about summary refs log tree commit diff
path: root/linuxthreads/manager.c
blob: d14a57ccd7b5821b619b6a6721c7c7b4df9cf980 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
/* Linuxthreads - a simple clone()-based implementation of Posix        */
/* threads for Linux.                                                   */
/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
/*                                                                      */
/* This program is free software; you can redistribute it and/or        */
/* modify it under the terms of the GNU Library General Public License  */
/* as published by the Free Software Foundation; either version 2       */
/* of the License, or (at your option) any later version.               */
/*                                                                      */
/* This program is distributed in the hope that it will be useful,      */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
/* GNU Library General Public License for more details.                 */

/* The "thread manager" thread: manages creation and termination of threads */

#include <errno.h>
#include <sched.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/poll.h>		/* for poll */
#include <sys/mman.h>           /* for mmap */
#include <sys/time.h>
#include <sys/wait.h>           /* for waitpid macros */
#include <linux/tasks.h>

#include "pthread.h"
#include "internals.h"
#include "spinlock.h"
#include "restart.h"
#include "semaphore.h"

/* Array of active threads. Entry 0 is reserved for the initial thread. */
struct pthread_handle_struct __pthread_handles[PTHREAD_THREADS_MAX] =
{ { LOCK_INITIALIZER, &__pthread_initial_thread, 0}, /* All NULLs */ };

/* Indicate whether at least one thread has a user-defined stack (if 1),
   or if all threads have stacks supplied by LinuxThreads (if 0). */
int __pthread_nonstandard_stacks = 0;

/* Number of active entries in __pthread_handles (used by gdb) */
volatile int __pthread_handles_num = 1;

/* Whether to use debugger additional actions for thread creation
   (set to 1 by gdb) */
volatile int __pthread_threads_debug = 0;

/* Mapping from stack segment to thread descriptor. */
/* Stack segment numbers are also indices into the __pthread_handles array. */
/* Stack segment number 0 is reserved for the initial thread. */

static inline pthread_descr thread_segment(int seg)
{
  return (pthread_descr)(THREAD_STACK_START_ADDRESS - (seg - 1) * STACK_SIZE)
         - 1;
}

/* Flag set in signal handler to record child termination */

static volatile int terminated_children = 0;

/* Flag set when the initial thread is blocked on pthread_exit waiting
   for all other threads to terminate */

static int main_thread_exiting = 0;

/* Counter used to generate unique thread identifier.
   Thread identifier is pthread_threads_counter + segment. */

static pthread_t pthread_threads_counter = 0;

/* Forward declarations */

static int pthread_handle_create(pthread_t *thread, const pthread_attr_t *attr,
                                 void * (*start_routine)(void *), void *arg,
                                 sigset_t *mask, int father_pid);
static void pthread_handle_free(pthread_t th_id);
static void pthread_handle_exit(pthread_descr issuing_thread, int exitcode);
static void pthread_reap_children(void);
static void pthread_kill_all_threads(int sig, int main_thread_also);

/* The server thread managing requests for thread creation and termination */

int __pthread_manager(void *arg)
{
  int reqfd = (int)arg;
  struct pollfd ufd;
  sigset_t mask;
  int n;
  struct pthread_request request;

  /* If we have special thread_self processing, initialize it.  */
#ifdef INIT_THREAD_SELF
  INIT_THREAD_SELF(&__pthread_manager_thread);
#endif
  /* Set the error variable.  */
  __pthread_manager_thread.p_errnop = &__pthread_manager_thread.p_errno;
  __pthread_manager_thread.p_h_errnop = &__pthread_manager_thread.p_h_errno;
  /* Block all signals except PTHREAD_SIG_RESTART, PTHREAD_SIG_CANCEL
     and SIGTRAP */
  sigfillset(&mask);
  sigdelset(&mask, PTHREAD_SIG_RESTART);
  sigdelset(&mask, PTHREAD_SIG_CANCEL); /* for debugging new threads */
  sigdelset(&mask, SIGTRAP);            /* for debugging purposes */
  sigprocmask(SIG_SETMASK, &mask, NULL);
  /* Raise our priority to match that of main thread */
  __pthread_manager_adjust_prio(__pthread_main_thread->p_priority);
  /* Synchronize debugging of the thread manager */
  n = __libc_read(reqfd, (char *)&request, sizeof(request));
  ASSERT(n == sizeof(request) && request.req_kind == REQ_DEBUG);
  ufd.fd = reqfd;
  ufd.events = POLLIN;
  /* Enter server loop */
  while(1) {
    n = __poll(&ufd, 1, 2000);

