src/runtime/thread.c

   1 /*
   2  * This software is part of the SBCL system. See the README file for
   3  * more information.
   4  *
   5  * This software is derived from the CMU CL system, which was
   6  * written at Carnegie Mellon University and released into the
   7  * public domain. The software is in the public domain and is
   8  * provided with absolutely no warranty. See the COPYING and CREDITS
   9  * files for more information.
  10  */
  11
  12 #include "sbcl.h"
  13
  14 #include <stdlib.h>
  15 #include <stdio.h>
  16 #include <string.h>
  17 #ifndef LISP_FEATURE_WIN32
  18 #include <sched.h>
  19 #endif
  20 #include <signal.h>
  21 #include <stddef.h>
  22 #include <errno.h>
  23 #include <sys/types.h>
  24 #ifndef LISP_FEATURE_WIN32
  25 #include <sys/wait.h>
  26 #endif
  27
  28 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
  29 #include <mach/mach.h>
  30 #include <mach/mach_error.h>
  31 #include <mach/mach_types.h>
  32 #endif
  33
  34 #include "runtime.h"
  35 #include "validate.h"           /* for BINDING_STACK_SIZE etc */
  36 #include "alloc.h"
  37 #include "thread.h"
  38 #include "arch.h"
  39 #include "target-arch-os.h"
  40 #include "os.h"
  41 #include "globals.h"
  42 #include "dynbind.h"
  43 #include "genesis/cons.h"
  44 #include "genesis/fdefn.h"
  45 #include "interr.h"             /* for lose() */
  46 #include "gc-internal.h"
  47
  48 #ifdef LISP_FEATURE_WIN32
  49 /*
  50  * Win32 doesn't have SIGSTKSZ, and we're not switching stacks anyway,
  51  * so define it arbitrarily
  52  */
  53 #define SIGSTKSZ 1024
  54 #endif
  55
  56 #if defined(LISP_FEATURE_DARWIN) && defined(LISP_FEATURE_SB_THREAD)
  57 #define DELAY_THREAD_POST_MORTEM 5
  58 #define LOCK_CREATE_THREAD
  59 #endif
  60
  61 #ifdef LISP_FEATURE_FREEBSD
  62 #define CREATE_CLEANUP_THREAD
  63 #define LOCK_CREATE_THREAD
  64 #endif
  65
  66 #define ALIEN_STACK_SIZE (1*1024*1024) /* 1Mb size chosen at random */
  67
  68 #ifdef LISP_FEATURE_SB_THREAD
  69 struct thread_post_mortem {
  70 #ifdef DELAY_THREAD_POST_MORTEM
  71     struct thread_post_mortem *next;
  72 #endif
  73     os_thread_t os_thread;
  74     pthread_attr_t *os_attr;
  75     os_vm_address_t os_address;
  76 };
  77
  78 #ifdef DELAY_THREAD_POST_MORTEM
  79 static int pending_thread_post_mortem_count = 0;
  80 pthread_mutex_t thread_post_mortem_lock = PTHREAD_MUTEX_INITIALIZER;
  81 #endif
  82 static struct thread_post_mortem * volatile pending_thread_post_mortem = 0;
  83 #endif
  84
  85 int dynamic_values_bytes=TLS_SIZE*sizeof(lispobj);  /* same for all threads */
  86 struct thread *all_threads;
  87 extern struct interrupt_data * global_interrupt_data;
  88
  89 #ifdef LISP_FEATURE_SB_THREAD
  90 pthread_mutex_t all_threads_lock = PTHREAD_MUTEX_INITIALIZER;
  91 #ifdef LOCK_CREATE_THREAD
  92 static pthread_mutex_t create_thread_lock = PTHREAD_MUTEX_INITIALIZER;
  93 #endif
  94 #ifdef LISP_FEATURE_GCC_TLS
  95 __thread struct thread *current_thread;
  96 #endif
  97 #endif
  98
  99 #if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
 100 extern lispobj call_into_lisp_first_time(lispobj fun, lispobj *args, int nargs);
 101 #endif
 102
 103 static void
 104 link_thread(struct thread *th)
 105 {
 106     if (all_threads) all_threads->prev=th;
 107     th->next=all_threads;
 108     th->prev=0;
 109     all_threads=th;
 110 }
 111
