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 CONTROL_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 QUEUE_FREEABLE_THREAD_STACKS
  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 struct freeable_stack {
  69 #ifdef QUEUE_FREEABLE_THREAD_STACKS
  70     struct freeable_stack *next;
  71 #endif
  72     os_thread_t os_thread;
  73     os_vm_address_t stack;
  74 };
  75
  76
  77 #ifdef QUEUE_FREEABLE_THREAD_STACKS
  78 static struct freeable_stack * volatile freeable_stack_queue = 0;
  79 static int freeable_stack_count = 0;
  80 pthread_mutex_t freeable_stack_lock = PTHREAD_MUTEX_INITIALIZER;
  81 #else
  82 static struct freeable_stack * volatile freeable_stack = 0;
  83 #endif
  84
  85 int dynamic_values_bytes=4096*sizeof(lispobj);  /* same for all threads */
  86 struct thread * volatile 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 #endif
  95
  96 #if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
  97 extern lispobj call_into_lisp_first_time(lispobj fun, lispobj *args, int nargs);
  98 #endif
  99
 100 static void
 101 link_thread(struct thread *th)
 102 {
 103     if (all_threads) all_threads->prev=th;
 104     th->next=all_threads;
 105     th->prev=0;
 106     all_threads=th;
 107 }
 108
 109 #ifdef LISP_FEATURE_SB_THREAD
 110 static void
 111 unlink_thread(struct thread *th)
 112 {
 113     if (th->prev)
 114         th->prev->next = th->next;
 115     else
 116         all_threads = th->next;
 117     if (th->next)
 118         th->next->prev = th->prev;
 119 }
 120 #endif
 121
 122 static int
 123 initial_thread_trampoline(struct thread *th)
 124 {
 125     lispobj function;
 126 #if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
 127     lispobj *args = NULL;
 128 #endif
 129     function = th->no_tls_value_marker;
 130     th->no_tls_value_marker = NO_TLS_VALUE_MARKER_WIDETAG;
 131     if(arch_os_thread_init(th)==0) return 1;
 132     link_thread(th);
 133     th->os_thread=thread_self();
 134 #ifndef LISP_FEATURE_WIN32
 135     protect_control_stack_guard_page(1);
 136 #endif
 137
 138 #if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
 139     return call_into_lisp_first_time(function,args,0);
 140 #else
 141     return funcall0(function);
 142 #endif
 143 }
 144
 145 #define THREAD_STRUCT_SIZE (THREAD_CONTROL_STACK_SIZE + BINDING_STACK_SIZE + \
 146                             ALIEN_STACK_SIZE + dynamic_values_bytes + \
 147                             32 * SIGSTKSZ)
 148
 149 #ifdef LISP_FEATURE_SB_THREAD
 150
 151 #ifdef QUEUE_FREEABLE_THREAD_STACKS
 152
 153 static void
 154 queue_freeable_thread_stack(struct thread *thread_to_be_cleaned_up)
 155 {
 156      if (thread_to_be_cleaned_up) {
 157         pthread_mutex_lock(&freeable_stack_lock);
 158         if (freeable_stack_queue) {
 159             struct freeable_stack *new_freeable_stack = 0, *next;
 160             next = freeable_stack_queue;
 161             while (next->next) {
 162                 next = next->next;
 163             }
 164             new_freeable_stack = (struct freeable_stack *)
 165                 os_validate(0, sizeof(struct freeable_stack));
 166             new_freeable_stack->next = NULL;
 167             new_freeable_stack->os_thread = thread_to_be_cleaned_up->os_thread;
 168             new_freeable_stack->stack = (os_vm_address_t)
 169                 thread_to_be_cleaned_up->control_stack_start;
 170             next->next = new_freeable_stack;
 171             freeable_stack_count++;
 172         } else {
 173             struct freeable_stack *new_freeable_stack = 0;
 174             new_freeable_stack = (struct freeable_stack *)
 175                 os_validate(0, sizeof(struct freeable_stack));
 176             new_freeable_stack->next = NULL;
 177             new_freeable_stack->os_thread = thread_to_be_cleaned_up->os_thread;
 178             new_freeable_stack->stack = (os_vm_address_t)
 179                 thread_to_be_cleaned_up->control_stack_start;
