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
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 #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 extern void shm_exit (void);
  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->uid != p->uid) && !suser())
  51                 return -EPERM;
  52         if (!sig)
  53                 return 0;
  54         if ((sig == SIGKILL) || (sig == SIGCONT)) {
  55                 if (p->state == TASK_STOPPED)
  56                         p->state = TASK_RUNNING;
  57                 p->exit_code = 0;
  58                 p->signal &= ~( (1<<(SIGSTOP-1)) | (1<<(SIGTSTP-1)) |
  59                                 (1<<(SIGTTIN-1)) | (1<<(SIGTTOU-1)) );
  60         }
  61         /* Depends on order SIGSTOP, SIGTSTP, SIGTTIN, SIGTTOU */
  62         if ((sig >= SIGSTOP) && (sig <= SIGTTOU)) 
  63                 p->signal &= ~(1<<(SIGCONT-1));
  64         /* Actually generate the signal */
  65         generate(sig,p);
  66         return 0;
  67 }
  68 
  69 void notify_parent(struct task_struct * tsk)
     /*  */
  70 {
  71         if (tsk->p_pptr == task[1])
  72                 tsk->exit_signal = SIGCHLD;
  73         send_sig(tsk->exit_signal, tsk->p_pptr, 1);
  74         wake_up_interruptible(&tsk->p_pptr->wait_chldexit);
  75 }
  76 
  77 void release(struct task_struct * p)
     /*  */
  78 {
  79         int i;
  80 
  81         if (!p)
  82                 return;
  83         if (p == current) {
  84                 printk("task releasing itself\n");
  85                 return;
  86         }
  87         for (i=1 ; i<NR_TASKS ; i++)
  88                 if (task[i] == p) {
  89                         task[i] = NULL;
  90                         REMOVE_LINKS(p);
  91                         free_page(p->kernel_stack_page);
  92                         free_page((long) p);
  93                         return;
  94                 }
  95         panic("trying to release non-existent task");
  96 }
  97 
  98 #ifdef DEBUG_PROC_TREE
  99 /*
 100  * Check to see if a task_struct pointer is present in the task[] array
 101  * Return 0 if found, and 1 if not found.
 102  */
 103 int bad_task_ptr(struct task_struct *p)
     /*  */
 104 {
 105         int     i;
 106 
 107         if (!p)
 108                 return 0;
 109         for (i=0 ; i<NR_TASKS ; i++)
 110                 if (task[i] == p)
 111                         return 0;
 112         return 1;
 113 }
 114         
 115 /*
 116  * This routine scans the pid tree and make sure the rep invarient still
 117  * holds.  Used for debugging only, since it's very slow....
 118  *
 119  * It looks a lot scarier than it really is.... we're doing nothing more
 120  * than verifying the doubly-linked list found in p_ysptr and p_osptr, 
 121  * and checking it corresponds with the process tree defined by p_cptr and 
 122  * p_pptr;
 123  */
 124 void audit_ptree(void)
     /*  */
 125 {
 126         int     i;
 127 
 128         for (i=1 ; i<NR_TASKS ; i++) {
 129                 if (!task[i])
 130                         continue;
 131                 if (bad_task_ptr(task[i]->p_pptr))
 132                         printk("Warning, pid %d's parent link is bad\n",
 133                                 task[i]->pid);
 134                 if (bad_task_ptr(task[i]->p_cptr))
 135                         printk("Warning, pid %d's child link is bad\n",
 136                                 task[i]->pid);
 137                 if (bad_task_ptr(task[i]->p_ysptr))
 138                         printk("Warning, pid %d's ys link is bad\n",
 139                                 task[i]->pid);
 140                 if (bad_task_ptr(task[i]->p_osptr))
 141                         printk("Warning, pid %d's os link is bad\n",
 142                                 task[i]->pid);
 143                 if (task[i]->p_pptr == task[i])
 144                         printk("Warning, pid %d parent link points to self\n",
 145                                 task[i]->pid);
 146                 if (task[i]->p_cptr == task[i])
 147                         printk("Warning, pid %d child link points to self\n",