    /* Check for termination of the main thread */
    if (getppid() == 1) {
      pthread_kill_all_threads(SIGKILL, 0);
      _exit(0);
    }
    /* Check for dead children */
    if (terminated_children) {
      terminated_children = 0;
      pthread_reap_children();
    }
    /* Read and execute request */
    if (n == 1 && (ufd.revents & POLLIN)) {
      n = __libc_read(reqfd, (char *)&request, sizeof(request));
      ASSERT(n == sizeof(request));
      switch(request.req_kind) {
      case REQ_CREATE:
        request.req_thread->p_retcode =
          pthread_handle_create((pthread_t *) &request.req_thread->p_retval,
                                request.req_args.create.attr,
                                request.req_args.create.fn,
                                request.req_args.create.arg,
                                &request.req_args.create.mask,
                                request.req_thread->p_pid);
        restart(request.req_thread);
        break;
      case REQ_FREE:
	pthread_handle_free(request.req_args.free.thread_id);
        break;
      case REQ_PROCESS_EXIT:
        pthread_handle_exit(request.req_thread,
                            request.req_args.exit.code);
        break;
      case REQ_MAIN_THREAD_EXIT:
        main_thread_exiting = 1;
        if (__pthread_main_thread->p_nextlive == __pthread_main_thread) {
          restart(__pthread_main_thread);
          return 0;
        }
        break;
      case REQ_POST:
        sem_post(request.req_args.post);
        break;
      case REQ_DEBUG:
        /* Make gdb aware of new thread */
        if (__pthread_threads_debug) raise(PTHREAD_SIG_CANCEL);
        restart(request.req_thread);
        break;
      }
    }
  }
}

/* Process creation */

static int pthread_start_thread(void *arg)
{
  pthread_descr self = (pthread_descr) arg;
  struct pthread_request request;
  void * outcome;
  /* Initialize special thread_self processing, if any.  */
#ifdef INIT_THREAD_SELF
  INIT_THREAD_SELF(self);
#endif
  /* Make sure our pid field is initialized, just in case we get there
     before our father has initialized it. */
  self->p_pid = __getpid();
  /* Initial signal mask is that of the creating thread. (Otherwise,
     we'd just inherit the mask of the thread manager.) */
  sigprocmask(SIG_SETMASK, &self->p_start_args.mask, NULL);
  /* Set the scheduling policy and priority for the new thread, if needed */
  if (self->p_start_args.schedpolicy >= 0)
    __sched_setscheduler(self->p_pid, self->p_start_args.schedpolicy,
                         &self->p_start_args.schedparam);
  /* Make gdb aware of new thread */
  if (__pthread_threads_debug) {
    request.req_thread = self;
    request.req_kind = REQ_DEBUG;
    __libc_write(__pthread_manager_request,
                 (char *) &request, sizeof(request));
    suspend(self);
  }
  /* Run the thread code */
  outcome = self->p_start_args.start_routine(self->p_start_args.arg);
  /* Exit with the given return value */
  pthread_exit(outcome);
  return 0;
}

static int pthread_handle_create(pthread_t *thread, const pthread_attr_t *attr,
				 void * (*start_routine)(void *), void *arg,
				 sigset_t * mask, int father_pid)
{
  size_t sseg;
  int pid;
  pthread_descr new_thread;
  char * new_thread_bottom;
  pthread_t new_thread_id;
  void *guardaddr = NULL;
  size_t guardsize = 0;