 112 #ifdef LISP_FEATURE_SB_THREAD
 113 static void
 114 unlink_thread(struct thread *th)
 115 {
 116     if (th->prev)
 117         th->prev->next = th->next;
 118     else
 119         all_threads = th->next;
 120     if (th->next)
 121         th->next->prev = th->prev;
 122 }
 123 #endif
 124
 125 static int
 126 initial_thread_trampoline(struct thread *th)
 127 {
 128     lispobj function;
 129 #if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
 130     lispobj *args = NULL;
 131 #endif
 132     function = th->no_tls_value_marker;
 133     th->no_tls_value_marker = NO_TLS_VALUE_MARKER_WIDETAG;
 134     if(arch_os_thread_init(th)==0) return 1;
 135     link_thread(th);
 136     th->os_thread=thread_self();
 137 #ifndef LISP_FEATURE_WIN32
 138     protect_control_stack_guard_page(1);
 139 #endif
 140
 141 #if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
 142     return call_into_lisp_first_time(function,args,0);
 143 #else
 144     return funcall0(function);
 145 #endif
 146 }
 147
 148 #ifdef LISP_FEATURE_SB_THREAD
 149 #define THREAD_STATE_LOCK_SIZE \
 150     (sizeof(pthread_mutex_t))+(sizeof(pthread_cond_t))
 151 #else
 152 #define THREAD_STATE_LOCK_SIZE 0
 153 #endif
 154
 155 #define THREAD_STRUCT_SIZE (thread_control_stack_size + BINDING_STACK_SIZE + \
 156                             ALIEN_STACK_SIZE +                               \
 157                             THREAD_STATE_LOCK_SIZE +                         \
 158                             dynamic_values_bytes +                           \
 159                             32 * SIGSTKSZ +                                  \
 160                             THREAD_ALIGNMENT_BYTES)
 161
 162 #ifdef LISP_FEATURE_SB_THREAD
 163 /* THREAD POST MORTEM CLEANUP
 164  *
 165  * Memory allocated for the thread stacks cannot be reclaimed while
 166  * the thread is still alive, so we need a mechanism for post mortem
 167  * cleanups. FIXME: We actually have three, for historical reasons as
 168  * the saying goes. Do we really need three? Nikodemus guesses that
 169  * not anymore, now that we properly call pthread_attr_destroy before
 170  * freeing the stack. */
 171
 172 static struct thread_post_mortem *
 173 plan_thread_post_mortem(struct thread *corpse)
 174 {
 175     if (corpse) {
 176         struct thread_post_mortem *post_mortem = malloc(sizeof(struct thread_post_mortem));
 177         gc_assert(post_mortem);
 178         post_mortem->os_thread = corpse->os_thread;
 179         post_mortem->os_attr = corpse->os_attr;
 180         post_mortem->os_address = corpse->os_address;
 181 #ifdef DELAY_THREAD_POST_MORTEM
 182         post_mortem->next = NULL;
 183 #endif
 184         return post_mortem;
 185     } else {
 186         /* FIXME: When does this happen? */
 187         return NULL;
 188     }
 189 }
 190
 191 static void
 192 perform_thread_post_mortem(struct thread_post_mortem *post_mortem)
 193 {
 194 #ifdef CREATE_POST_MORTEM_THREAD
 195     pthread_detach(pthread_self());
 196 #endif
 197     if (post_mortem) {
 198         gc_assert(!pthread_join(post_mortem->os_thread, NULL));
 199         gc_assert(!pthread_attr_destroy(post_mortem->os_attr));
 200         free(post_mortem->os_attr);
 201         os_invalidate(post_mortem->os_address, THREAD_STRUCT_SIZE);
 202         free(post_mortem);
 203     }
 204 }
 205
 206 static void