 148                                 task[i]->pid);
 149                 if (task[i]->p_ysptr == task[i])
 150                         printk("Warning, pid %d ys link points to self\n",
 151                                 task[i]->pid);
 152                 if (task[i]->p_osptr == task[i])
 153                         printk("Warning, pid %d os link points to self\n",
 154                                 task[i]->pid);
 155                 if (task[i]->p_osptr) {
 156                         if (task[i]->p_pptr != task[i]->p_osptr->p_pptr)
 157                                 printk(
 158                         "Warning, pid %d older sibling %d parent is %d\n",
 159                                 task[i]->pid, task[i]->p_osptr->pid,
 160                                 task[i]->p_osptr->p_pptr->pid);
 161                         if (task[i]->p_osptr->p_ysptr != task[i])
 162                                 printk(
 163                 "Warning, pid %d older sibling %d has mismatched ys link\n",
 164                                 task[i]->pid, task[i]->p_osptr->pid);
 165                 }
 166                 if (task[i]->p_ysptr) {
 167                         if (task[i]->p_pptr != task[i]->p_ysptr->p_pptr)
 168                                 printk(
 169                         "Warning, pid %d younger sibling %d parent is %d\n",
 170                                 task[i]->pid, task[i]->p_osptr->pid,
 171                                 task[i]->p_osptr->p_pptr->pid);
 172                         if (task[i]->p_ysptr->p_osptr != task[i])
 173                                 printk(
 174                 "Warning, pid %d younger sibling %d has mismatched os link\n",
 175                                 task[i]->pid, task[i]->p_ysptr->pid);
 176                 }
 177                 if (task[i]->p_cptr) {
 178                         if (task[i]->p_cptr->p_pptr != task[i])
 179                                 printk(
 180                         "Warning, pid %d youngest child %d has mismatched parent link\n",
 181                                 task[i]->pid, task[i]->p_cptr->pid);
 182                         if (task[i]->p_cptr->p_ysptr)
 183                                 printk(
 184                         "Warning, pid %d youngest child %d has non-NULL ys link\n",
 185                                 task[i]->pid, task[i]->p_cptr->pid);
 186                 }
 187         }
 188 }
 189 #endif /* DEBUG_PROC_TREE */
 190 
 191 /*
 192  * This checks not only the pgrp, but falls back on the pid if no
 193  * satisfactory prgp is found. I dunno - gdb doesn't work correctly
 194  * without this...
 195  */
 196 int session_of_pgrp(int pgrp)
     /*  */
 197 {
 198         struct task_struct *p;
 199         int fallback;
 200 
 201         fallback = -1;
 202         for_each_task(p) {
 203                 if (p->session <= 0)
 204                         continue;
 205                 if (p->pgrp == pgrp)
 206                         return p->session;
 207                 if (p->pid == pgrp)
 208                         fallback = p->session;
 209         }
 210         return fallback;
 211 }
 212 
 213 /*
 214  * kill_pg() sends a signal to a process group: this is what the tty
 215  * control characters do (^C, ^Z etc)
 216  */
 217 int kill_pg(int pgrp, int sig, int priv)
     /*  */
 218 {
 219         struct task_struct *p;
 220         int err,retval = -ESRCH;
 221         int found = 0;
 222 
 223         if (sig<0 || sig>32 || pgrp<=0)
 224                 return -EINVAL;
 225         for_each_task(p) {
 226                 if (p->pgrp == pgrp) {
 227                         if ((err = send_sig(sig,p,priv)) != 0)
 228                                 retval = err;
 229                         else
 230                                 found++;
 231                 }
 232         }
 233         return(found ? 0 : retval);
 234 }
 235 
 236 /*
 237  * kill_sl() sends a signal to the session leader: this is used
 238  * to send SIGHUP to the controlling process of a terminal when
 239  * the connection is lost.