 180             freeable_stack_queue = new_freeable_stack;
 181             freeable_stack_count++;
 182         }
 183         pthread_mutex_unlock(&freeable_stack_lock);
 184     }
 185 }
 186
 187 #define FREEABLE_STACK_QUEUE_SIZE 4
 188
 189 static void
 190 free_freeable_stacks() {
 191     if (freeable_stack_queue && (freeable_stack_count > FREEABLE_STACK_QUEUE_SIZE)) {
 192         struct freeable_stack* old;
 193         pthread_mutex_lock(&freeable_stack_lock);
 194         old = freeable_stack_queue;
 195         freeable_stack_queue = old->next;
 196         freeable_stack_count--;
 197         gc_assert(pthread_join(old->os_thread, NULL) == 0);
 198         FSHOW((stderr, "freeing thread %x stack\n", old->os_thread));
 199         os_invalidate(old->stack, THREAD_STRUCT_SIZE);
 200         os_invalidate((os_vm_address_t)old, sizeof(struct freeable_stack));
 201         pthread_mutex_unlock(&freeable_stack_lock);
 202     }
 203 }
 204
 205 #elif defined(CREATE_CLEANUP_THREAD)
 206 static void *
 207 cleanup_thread(void *arg)
 208 {
 209     struct freeable_stack *freeable = arg;
 210     pthread_t self = pthread_self();
 211
 212     FSHOW((stderr, "/cleaner thread(%p): joining %p\n",
 213            self, freeable->os_thread));
 214     gc_assert(pthread_join(freeable->os_thread, NULL) == 0);
 215     FSHOW((stderr, "/cleaner thread(%p): free stack %p\n",
 216            self, freeable->stack));
 217     os_invalidate(freeable->stack, THREAD_STRUCT_SIZE);
 218     free(freeable);
 219
 220     pthread_detach(self);
 221
 222     return NULL;
 223 }
 224
 225 static void
 226 create_cleanup_thread(struct thread *thread_to_be_cleaned_up)
 227 {
 228     pthread_t thread;
 229     int result;
 230
 231     if (thread_to_be_cleaned_up) {
 232         struct freeable_stack *freeable =
 233             malloc(sizeof(struct freeable_stack));
 234         gc_assert(freeable != NULL);
 235         freeable->os_thread = thread_to_be_cleaned_up->os_thread;
 236         freeable->stack =
 237             (os_vm_address_t) thread_to_be_cleaned_up->control_stack_start;
 238         result = pthread_create(&thread, NULL, cleanup_thread, freeable);
 239         gc_assert(result == 0);
 240         sched_yield();
 241     }
 242 }
 243
 244 #else
 245 static void
 246 free_thread_stack_later(struct thread *thread_to_be_cleaned_up)
 247 {
 248     struct freeable_stack *new_freeable_stack = 0;
 249     if (thread_to_be_cleaned_up) {
 250         new_freeable_stack = (struct freeable_stack *)
 251             os_validate(0, sizeof(struct freeable_stack));
 252         new_freeable_stack->os_thread = thread_to_be_cleaned_up->os_thread;
 253         new_freeable_stack->stack = (os_vm_address_t)
 254             thread_to_be_cleaned_up->control_stack_start;
 255     }
 256     new_freeable_stack = (struct freeable_stack *)
 257         swap_lispobjs((lispobj *)(void *)&freeable_stack,
 258                       (lispobj)new_freeable_stack);
 259     if (new_freeable_stack) {
 260         FSHOW((stderr,"/reaping %p\n", (void*) new_freeable_stack->os_thread));
 261         /* Under NPTL pthread_join really waits until the thread
 262          * exists and the stack can be safely freed. This is sadly not
 263          * mandated by the pthread spec. */
 264         gc_assert(pthread_join(new_freeable_stack->os_thread, NULL) == 0);
 265         os_invalidate(new_freeable_stack->stack, THREAD_STRUCT_SIZE);
 266         os_invalidate((os_vm_address_t) new_freeable_stack,
 267                       sizeof(struct freeable_stack));
 268     }
 269 }
 270 #endif
 271
 272 /* this is the first thing that runs in the child (which is why the
 273  * silly calling convention).  Basically it calls the user's requested
 274  * lisp function after doing arch_os_thread_init and whatever other
 275  * bookkeeping needs to be done
 276  */
 277 int
 278 new_thread_trampoline(struct thread *th)
 279 {
