root/kernel/exit.c

/* */

DEFINITIONS

1. send_sig
2. release
3. bad_task_ptr
4. audit_ptree
5. session_of_pgrp
6. kill_pg
7. kill_sl
8. kill_proc
9. sys_kill
10. is_orphaned_pgrp
11. has_stopped_jobs
12. forget_original_parent
13. do_exit
14. sys_exit
15. sys_wait4
16. sys_waitpid

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

/* */