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

DEFINITIONS