 280     lispobj function;
 281     int result, lock_ret;
 282
 283     FSHOW((stderr,"/creating thread %lu\n", thread_self()));
 284     function = th->no_tls_value_marker;
 285     th->no_tls_value_marker = NO_TLS_VALUE_MARKER_WIDETAG;
 286     if(arch_os_thread_init(th)==0) {
 287         /* FIXME: handle error */
 288         lose("arch_os_thread_init failed\n");
 289     }
 290
 291     th->os_thread=thread_self();
 292     protect_control_stack_guard_page(1);
 293     /* Since GC can only know about this thread from the all_threads
 294      * list and we're just adding this thread to it there is no danger
 295      * of deadlocking even with SIG_STOP_FOR_GC blocked (which it is
 296      * not). */
 297     lock_ret = pthread_mutex_lock(&all_threads_lock);
 298     gc_assert(lock_ret == 0);
 299     link_thread(th);
 300     lock_ret = pthread_mutex_unlock(&all_threads_lock);
 301     gc_assert(lock_ret == 0);
 302
 303     result = funcall0(function);
 304
 305     /* Block GC */
 306     block_blockable_signals();
 307     th->state=STATE_DEAD;
 308
 309     /* SIG_STOP_FOR_GC is blocked and GC might be waiting for this
 310      * thread, but since we are already dead it won't wait long. */
 311     lock_ret = pthread_mutex_lock(&all_threads_lock);
 312     gc_assert(lock_ret == 0);
 313
 314     gc_alloc_update_page_tables(0, &th->alloc_region);
 315     unlink_thread(th);
 316     pthread_mutex_unlock(&all_threads_lock);
 317     gc_assert(lock_ret == 0);
 318
 319     if(th->tls_cookie>=0) arch_os_thread_cleanup(th);
 320     os_invalidate((os_vm_address_t)th->interrupt_data,
 321                   (sizeof (struct interrupt_data)));
 322
 323 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
 324     FSHOW((stderr, "Deallocating mach port %x\n", THREAD_STRUCT_TO_EXCEPTION_PORT(th)));
 325     mach_port_move_member(mach_task_self(),
 326                           THREAD_STRUCT_TO_EXCEPTION_PORT(th),
 327                           MACH_PORT_NULL);
 328     mach_port_deallocate(mach_task_self(),
 329                          THREAD_STRUCT_TO_EXCEPTION_PORT(th));
 330     mach_port_destroy(mach_task_self(),
 331                       THREAD_STRUCT_TO_EXCEPTION_PORT(th));
 332 #endif
 333
 334 #ifdef QUEUE_FREEABLE_THREAD_STACKS
 335     queue_freeable_thread_stack(th);
 336 #elif defined(CREATE_CLEANUP_THREAD)
 337     create_cleanup_thread(th);
 338 #else
 339     free_thread_stack_later(th);
 340 #endif
 341
 342     FSHOW((stderr,"/exiting thread %p\n", thread_self()));
 343     return result;
 344 }
 345
 346 #endif /* LISP_FEATURE_SB_THREAD */
 347
 348 static void
 349 free_thread_struct(struct thread *th)
 350 {
 351     if (th->interrupt_data)
 352         os_invalidate((os_vm_address_t) th->interrupt_data,
 353                       (sizeof (struct interrupt_data)));
 354     os_invalidate((os_vm_address_t) th->control_stack_start,
 355                   THREAD_STRUCT_SIZE);
 356 }
 357
 358 /* this is called from any other thread to create the new one, and
 359  * initialize all parts of it that can be initialized from another
 360  * thread
 361  */
 362
 363 static struct thread *
 364 create_thread_struct(lispobj initial_function) {
 365     union per_thread_data *per_thread;
 366     struct thread *th=0;        /*  subdue gcc */
 367     void *spaces=0;
 368 #ifdef LISP_FEATURE_SB_THREAD
 369     int i;
 370 #endif
 371
 372 #ifdef CREATE_CLEANUP_THREAD
 373     /* Give a chance for cleanup threads to run. */
 374     sched_yield();
 375 #endif
 376     /* may as well allocate all the spaces at once: it saves us from
 377      * having to decide what to do if only some of the allocations
 378      * succeed */
 379     spaces=os_validate(0, THREAD_STRUCT_SIZE);
 380     if(!spaces)
 381          return NULL;
 382     per_thread=(union per_thread_data *)
 383         (spaces+
 384          THREAD_CONTROL_STACK_SIZE+
 385          BINDING_STACK_SIZE+
 386          ALIEN_STACK_SIZE);