 240  */
 241 int kill_sl(int sess, int sig, int priv)
     /*  */
 242 {
 243         struct task_struct *p;
 244         int err,retval = -ESRCH;
 245         int found = 0;
 246 
 247         if (sig<0 || sig>32 || sess<=0)
 248                 return -EINVAL;
 249         for_each_task(p) {
 250                 if (p->session == sess && p->leader) {
 251                         if ((err = send_sig(sig,p,priv)) != 0)
 252                                 retval = err;
 253                         else
 254                                 found++;
 255                 }
 256         }
 257         return(found ? 0 : retval);
 258 }
 259 
 260 int kill_proc(int pid, int sig, int priv)
     /*  */
 261 {
 262         struct task_struct *p;
 263 
 264         if (sig<0 || sig>32)
 265                 return -EINVAL;
 266         for_each_task(p) {
 267                 if (p && p->pid == pid)
 268                         return send_sig(sig,p,priv);
 269         }
 270         return(-ESRCH);
 271 }
 272 
 273 /*
 274  * POSIX specifies that kill(-1,sig) is unspecified, but what we have
 275  * is probably wrong.  Should make it like BSD or SYSV.
 276  */
 277 asmlinkage int sys_kill(int pid,int sig)
     /*  */
 278 {
 279         int err, retval = 0, count = 0;
 280 
 281         if (!pid)
 282                 return(kill_pg(current->pgrp,sig,0));
 283         if (pid == -1) {
 284                 struct task_struct * p;
 285                 for_each_task(p) {
 286                         if (p->pid > 1 && p != current) {
 287                                 ++count;
 288                                 if ((err = send_sig(sig,p,0)) != -EPERM)
 289                                         retval = err;
 290                         }
 291                 }
 292                 return(count ? retval : -ESRCH);
 293         }
 294         if (pid < 0) 
 295                 return(kill_pg(-pid,sig,0));
 296         /* Normal kill */
 297         return(kill_proc(pid,sig,0));
 298 }
 299 
 300 /*
 301  * Determine if a process group is "orphaned", according to the POSIX
 302  * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 303  * by terminal-generated stop signals.  Newly orphaned process groups are 
 304  * to receive a SIGHUP and a SIGCONT.
 305  * 
 306  * "I ask you, have you ever known what it is to be an orphan?"
 307  */
 308 int is_orphaned_pgrp(int pgrp)
     /*  */
 309 {
 310         struct task_struct *p;
 311 
 312         for_each_task(p) {
 313                 if ((p->pgrp != pgrp) || 
 314                     (p->state == TASK_ZOMBIE) ||
 315                     (p->p_pptr->pid == 1))
 316                         continue;
 317                 if ((p->p_pptr->pgrp != pgrp) &&
 318                     (p->p_pptr->session == p->session))
 319                         return 0;
 320         }
 321         return(1);      /* (sighing) "Often!" */
 322 }
 323 
 324 static int has_stopped_jobs(int pgrp)
     /*  */
 325 {
 326         struct task_struct * p;
 327 
 328         for_each_task(p) {
 329                 if (p->pgrp != pgrp)
 330                         continue;
 331                 if (p->state == TASK_STOPPED)
 332                         return(1);
 333         }
 334         return(0);
 335 }
 336 
 337 static void forget_original_parent(struct task_struct * father)
     /*  */
 338 {
 339         struct task_struct * p;
 340 
 341         for_each_task(p) {
 342                 if (p->p_opptr == father)
 343                         if (task[1])
 344                                 p->p_opptr = task[1];
 345                         else
 346                                 p->p_opptr = task[0];
 347         }
 348 }
 349 
 350 volatile void do_exit(long code)
     /*  */
 351 {
 352         struct task_struct *p;
 353         int i;
 354 
 355 fake_volatile:
 356         if (current->semun)
 357                 sem_exit();
 358         if (current->shm)
 359                 shm_exit();
 360         free_page_tables(current);
 361         for (i=0 ; i<NR_OPEN ; i++)
 362                 if (current->filp[i])
 363                         sys_close(i);
 364         forget_original_parent(current);
 365         iput(current->pwd);
 366         current->pwd = NULL;
 367         iput(current->root);
 368         current->root = NULL;
 369         iput(current->executable);
 370         current->executable = NULL;
 371         /* Release all of the old mmap stuff. */
 372         
 373         {
 374                 struct vm_area_struct * mpnt, *mpnt1;
 375                 mpnt = current->mmap;
 376                 current->mmap = NULL;
 377                 while (mpnt) {
 378                         mpnt1 = mpnt->vm_next;
 379                         if (mpnt->vm_ops && mpnt->vm_ops->close)
 380                                 mpnt->vm_ops->close(mpnt);
 381                         kfree(mpnt);
 382                         mpnt = mpnt1;
 383                 }
 384         }
 385 
 386         if (current->ldt) {
 387                 free_page((unsigned long) current->ldt);
 388                 current->ldt = NULL;
 389                 for (i=1 ; i<NR_TASKS ; i++) {
 390                         if (task[i] == current) {
 391                                 set_ldt_desc(gdt+(i<<1)+FIRST_LDT_ENTRY, &default_ldt, 1);
 392                                 load_ldt(i);
 393                         }
 394                 }
 395         }
 396 
 397         current->state = TASK_ZOMBIE;
 398         current->exit_code = code;
 399         current->rss = 0;
 400         /* 
 401          * Check to see if any process groups have become orphaned
 402          * as a result of our exiting, and if they have any stopped
 403          * jobs, send them a SIGUP and then a SIGCONT.  (POSIX 3.2.2.2)
 404          *
 405          * Case i: Our father is in a different pgrp than we are
 406          * and we were the only connection outside, so our pgrp
 407          * is about to become orphaned.
