
 385                 if (!--fs->count) {
 386                         iput(fs->root);
 387                         iput(fs->pwd);
 388                         kfree(fs);
 389                 }
 390         }
 391 }
 392 
 393 void exit_sighand(struct task_struct *tsk)
     /*  */
 394 {
 395         struct signal_struct * sig = tsk->sig;
 396 
 397         if (sig) {
 398                 tsk->sig = NULL;
 399                 if (!--sig->count) {
 400                         kfree(sig);
 401                 }
 402         }
 403 }
 404 
 405 static void exit_mm(void)
     /*  */
 406 {
 407         struct mm_struct * mm = current->mm;
 408 
 409         current->swappable = 0;
 410         if (mm) {
 411                 if (!--mm->count) {
 412                         exit_mmap(mm);
 413                         free_page_tables(current);
 414                         kfree(mm);
 415                 }
 416                 current->mm = NULL;
 417         }
 418 }
 419 
 420 /* 
 421  * Send signals to all our closest relatives so that they know
 422  * to properly mourn us..
 423  */
 424 static void exit_notify(void)
     /*  */
 425 {
 426         struct task_struct * p;
 427 
 428         forget_original_parent(current);
 429         /* 
 430          * Check to see if any process groups have become orphaned
 431          * as a result of our exiting, and if they have any stopped
 432          * jobs, send them a SIGUP and then a SIGCONT.  (POSIX 3.2.2.2)
 433          *
 434          * Case i: Our father is in a different pgrp than we are
 435          * and we were the only connection outside, so our pgrp
 436          * is about to become orphaned.
 437          */
 438         if ((current->p_pptr->pgrp != current->pgrp) &&
 439             (current->p_pptr->session == current->session) &&
 440             is_orphaned_pgrp(current->pgrp) &&
 441             has_stopped_jobs(current->pgrp)) {
 442                 kill_pg(current->pgrp,SIGHUP,1);
 443                 kill_pg(current->pgrp,SIGCONT,1);
 444         }
 445         /* Let father know we died */
 446         notify_parent(current);
 447         
 448         /*
 449          * This loop does two things:
 450          * 
 451          * A.  Make init inherit all the child processes
 452          * B.  Check to see if any process groups have become orphaned
 453          *      as a result of our exiting, and if they have any stopped
 454          *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 455          */
 456         while ((p = current->p_cptr) != NULL) {
 457                 current->p_cptr = p->p_osptr;
 458                 p->p_ysptr = NULL;
 459                 p->flags &= ~(PF_PTRACED|PF_TRACESYS);
 460                 if (task[1] && task[1] != current)
 461                         p->p_pptr = task[1];
 462                 else
 463                         p->p_pptr = task[0];
 464                 p->p_osptr = p->p_pptr->p_cptr;
 465                 p->p_osptr->p_ysptr = p;
 466                 p->p_pptr->p_cptr = p;
 467                 if (p->state == TASK_ZOMBIE)
 468                         notify_parent(p);
 469                 /*
 470                  * process group orphan check
 471                  * Case ii: Our child is in a different pgrp 
 472                  * than we are, and it was the only connection
 473                  * outside, so the child pgrp is now orphaned.
 474                  */
 475                 if ((p->pgrp != current->pgrp) &&
 476                     (p->session == current->session) &&
 477                     is_orphaned_pgrp(p->pgrp) &&
 478                     has_stopped_jobs(p->pgrp)) {
 479                         kill_pg(p->pgrp,SIGHUP,1);
 480                         kill_pg(p->pgrp,SIGCONT,1);
 481                 }
 482         }
 483         if (current->leader)
 484                 disassociate_ctty(1);
 485 }
 486 
 487 NORET_TYPE void do_exit(long code)
     /*  */
 488 {
 489         if (intr_count) {
 490                 printk("Aiee, killing interrupt handler\n");
 491                 intr_count = 0;
 492         }
 493 fake_volatile:
 494         current->flags |= PF_EXITING;
 495         del_timer(&current->real_timer);
 496         sem_exit();
 497         exit_mm();
 498         exit_files(current);
 499         exit_fs(current);
 500         exit_sighand(current);
 501         exit_thread();
 502         exit_notify();
 503         current->state = TASK_ZOMBIE;
 504         current->exit_code = code;
 505 #ifdef DEBUG_PROC_TREE
 506         audit_ptree();
 507 #endif
 508         if (current->exec_domain && current->exec_domain->use_count)
 509                 (*current->exec_domain->use_count)--;
 510         if (current->binfmt && current->binfmt->use_count)
 511                 (*current->binfmt->use_count)--;
 512         schedule();
 513 /*
 514  * In order to get rid of the "volatile function does return" message
 515  * I did this little loop that confuses gcc to think do_exit really
 516  * is volatile. In fact it's schedule() that is volatile in some
 517  * circumstances: when current->state = ZOMBIE, schedule() never
 518  * returns.