 207 schedule_thread_post_mortem(struct thread *corpse)
 208 {
 209     struct thread_post_mortem *post_mortem = NULL;
 210     if (corpse) {
 211         post_mortem = plan_thread_post_mortem(corpse);
 212
 213 #ifdef DELAY_THREAD_POST_MORTEM
 214         pthread_mutex_lock(&thread_post_mortem_lock);
 215         /* First stick the new post mortem to the end of the queue. */
 216         if (pending_thread_post_mortem) {
 217             struct thread_post_mortem *next = pending_thread_post_mortem;
 218             while (next->next) {
 219                 next = next->next;
 220             }
 221             next->next = post_mortem;
 222         } else {
 223             pending_thread_post_mortem = post_mortem;
 224         }
 225         /* Then, if there are enough things in the queue, clean up one
 226          * from the head -- or increment the count, and null out the
 227          * post_mortem we have. */
 228         if (pending_thread_post_mortem_count > DELAY_THREAD_POST_MORTEM) {
 229             post_mortem = pending_thread_post_mortem;
 230             pending_thread_post_mortem = post_mortem->next;
 231         } else {
 232             pending_thread_post_mortem_count++;
 233             post_mortem = NULL;
 234         }
 235         pthread_mutex_unlock(&thread_post_mortem_lock);
 236         /* Finally run, the cleanup, if any. */
 237         perform_thread_post_mortem(post_mortem);
 238 #elif defined(CREATE_POST_MORTEM_THREAD)
 239         gc_assert(!pthread_create(&thread, NULL, perform_thread_post_mortem, post_mortem));
 240 #else
 241         post_mortem = (struct thread_post_mortem *)
 242             swap_lispobjs((lispobj *)(void *)&pending_thread_post_mortem,
 243                           (lispobj)post_mortem);
 244         perform_thread_post_mortem(post_mortem);
 245 #endif
 246     }
 247 }
 248
 249 /* this is the first thing that runs in the child (which is why the
 250  * silly calling convention).  Basically it calls the user's requested
 251  * lisp function after doing arch_os_thread_init and whatever other
 252  * bookkeeping needs to be done
 253  */
 254 int
 255 new_thread_trampoline(struct thread *th)
 256 {
 257     lispobj function;
 258     int result, lock_ret;
 259
 260     FSHOW((stderr,"/creating thread %lu\n", thread_self()));
 261     function = th->no_tls_value_marker;
 262     th->no_tls_value_marker = NO_TLS_VALUE_MARKER_WIDETAG;
 263     if(arch_os_thread_init(th)==0) {
 264         /* FIXME: handle error */
 265         lose("arch_os_thread_init failed\n");
 266     }
 267
 268     th->os_thread=thread_self();
 269     protect_control_stack_guard_page(1);
 270     /* Since GC can only know about this thread from the all_threads
 271      * list and we're just adding this thread to it there is no danger
 272      * of deadlocking even with SIG_STOP_FOR_GC blocked (which it is
 273      * not). */
 274     lock_ret = pthread_mutex_lock(&all_threads_lock);
 275     gc_assert(lock_ret == 0);
 276     link_thread(th);
 277     lock_ret = pthread_mutex_unlock(&all_threads_lock);
 278     gc_assert(lock_ret == 0);
 279
 280     result = funcall0(function);
 281
 282     /* Block GC */
 283     block_blockable_signals();
 284     set_thread_state(th, STATE_DEAD);
 285
 286     /* SIG_STOP_FOR_GC is blocked and GC might be waiting for this
 287      * thread, but since we are already dead it won't wait long. */