 408          */
 409         if ((current->p_pptr->pgrp != current->pgrp) &&
 410             (current->p_pptr->session == current->session) &&
 411             is_orphaned_pgrp(current->pgrp) &&
 412             has_stopped_jobs(current->pgrp)) {
 413                 kill_pg(current->pgrp,SIGHUP,1);
 414                 kill_pg(current->pgrp,SIGCONT,1);
 415         }
 416         /* Let father know we died */
 417         notify_parent(current);
 418         
 419         /*
 420          * This loop does two things:
 421          * 
 422          * A.  Make init inherit all the child processes
 423          * B.  Check to see if any process groups have become orphaned
 424          *      as a result of our exiting, and if they have any stopped
 425          *      jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)
 426          */
 427         while ((p = current->p_cptr) != NULL) {
 428                 current->p_cptr = p->p_osptr;
 429                 p->p_ysptr = NULL;
 430                 p->flags &= ~(PF_PTRACED|PF_TRACESYS);
 431                 if (task[1])
 432                         p->p_pptr = task[1];
 433                 else
 434                         p->p_pptr = task[0];
 435                 p->p_osptr = p->p_pptr->p_cptr;
 436                 p->p_osptr->p_ysptr = p;
 437                 p->p_pptr->p_cptr = p;
 438                 if (p->state == TASK_ZOMBIE)
 439                         notify_parent(p);
 440                 /*
 441                  * process group orphan check
 442                  * Case ii: Our child is in a different pgrp 
 443                  * than we are, and it was the only connection
 444                  * outside, so the child pgrp is now orphaned.
 445                  */
 446                 if ((p->pgrp != current->pgrp) &&
 447                     (p->session == current->session) &&
 448                     is_orphaned_pgrp(p->pgrp) &&
 449                     has_stopped_jobs(p->pgrp)) {
 450                         kill_pg(p->pgrp,SIGHUP,1);
 451                         kill_pg(p->pgrp,SIGCONT,1);
 452                 }
 453         }
 454         if (current->leader) {
 455                 struct task_struct *p;
 456                 struct tty_struct *tty;
 457 
 458                 if (current->tty >= 0) {
 459                         tty = TTY_TABLE(current->tty);
 460                         if (tty) {
 461                                 if (tty->pgrp > 0)
 462                                         kill_pg(tty->pgrp, SIGHUP, 1);
 463                                 tty->pgrp = -1;
 464                                 tty->session = 0;
 465                         }
 466                 }
 467                 for_each_task(p) {
 468                         if (p->session == current->session)
 469                                 p->tty = -1;
 470                 }
 471         }
 472         if (last_task_used_math == current)
 473                 last_task_used_math = NULL;
 474 #ifdef DEBUG_PROC_TREE
 475         audit_ptree();
 476 #endif
 477         schedule();
 478 /*
 479  * In order to get rid of the "volatile function does return" message
 480  * I did this little loop that confuses gcc to think do_exit really
 481  * is volatile. In fact it's schedule() that is volatile in some
 482  * circumstances: when current->state = ZOMBIE, schedule() never
 483  * returns.
 484  *
 485  * In fact the natural way to do all this is to have the label and the
 486  * goto right after each other, but I put the fake_volatile label at
 487  * the start of the function just in case something /really/ bad
 488  * happens, and the schedule returns. This way we can try again. I'm
 489  * not paranoid: it's just that everybody is out to get me.