  /* First check whether we have to change the policy and if yes, whether
     we can  do this.  Normally this should be done by examining the
     return value of the __sched_setscheduler call in pthread_start_thread
     but this is hard to implement.  FIXME  */
  if (attr != NULL && attr->schedpolicy != SCHED_OTHER && geteuid () != 0)
    return EPERM;
  /* Find a free stack segment for the current stack */
  for (sseg = 1; ; sseg++)
    {
      if (sseg >= PTHREAD_THREADS_MAX)
	return EAGAIN;
      if (__pthread_handles[sseg].h_descr != NULL)
	continue;

      if (attr == NULL || !attr->stackaddr_set)
	{
	  new_thread = thread_segment(sseg);
	  new_thread_bottom = (char *) new_thread - STACK_SIZE;
	  /* Allocate space for stack and thread descriptor. */
	  if (mmap((caddr_t)((char *)(new_thread+1) - INITIAL_STACK_SIZE),
		   INITIAL_STACK_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
		   MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED | MAP_GROWSDOWN,
		   -1, 0) != MAP_FAILED)
	    {
	      /* We manage to get a stack.  Now see whether we need a guard
		 and allocate it if necessary.  */
	      if (attr == NULL || attr->guardsize != 0)
		{
		  guardsize = attr ? attr->guardsize : __getpagesize ();
		  guardaddr = mmap ((caddr_t)((char *)(new_thread+1)
					      - STACK_SIZE),
				    guardsize, 0, MAP_FIXED, -1, 0);
		  if (guardaddr == MAP_FAILED)
		    {
		      /* We don't make this an error.  */
		      guardaddr = NULL;
		      guardsize = 0;
		    }
		}
	      break;
	    }
	  /* It seems part of this segment is already mapped. Try the next. */
	}
      else
	{
	  new_thread = (pthread_descr) ((long) attr->stackaddr
					& -sizeof(void *)) - 1;
	  new_thread_bottom = (char *) attr->stackaddr - attr->stacksize;
	  break;
	}
    }
  /* Allocate new thread identifier */
  pthread_threads_counter += PTHREAD_THREADS_MAX;
  new_thread_id = sseg + pthread_threads_counter;
  /* Initialize the thread descriptor */
  new_thread->p_nextwaiting = NULL;
  new_thread->p_tid = new_thread_id;
  new_thread->p_priority = 0;
  new_thread->p_lock = &(__pthread_handles[sseg].h_lock);
  new_thread->p_signal = 0;
  new_thread->p_signal_jmp = NULL;
  new_thread->p_cancel_jmp = NULL;
  new_thread->p_terminated = 0;
  new_thread->p_detached = attr == NULL ? 0 : attr->detachstate;
  new_thread->p_exited = 0;
  new_thread->p_retval = NULL;
  new_thread->p_joining = NULL;
  new_thread->p_cleanup = NULL;
  new_thread->p_cancelstate = PTHREAD_CANCEL_ENABLE;
  new_thread->p_canceltype = PTHREAD_CANCEL_DEFERRED;
  new_thread->p_canceled = 0;
  new_thread->p_errnop = &new_thread->p_errno;
  new_thread->p_errno = 0;
  new_thread->p_h_errnop = &new_thread->p_h_errno;