 288     lock_ret = pthread_mutex_lock(&all_threads_lock);
 289     gc_assert(lock_ret == 0);
 290
 291     gc_alloc_update_page_tables(BOXED_PAGE_FLAG, &th->alloc_region);
 292     unlink_thread(th);
 293     pthread_mutex_unlock(&all_threads_lock);
 294     gc_assert(lock_ret == 0);
 295
 296     if(th->tls_cookie>=0) arch_os_thread_cleanup(th);
 297     pthread_mutex_destroy(th->state_lock);
 298     pthread_cond_destroy(th->state_cond);
 299
 300     os_invalidate((os_vm_address_t)th->interrupt_data,
 301                   (sizeof (struct interrupt_data)));
 302
 303 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
 304     FSHOW((stderr, "Deallocating mach port %x\n", THREAD_STRUCT_TO_EXCEPTION_PORT(th)));
 305     mach_port_move_member(mach_task_self(),
 306                           THREAD_STRUCT_TO_EXCEPTION_PORT(th),
 307                           MACH_PORT_NULL);
 308     mach_port_deallocate(mach_task_self(),
 309                          THREAD_STRUCT_TO_EXCEPTION_PORT(th));
 310     mach_port_destroy(mach_task_self(),
 311                       THREAD_STRUCT_TO_EXCEPTION_PORT(th));
 312 #endif
 313
 314     schedule_thread_post_mortem(th);
 315     FSHOW((stderr,"/exiting thread %lu\n", thread_self()));
 316     return result;
 317 }
 318
 319 #endif /* LISP_FEATURE_SB_THREAD */
 320
 321 static void
 322 free_thread_struct(struct thread *th)
 323 {
 324     if (th->interrupt_data)
 325         os_invalidate((os_vm_address_t) th->interrupt_data,
 326                       (sizeof (struct interrupt_data)));
 327     os_invalidate((os_vm_address_t) th->os_address,
 328                   THREAD_STRUCT_SIZE);
 329 }
 330
 331 /* this is called from any other thread to create the new one, and
 332  * initialize all parts of it that can be initialized from another
 333  * thread
 334  */
 335
 336 static struct thread *
 337 create_thread_struct(lispobj initial_function) {
 338     union per_thread_data *per_thread;
 339     struct thread *th=0;        /*  subdue gcc */
 340     void *spaces=0;
 341     void *aligned_spaces=0;
 342 #ifdef LISP_FEATURE_SB_THREAD
 343     unsigned int i;
 344 #endif
 345
 346     /* May as well allocate all the spaces at once: it saves us from
 347      * having to decide what to do if only some of the allocations
 348      * succeed. SPACES must be appropriately aligned, since the GC
 349      * expects the control stack to start at a page boundary -- and
 350      * the OS may have even more rigorous requirements. We can't rely
 351      * on the alignment passed from os_validate, since that might
 352      * assume the current (e.g. 4k) pagesize, while we calculate with
 353      * the biggest (e.g. 64k) pagesize allowed by the ABI. */
 354     spaces=os_validate(0, THREAD_STRUCT_SIZE);
 355     if(!spaces)
 356         return NULL;
 357     /* Aligning up is safe as THREAD_STRUCT_SIZE has
 358      * THREAD_ALIGNMENT_BYTES padding. */
 359     aligned_spaces = (void *)((((unsigned long)(char *)spaces)
 360                                + THREAD_ALIGNMENT_BYTES-1)
 361                               &~(unsigned long)(THREAD_ALIGNMENT_BYTES-1));
 362     per_thread=(union per_thread_data *)
 363         (aligned_spaces+
 364          thread_control_stack_size+
 365          BINDING_STACK_SIZE+
 366          ALIEN_STACK_SIZE +
 367          THREAD_STATE_LOCK_SIZE);