 519  *
 520  * In fact the natural way to do all this is to have the label and the
 521  * goto right after each other, but I put the fake_volatile label at
 522  * the start of the function just in case something /really/ bad
 523  * happens, and the schedule returns. This way we can try again. I'm
 524  * not paranoid: it's just that everybody is out to get me.
 525  */
 526         goto fake_volatile;
 527 }
 528 
 529 asmlinkage int sys_exit(int error_code)
     /*  */
 530 {
 531         do_exit((error_code&0xff)<<8);
 532 }
 533 
 534 asmlinkage int sys_wait4(pid_t pid,unsigned int * stat_addr, int options, struct rusage * ru)
     /*  */
 535 {
 536         int flag, retval;
 537         struct wait_queue wait = { current, NULL };
 538         struct task_struct *p;
 539 
 540         if (stat_addr) {
 541                 flag = verify_area(VERIFY_WRITE, stat_addr, sizeof(*stat_addr));
 542                 if (flag)
 543                         return flag;
 544         }
 545         add_wait_queue(&current->wait_chldexit,&wait);
 546 repeat:
 547         flag=0;
 548         for (p = current->p_cptr ; p ; p = p->p_osptr) {
 549                 if (pid>0) {
 550                         if (p->pid != pid)
 551                                 continue;
 552                 } else if (!pid) {
 553                         if (p->pgrp != current->pgrp)
 554                                 continue;
 555                 } else if (pid != -1) {
 556                         if (p->pgrp != -pid)
 557                                 continue;
 558                 }
 559                 /* wait for cloned processes iff the __WCLONE flag is set */
 560                 if ((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
 561                         continue;
 562                 flag = 1;
 563                 switch (p->state) {
 564                         case TASK_STOPPED:
 565                                 if (!p->exit_code)
 566                                         continue;
 567                                 if (!(options & WUNTRACED) && !(p->flags & PF_PTRACED))
 568                                         continue;
 569                                 if (stat_addr)
 570                                         put_user((p->exit_code << 8) | 0x7f,
 571                                                 stat_addr);
 572                                 p->exit_code = 0;
 573                                 if (ru != NULL)
 574                                         getrusage(p, RUSAGE_BOTH, ru);
 575                                 retval = p->pid;
 576                                 goto end_wait4;
 577                         case TASK_ZOMBIE:
 578                                 current->cutime += p->utime + p->cutime;
 579                                 current->cstime += p->stime + p->cstime;
 580                                 if (ru != NULL)
 581                                         getrusage(p, RUSAGE_BOTH, ru);
 582                                 flag = p->pid;
 583                                 if (stat_addr)
 584                                         put_user(p->exit_code, stat_addr);
 585                                 if (p->p_opptr != p->p_pptr) {
 586                                         REMOVE_LINKS(p);
 587                                         p->p_pptr = p->p_opptr;
 588                                         SET_LINKS(p);
 589                                         notify_parent(p);
 590                                 } else
 591                                         release(p);
 592 #ifdef DEBUG_PROC_TREE
 593                                 audit_ptree();
 594 #endif
 595                                 retval = flag;
 596                                 goto end_wait4;
 597                         default:
 598                                 continue;
 599                 }
 600         }
 601         if (flag) {
 602                 retval = 0;
 603                 if (options & WNOHANG)
 604                         goto end_wait4;
 605                 current->state=TASK_INTERRUPTIBLE;
 606                 schedule();
 607                 current->signal &= ~(1<<(SIGCHLD-1));
 608                 retval = -ERESTARTSYS;
 609                 if (current->signal & ~current->blocked)
 610                         goto end_wait4;
 611                 goto repeat;
 612         }
 613         retval = -ECHILD;
 614 end_wait4:
 615         remove_wait_queue(&current->wait_chldexit,&wait);
 616         return retval;
 617 }
 618 
 619 /*
 620  * sys_waitpid() remains for compatibility. waitpid() should be
 621  * implemented by calling sys_wait4() from libc.a.
 622  */
 623 asmlinkage int sys_waitpid(pid_t pid,unsigned int * stat_addr, int options)
     /*  */
 624 {
 625         return sys_wait4(pid, stat_addr, options, NULL);
 626 }
/* */
root/kernel/exit.c

DEFINITIONS