  new_thread->p_h_errno = 0;
  new_thread->p_in_sighandler = NULL;
  new_thread->p_sigwaiting = 0;
  new_thread->p_guardaddr = guardaddr;
  new_thread->p_guardsize = guardsize;
  new_thread->p_userstack = attr != NULL && attr->stackaddr_set;
  memset (new_thread->p_specific, '\0',
	  PTHREAD_KEY_1STLEVEL_SIZE * sizeof (new_thread->p_specific[0]));
  /* Initialize the thread handle */
  __pthread_init_lock(&__pthread_handles[sseg].h_lock);
  __pthread_handles[sseg].h_descr = new_thread;
  __pthread_handles[sseg].h_bottom = new_thread_bottom;
  /* Determine scheduling parameters for the thread */
  new_thread->p_start_args.schedpolicy = -1;
  if (attr != NULL) {
    switch(attr->inheritsched) {
    case PTHREAD_EXPLICIT_SCHED:
      new_thread->p_start_args.schedpolicy = attr->schedpolicy;
      memcpy (&new_thread->p_start_args.schedparam, &attr->schedparam,
	      sizeof (struct sched_param));
      break;
    case PTHREAD_INHERIT_SCHED:
      /* schedpolicy doesn't need to be set, only get priority */
      __sched_getparam(father_pid, &new_thread->p_start_args.schedparam);
      break;
    }
    new_thread->p_priority =
      new_thread->p_start_args.schedparam.sched_priority;
  }
  /* Finish setting up arguments to pthread_start_thread */
  new_thread->p_start_args.start_routine = start_routine;
  new_thread->p_start_args.arg = arg;
  new_thread->p_start_args.mask = *mask;
  /* Raise priority of thread manager if needed */
  __pthread_manager_adjust_prio(new_thread->p_priority);
  /* Do the cloning */
  pid = __clone(pthread_start_thread, (void **) new_thread,
                CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND |
                PTHREAD_SIG_RESTART,
                new_thread);
  /* Check if cloning succeeded */
  if (pid == -1) {
    /* Free the stack if we allocated it */
    if (attr == NULL || !attr->stackaddr_set)
      {
	munmap((caddr_t)((char *)(new_thread+1) - INITIAL_STACK_SIZE),
	       INITIAL_STACK_SIZE);
	if (new_thread->p_guardsize != 0)
	  munmap(new_thread->p_guardaddr, new_thread->p_guardsize);
      }
    __pthread_handles[sseg].h_descr = NULL;
    __pthread_handles[sseg].h_bottom = NULL;
    __pthread_handles_num--;
    return errno;
  }
  /* Insert new thread in doubly linked list of active threads */
  new_thread->p_prevlive = __pthread_main_thread;
  new_thread->p_nextlive = __pthread_main_thread->p_nextlive;
  __pthread_main_thread->p_nextlive->p_prevlive = new_thread;
  __pthread_main_thread->p_nextlive = new_thread;
  /* Set pid field of the new thread, in case we get there before the
     child starts. */
  new_thread->p_pid = pid;
  /* We're all set */
  *thread = new_thread_id;
  return 0;
}