 368
 369 #ifdef LISP_FEATURE_SB_THREAD
 370     for(i = 0; i < (dynamic_values_bytes / sizeof(lispobj)); i++)
 371         per_thread->dynamic_values[i] = NO_TLS_VALUE_MARKER_WIDETAG;
 372     if (all_threads == 0) {
 373         if(SymbolValue(FREE_TLS_INDEX,0)==UNBOUND_MARKER_WIDETAG) {
 374             SetSymbolValue
 375                 (FREE_TLS_INDEX,
 376                  /* FIXME: should be MAX_INTERRUPTS -1 ? */
 377                  make_fixnum(MAX_INTERRUPTS+
 378                              sizeof(struct thread)/sizeof(lispobj)),
 379                  0);
 380             SetSymbolValue(TLS_INDEX_LOCK,make_fixnum(0),0);
 381         }
 382 #define STATIC_TLS_INIT(sym,field) \
 383   ((struct symbol *)(sym-OTHER_POINTER_LOWTAG))->tls_index= \
 384   make_fixnum(THREAD_SLOT_OFFSET_WORDS(field))
 385
 386         STATIC_TLS_INIT(BINDING_STACK_START,binding_stack_start);
 387         STATIC_TLS_INIT(BINDING_STACK_POINTER,binding_stack_pointer);
 388         STATIC_TLS_INIT(CONTROL_STACK_START,control_stack_start);
 389         STATIC_TLS_INIT(CONTROL_STACK_END,control_stack_end);
 390         STATIC_TLS_INIT(ALIEN_STACK,alien_stack_pointer);
 391 #if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
 392         STATIC_TLS_INIT(PSEUDO_ATOMIC_BITS,pseudo_atomic_bits);
 393 #endif
 394 #undef STATIC_TLS_INIT
 395     }
 396 #endif
 397
 398     th=&per_thread->thread;
 399     th->os_address = spaces;
 400     th->control_stack_start = aligned_spaces;
 401     th->binding_stack_start=
 402         (lispobj*)((void*)th->control_stack_start+thread_control_stack_size);
 403     th->control_stack_end = th->binding_stack_start;
 404     th->alien_stack_start=
 405         (lispobj*)((void*)th->binding_stack_start+BINDING_STACK_SIZE);
 406     th->binding_stack_pointer=th->binding_stack_start;
 407     th->this=th;
 408     th->os_thread=0;
 409 #ifdef LISP_FEATURE_SB_THREAD
 410     th->os_attr=malloc(sizeof(pthread_attr_t));
 411     th->state_lock=(pthread_mutex_t *)((void *)th->alien_stack_start +
 412                                        ALIEN_STACK_SIZE);
 413     pthread_mutex_init(th->state_lock, NULL);
 414     th->state_cond=(pthread_cond_t *)((void *)th->state_lock +
 415                                       (sizeof(pthread_mutex_t)));
 416     pthread_cond_init(th->state_cond, NULL);
 417 #endif
 418     th->state=STATE_RUNNING;
 419 #ifdef LISP_FEATURE_STACK_GROWS_DOWNWARD_NOT_UPWARD
 420     th->alien_stack_pointer=((void *)th->alien_stack_start
 421                              + ALIEN_STACK_SIZE-N_WORD_BYTES);
 422 #else
 423     th->alien_stack_pointer=((void *)th->alien_stack_start);
 424 #endif
 425 #if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
 426     th->pseudo_atomic_bits=0;
 427 #endif
 428 #ifdef LISP_FEATURE_GENCGC
 429     gc_set_region_empty(&th->alloc_region);
 430 #endif
 431
 432 #ifndef LISP_FEATURE_SB_THREAD
 433     /* the tls-points-into-struct-thread trick is only good for threaded
 434      * sbcl, because unithread sbcl doesn't have tls.  So, we copy the
 435      * appropriate values from struct thread here, and make sure that
 436      * we use the appropriate SymbolValue macros to access any of the
 437      * variable quantities from the C runtime.  It's not quite OAOOM,
 438      * it just feels like it */
 439     SetSymbolValue(BINDING_STACK_START,(lispobj)th->binding_stack_start,th);