 490  */
 491         goto fake_volatile;
 492 }
 493 
 494 asmlinkage int sys_exit(int error_code)
     /*  */
 495 {
 496         do_exit((error_code&0xff)<<8);
 497 }
 498 
 499 asmlinkage int sys_wait4(pid_t pid,unsigned long * stat_addr, int options, struct rusage * ru)
     /*  */
 500 {
 501         int flag, retval;
 502         struct wait_queue wait = { current, NULL };
 503         struct task_struct *p;
 504 
 505         if (stat_addr) {
 506                 flag = verify_area(VERIFY_WRITE, stat_addr, 4);
 507                 if (flag)
 508                         return flag;
 509         }
 510         add_wait_queue(&current->wait_chldexit,&wait);
 511 repeat:
 512         flag=0;
 513         for (p = current->p_cptr ; p ; p = p->p_osptr) {
 514                 if (pid>0) {
 515                         if (p->pid != pid)
 516                                 continue;
 517                 } else if (!pid) {
 518                         if (p->pgrp != current->pgrp)
 519                                 continue;
 520                 } else if (pid != -1) {
 521                         if (p->pgrp != -pid)
 522                                 continue;
 523                 }
 524                 /* wait for cloned processes iff the __WCLONE flag is set */
 525                 if ((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
 526                         continue;
 527                 flag = 1;
 528                 switch (p->state) {
 529                         case TASK_STOPPED:
 530                                 if (!p->exit_code)
 531                                         continue;
 532                                 if (!(options & WUNTRACED) && !(p->flags & PF_PTRACED))
 533                                         continue;
 534                                 if (stat_addr)
 535                                         put_fs_long((p->exit_code << 8) | 0x7f,
 536                                                 stat_addr);
 537                                 p->exit_code = 0;
 538                                 if (ru != NULL)
 539                                         getrusage(p, RUSAGE_BOTH, ru);
 540                                 retval = p->pid;
 541                                 goto end_wait4;
 542                         case TASK_ZOMBIE:
 543                                 current->cutime += p->utime + p->cutime;
 544                                 current->cstime += p->stime + p->cstime;
 545                                 current->cmin_flt += p->min_flt + p->cmin_flt;
 546                                 current->cmaj_flt += p->maj_flt + p->cmaj_flt;
 547                                 if (ru != NULL)
 548                                         getrusage(p, RUSAGE_BOTH, ru);
 549                                 flag = p->pid;
 550                                 if (stat_addr)
 551                                         put_fs_long(p->exit_code, stat_addr);
 552                                 if (p->p_opptr != p->p_pptr) {
 553                                         REMOVE_LINKS(p);
 554                                         p->p_pptr = p->p_opptr;
 555                                         SET_LINKS(p);
 556                                         notify_parent(p);
 557                                 } else
 558                                         release(p);
 559 #ifdef DEBUG_PROC_TREE
 560                                 audit_ptree();
 561 #endif
 562                                 retval = flag;
 563                                 goto end_wait4;
 564                         default:
 565                                 continue;
 566                 }
 567         }
 568         if (flag) {
 569                 retval = 0;
 570                 if (options & WNOHANG)
 571                         goto end_wait4;
 572                 current->state=TASK_INTERRUPTIBLE;
 573                 schedule();
 574                 current->signal &= ~(1<<(SIGCHLD-1));
 575                 retval = -ERESTARTSYS;
 576                 if (current->signal & ~current->blocked)
 577                         goto end_wait4;
 578                 goto repeat;
 579         }
 580         retval = -ECHILD;
 581 end_wait4:
 582         remove_wait_queue(&current->wait_chldexit,&wait);
 583         return retval;
 584 }
 585 
 586 /*
 587  * sys_waitpid() remains for compatibility. waitpid() should be
 588  * implemented by calling sys_wait4() from libc.a.
 589  */
 590 asmlinkage int sys_waitpid(pid_t pid,unsigned long * stat_addr, int options)
     /*  */
 591 {
 592         return sys_wait4(pid, stat_addr, options, NULL);
 593 }
/* */
root/kernel/exit.c

DEFINITIONS