/* Try to free the resources of a thread when requested by pthread_join
   or pthread_detach on a terminated thread. */

static void pthread_free(pthread_descr th)
{
  pthread_handle handle;
  ASSERT(th->p_exited);
  /* Make the handle invalid */
  handle =  thread_handle(th->p_tid);
  __pthread_lock(&handle->h_lock);
  handle->h_descr = NULL;
  handle->h_bottom = (char *)(-1L);
  __pthread_unlock(&handle->h_lock);
  /* One fewer threads in __pthread_handles */
  __pthread_handles_num--;
  /* If initial thread, nothing to free */
  if (th == &__pthread_initial_thread) return;
  if (!th->p_userstack)
    {
      /* Free the stack and thread descriptor area */
      if (th->p_guardsize != 0)
	munmap(th->p_guardaddr, th->p_guardsize);
      munmap((caddr_t) ((char *)(th+1) - STACK_SIZE), STACK_SIZE);
    }
}

/* Handle threads that have exited */

static void pthread_exited(pid_t pid)
{
  pthread_descr th;
  int detached;
  /* Find thread with that pid */
  for (th = __pthread_main_thread->p_nextlive;
       th != __pthread_main_thread;
       th = th->p_nextlive) {
    if (th->p_pid == pid) {
      /* Remove thread from list of active threads */
      th->p_nextlive->p_prevlive = th->p_prevlive;
      th->p_prevlive->p_nextlive = th->p_nextlive;
      /* Mark thread as exited, and if detached, free its resources */
      __pthread_lock(th->p_lock);
      th->p_exited = 1;
      detached = th->p_detached;
      __pthread_unlock(th->p_lock);
      if (detached)
	pthread_free(th);
      break;
    }
  }
  /* If all threads have exited and the main thread is pending on a
     pthread_exit, wake up the main thread and terminate ourselves. */
  if (main_thread_exiting &&
      __pthread_main_thread->p_nextlive == __pthread_main_thread) {
    restart(__pthread_main_thread);
    _exit(0);
  }
}

static void pthread_reap_children(void)
{
  pid_t pid;
  int status;

  while ((pid = __libc_waitpid(-1, &status, WNOHANG | __WCLONE)) > 0) {
    pthread_exited(pid);
    if (WIFSIGNALED(status)) {
      /* If a thread died due to a signal, send the same signal to
         all other threads, including the main thread. */
      pthread_kill_all_threads(WTERMSIG(status), 1);
      _exit(0);
    }
  }
}

/* Try to free the resources of a thread when requested by pthread_join
   or pthread_detach on a terminated thread. */

static void pthread_handle_free(pthread_t th_id)
{
  pthread_handle handle = thread_handle(th_id);
  pthread_descr th;

  __pthread_lock(&handle->h_lock);
  if (invalid_handle(handle, th_id)) {
    /* pthread_reap_children has deallocated the thread already,
       nothing needs to be done */
    __pthread_unlock(&handle->h_lock);
    return;
  }
  th = handle->h_descr;
  if (th->p_exited) {
    __pthread_unlock(&handle->h_lock);
    pthread_free(th);
  } else {
    /* The Unix process of the thread is still running.
       Mark the thread as detached so that the thread manager will
       deallocate its resources when the Unix process exits. */
    th->p_detached = 1;
    __pthread_unlock(&handle->h_lock);
  }
}

/* Send a signal to all running threads */

static void pthread_kill_all_threads(int sig, int main_thread_also)
{
  pthread_descr th;
  for (th = __pthread_main_thread->p_nextlive;
       th != __pthread_main_thread;
       th = th->p_nextlive) {
    kill(th->p_pid, sig);
  }
  if (main_thread_also) {
    kill(__pthread_main_thread->p_pid, sig);
  }
}

/* Process-wide exit() */

static void pthread_handle_exit(pthread_descr issuing_thread, int exitcode)
{
  pthread_descr th;
  __pthread_exit_requested = 1;
  __pthread_exit_code = exitcode;
  /* Send the CANCEL signal to all running threads, including the main
     thread, but excluding the thread from which the exit request originated
     (that thread must complete the exit, e.g. calling atexit functions
     and flushing stdio buffers). */
  for (th = issuing_thread->p_nextlive;
       th != issuing_thread;
       th = th->p_nextlive) {
    kill(th->p_pid, PTHREAD_SIG_CANCEL);
  }
  /* Now, wait for all these threads, so that they don't become zombies
     and their times are properly added to the thread manager's times. */
  for (th = issuing_thread->p_nextlive;
       th != issuing_thread;
       th = th->p_nextlive) {
    waitpid(th->p_pid, NULL, __WCLONE);
  }
  restart(issuing_thread);
  _exit(0);
}

/* Handler for PTHREAD_SIG_RESTART in thread manager thread */

void __pthread_manager_sighandler(int sig)
{
  terminated_children = 1;
}

/* Adjust priority of thread manager so that it always run at a priority
   higher than all threads */

void __pthread_manager_adjust_prio(int thread_prio)
{
  struct sched_param param;

  if (thread_prio <= __pthread_manager_thread.p_priority) return;
  param.sched_priority =
    thread_prio < __sched_get_priority_max(SCHED_FIFO)
    ? thread_prio + 1 : thread_prio;
  __sched_setscheduler(__pthread_manager_thread.p_pid, SCHED_FIFO, &param);
  __pthread_manager_thread.p_priority = thread_prio;
}