 440     SetSymbolValue(CONTROL_STACK_START,(lispobj)th->control_stack_start,th);
 441     SetSymbolValue(CONTROL_STACK_END,(lispobj)th->control_stack_end,th);
 442 #if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
 443     SetSymbolValue(BINDING_STACK_POINTER,(lispobj)th->binding_stack_pointer,th);
 444     SetSymbolValue(ALIEN_STACK,(lispobj)th->alien_stack_pointer,th);
 445     SetSymbolValue(PSEUDO_ATOMIC_BITS,(lispobj)th->pseudo_atomic_bits,th);
 446 #else
 447     current_binding_stack_pointer=th->binding_stack_pointer;
 448     current_control_stack_pointer=th->control_stack_start;
 449 #endif
 450 #endif
 451     bind_variable(CURRENT_CATCH_BLOCK,make_fixnum(0),th);
 452     bind_variable(CURRENT_UNWIND_PROTECT_BLOCK,make_fixnum(0),th);
 453     bind_variable(FREE_INTERRUPT_CONTEXT_INDEX,make_fixnum(0),th);
 454     bind_variable(INTERRUPT_PENDING, NIL,th);
 455     bind_variable(INTERRUPTS_ENABLED,T,th);
 456     bind_variable(ALLOW_WITH_INTERRUPTS,T,th);
 457     bind_variable(GC_PENDING,NIL,th);
 458     bind_variable(ALLOC_SIGNAL,NIL,th);
 459 #ifdef LISP_FEATURE_SB_THREAD
 460     bind_variable(STOP_FOR_GC_PENDING,NIL,th);
 461 #endif
 462
 463     th->interrupt_data = (struct interrupt_data *)
 464         os_validate(0,(sizeof (struct interrupt_data)));
 465     if (!th->interrupt_data) {
 466         free_thread_struct(th);
 467         return 0;
 468     }
 469     th->interrupt_data->pending_handler = 0;
 470     th->no_tls_value_marker=initial_function;
 471
 472     th->stepping = NIL;
 473     return th;
 474 }
 475
 476 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
 477 mach_port_t setup_mach_exception_handling_thread();
 478 kern_return_t mach_thread_init(mach_port_t thread_exception_port);
 479
 480 #endif
 481
 482 void create_initial_thread(lispobj initial_function) {
 483     struct thread *th=create_thread_struct(initial_function);
 484     if(th) {
 485 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
 486         setup_mach_exception_handling_thread();
 487 #endif
 488         initial_thread_trampoline(th); /* no return */
 489     } else lose("can't create initial thread\n");
 490 }
 491
 492 #ifdef LISP_FEATURE_SB_THREAD
 493
 494 #ifndef __USE_XOPEN2K
 495 extern int pthread_attr_setstack (pthread_attr_t *__attr, void *__stackaddr,
 496                                   size_t __stacksize);
 497 #endif
 498
 499 boolean create_os_thread(struct thread *th,os_thread_t *kid_tid)
 500 {
 501     /* The new thread inherits the restrictive signal mask set here,
 502      * and enables signals again when it is set up properly. */
 503     sigset_t newset,oldset;
 504     boolean r=1;
 505     int retcode = 0, initcode;
 506
 507     FSHOW_SIGNAL((stderr,"/create_os_thread: creating new thread\n"));
 508
 509 #ifdef LOCK_CREATE_THREAD
 510     retcode = pthread_mutex_lock(&create_thread_lock);
 511     gc_assert(retcode == 0);
 512     FSHOW_SIGNAL((stderr,"/create_os_thread: got lock\n"));
 513 #endif
 514     sigemptyset(&newset);
 515     /* Blocking deferrable signals is enough, no need to block
 516      * SIG_STOP_FOR_GC because the child process is not linked onto
 517      * all_threads until it's ready. */
 518     sigaddset_deferrable(&newset);
 519     thread_sigmask(SIG_BLOCK, &newset, &oldset);
 520
 521     if((initcode = pthread_attr_init(th->os_attr)) ||
 522        /* call_into_lisp_first_time switches the stack for the initial thread. For the
 523         * others, we use this. */
 524        (pthread_attr_setstack(th->os_attr,th->control_stack_start,thread_control_stack_size)) ||
 525        (retcode = pthread_create
 526         (kid_tid,th->os_attr,(void *(*)(void *))new_thread_trampoline,th))) {
 527         FSHOW_SIGNAL((stderr, "init = %d\n", initcode));
 528         FSHOW_SIGNAL((stderr, printf("pthread_create returned %d, errno %d\n", retcode, errno)));
 529         if(retcode < 0) {
 530             perror("create_os_thread");
 531         }
 532         r=0;
 533     }
 534
 535     thread_sigmask(SIG_SETMASK,&oldset,0);
 536 #ifdef LOCK_CREATE_THREAD
 537     retcode = pthread_mutex_unlock(&create_thread_lock);
 538     gc_assert(retcode == 0);
 539     FSHOW_SIGNAL((stderr,"/create_os_thread: released lock\n"));
 540 #endif
 541     return r;
 542 }
 543
 544 os_thread_t create_thread(lispobj initial_function) {
 545     struct thread *th;
 546     os_thread_t kid_tid;
 547
 548     /* Assuming that a fresh thread struct has no lisp objects in it,
 549      * linking it to all_threads can be left to the thread itself
 550      * without fear of gc lossage. initial_function violates this
 551      * assumption and must stay pinned until the child starts up. */
 552     th = create_thread_struct(initial_function);
 553     if(th==0) return 0;
 554
 555     if (create_os_thread(th,&kid_tid)) {
 556         return kid_tid;
 557     } else {
 558         free_thread_struct(th);
 559         return 0;
 560     }
 561 }
 562
 563 /* Send the signo to os_thread, retry if the rt signal queue is
 564  * full. */
 565 int
 566 kill_thread_safely(os_thread_t os_thread, int signo)
 567 {
 568     int r;
 569     /* The man page does not mention EAGAIN as a valid return value
 570      * for either pthread_kill or kill. But that's theory, this is
 571      * practice. By waiting here we assume that the delivery of this
 572      * signal is not necessary for the delivery of the signals in the
 573      * queue. In other words, we _assume_ there are no deadlocks. */
 574     while ((r=pthread_kill(os_thread,signo))==EAGAIN) {
 575         /* wait a bit then try again in the hope of the rt signal
 576          * queue not being full */
 577         FSHOW_SIGNAL((stderr,"/rt signal queue full\n"));
 578         /* FIXME: some kind of backoff (random, exponential) would be
 579          * nice. */
 580         sleep(1);
 581     }
 582     return r;
 583 }
 584
 585 int signal_interrupt_thread(os_thread_t os_thread)
 586 {
 587     int status = kill_thread_safely(os_thread, SIG_INTERRUPT_THREAD);
 588     FSHOW_SIGNAL((stderr,"/signal_interrupt_thread: %lu\n", os_thread));
 589     if (status == 0) {
 590         return 0;
 591     } else if (status == ESRCH) {
 592         return -1;
 593     } else {
 594         lose("cannot send SIG_INTERRUPT_THREAD to thread=%lu: %d, %s\n",
 595              os_thread, status, strerror(status));
 596     }
 597 }
 598
 599 /* stopping the world is a two-stage process.  From this thread we signal
 600  * all the others with SIG_STOP_FOR_GC.  The handler for this signal does
 601  * the usual pseudo-atomic checks (we don't want to stop a thread while
 602  * it's in the middle of allocation) then waits for another SIG_STOP_FOR_GC.
 603  */
 604
 605 /* To avoid deadlocks when gc stops the world all clients of each
 606  * mutex must enable or disable SIG_STOP_FOR_GC for the duration of
 607  * holding the lock, but they must agree on which. */
 608 void gc_stop_the_world()
 609 {
 610     struct thread *p,*th=arch_os_get_current_thread();
 611     int status, lock_ret;
 612 #ifdef LOCK_CREATE_THREAD
 613     /* KLUDGE: Stopping the thread during pthread_create() causes deadlock
 614      * on FreeBSD. */
 615     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:waiting on create_thread_lock\n"));
 616     lock_ret = pthread_mutex_lock(&create_thread_lock);
 617     gc_assert(lock_ret == 0);
 618     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:got create_thread_lock\n"));
 619 #endif
 620     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:waiting on lock\n"));
 621     /* keep threads from starting while the world is stopped. */
 622     lock_ret = pthread_mutex_lock(&all_threads_lock);      \
 623     gc_assert(lock_ret == 0);
 624
 625     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:got lock\n"));
 626     /* stop all other threads by sending them SIG_STOP_FOR_GC */
 627     for(p=all_threads; p; p=p->next) {
 628         gc_assert(p->os_thread != 0);
 629         FSHOW_SIGNAL((stderr,"/gc_stop_the_world: thread=%lu, state=%x\n",
 630                       p->os_thread, thread_state(p)));
 631         if((p!=th) && ((thread_state(p)==STATE_RUNNING))) {
 632             FSHOW_SIGNAL((stderr,"/gc_stop_the_world: suspending thread %lu\n",
 633                           p->os_thread));
 634             status=pthread_kill(p->os_thread,SIG_STOP_FOR_GC);
 635             if (status==ESRCH) {
 636                 /* This thread has exited. */
 637                 gc_assert(thread_state(p)==STATE_DEAD);
 638             } else if (status) {
 639                 lose("cannot send suspend thread=%lu: %d, %s\n",
 640                      p->os_thread,status,strerror(status));
 641             }
 642         }
 643     }
 644     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:signals sent\n"));
 645     for(p=all_threads;p;p=p->next) {
 646         if (p!=th) {
 647             FSHOW_SIGNAL
 648                 ((stderr,
 649                   "/gc_stop_the_world: waiting for thread=%lu: state=%x\n",
 650                   p->os_thread, thread_state(p)));
 651             wait_for_thread_state_change(p, STATE_RUNNING);
 652             if (p->state == STATE_RUNNING)
 653                 lose("/gc_stop_the_world: unexpected state");
 654         }
 655     }
 656     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:end\n"));
 657 }
 658
 659 void gc_start_the_world()
 660 {
 661     struct thread *p,*th=arch_os_get_current_thread();
 662     int lock_ret;
 663     /* if a resumed thread creates a new thread before we're done with
 664      * this loop, the new thread will get consed on the front of
 665      * all_threads, but it won't have been stopped so won't need
 666      * restarting */
 667     FSHOW_SIGNAL((stderr,"/gc_start_the_world:begin\n"));
 668     for(p=all_threads;p;p=p->next) {
 669         gc_assert(p->os_thread!=0);
 670         if (p!=th) {
 671             lispobj state = thread_state(p);
 672             if (state != STATE_DEAD) {
 673                 if(state != STATE_SUSPENDED) {
 674                     lose("gc_start_the_world: wrong thread state is %d\n",
 675                          fixnum_value(state));
 676                 }
 677                 FSHOW_SIGNAL((stderr, "/gc_start_the_world: resuming %lu\n",
 678                               p->os_thread));
 679                 set_thread_state(p, STATE_RUNNING);
 680             }
 681         }
 682     }
 683
 684     lock_ret = pthread_mutex_unlock(&all_threads_lock);
 685     gc_assert(lock_ret == 0);
 686 #ifdef LOCK_CREATE_THREAD
 687     lock_ret = pthread_mutex_unlock(&create_thread_lock);
 688     gc_assert(lock_ret == 0);
 689 #endif
 690
 691     FSHOW_SIGNAL((stderr,"/gc_start_the_world:end\n"));
 692 }
 693 #endif
 694
 695 int
 696 thread_yield()
 697 {
 698 #ifdef LISP_FEATURE_SB_THREAD
 699     return sched_yield();
 700 #else
 701     return 0;
 702 #endif
 703 }