 387
 388 #ifdef LISP_FEATURE_SB_THREAD
 389     for(i = 0; i < (dynamic_values_bytes / sizeof(lispobj)); i++)
 390         per_thread->dynamic_values[i] = NO_TLS_VALUE_MARKER_WIDETAG;
 391     if (all_threads == 0) {
 392         if(SymbolValue(FREE_TLS_INDEX,0)==UNBOUND_MARKER_WIDETAG) {
 393             SetSymbolValue
 394                 (FREE_TLS_INDEX,
 395                  /* FIXME: should be MAX_INTERRUPTS -1 ? */
 396                  make_fixnum(MAX_INTERRUPTS+
 397                              sizeof(struct thread)/sizeof(lispobj)),
 398                  0);
 399             SetSymbolValue(TLS_INDEX_LOCK,make_fixnum(0),0);
 400         }
 401 #define STATIC_TLS_INIT(sym,field) \
 402   ((struct symbol *)(sym-OTHER_POINTER_LOWTAG))->tls_index= \
 403   make_fixnum(THREAD_SLOT_OFFSET_WORDS(field))
 404
 405         STATIC_TLS_INIT(BINDING_STACK_START,binding_stack_start);
 406         STATIC_TLS_INIT(BINDING_STACK_POINTER,binding_stack_pointer);
 407         STATIC_TLS_INIT(CONTROL_STACK_START,control_stack_start);
 408         STATIC_TLS_INIT(CONTROL_STACK_END,control_stack_end);
 409         STATIC_TLS_INIT(ALIEN_STACK,alien_stack_pointer);
 410 #if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
 411         STATIC_TLS_INIT(PSEUDO_ATOMIC_BITS,pseudo_atomic_bits);
 412 #endif
 413 #undef STATIC_TLS_INIT
 414     }
 415 #endif
 416
 417     th=&per_thread->thread;
 418     th->control_stack_start = spaces;
 419     th->binding_stack_start=
 420         (lispobj*)((void*)th->control_stack_start+THREAD_CONTROL_STACK_SIZE);
 421     th->control_stack_end = th->binding_stack_start;
 422     th->alien_stack_start=
 423         (lispobj*)((void*)th->binding_stack_start+BINDING_STACK_SIZE);
 424     th->binding_stack_pointer=th->binding_stack_start;
 425     th->this=th;
 426     th->os_thread=0;
 427     th->state=STATE_RUNNING;
 428 #ifdef LISP_FEATURE_STACK_GROWS_DOWNWARD_NOT_UPWARD
 429     th->alien_stack_pointer=((void *)th->alien_stack_start
 430                              + ALIEN_STACK_SIZE-N_WORD_BYTES);
 431 #else
 432     th->alien_stack_pointer=((void *)th->alien_stack_start);
 433 #endif
 434 #if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
 435     th->pseudo_atomic_bits=0;
 436 #endif
 437 #ifdef LISP_FEATURE_GENCGC
 438     gc_set_region_empty(&th->alloc_region);
 439 #endif
 440
 441 #ifndef LISP_FEATURE_SB_THREAD
 442     /* the tls-points-into-struct-thread trick is only good for threaded
 443      * sbcl, because unithread sbcl doesn't have tls.  So, we copy the
 444      * appropriate values from struct thread here, and make sure that
 445      * we use the appropriate SymbolValue macros to access any of the
 446      * variable quantities from the C runtime.  It's not quite OAOOM,
 447      * it just feels like it */
 448     SetSymbolValue(BINDING_STACK_START,(lispobj)th->binding_stack_start,th);
 449     SetSymbolValue(CONTROL_STACK_START,(lispobj)th->control_stack_start,th);
 450     SetSymbolValue(CONTROL_STACK_END,(lispobj)th->control_stack_end,th);
 451 #if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
 452     SetSymbolValue(BINDING_STACK_POINTER,(lispobj)th->binding_stack_pointer,th);
 453     SetSymbolValue(ALIEN_STACK,(lispobj)th->alien_stack_pointer,th);
 454     SetSymbolValue(PSEUDO_ATOMIC_BITS,(lispobj)th->pseudo_atomic_bits,th);
 455 #else
 456     current_binding_stack_pointer=th->binding_stack_pointer;
 457     current_control_stack_pointer=th->control_stack_start;
 458 #endif
 459 #endif
 460     bind_variable(CURRENT_CATCH_BLOCK,make_fixnum(0),th);
 461     bind_variable(CURRENT_UNWIND_PROTECT_BLOCK,make_fixnum(0),th);
 462     bind_variable(FREE_INTERRUPT_CONTEXT_INDEX,make_fixnum(0),th);
 463     bind_variable(INTERRUPT_PENDING, NIL,th);
 464     bind_variable(INTERRUPTS_ENABLED,T,th);
 465     bind_variable(ALLOW_WITH_INTERRUPTS,T,th);
 466     bind_variable(GC_PENDING,NIL,th);
 467 #ifdef LISP_FEATURE_SB_THREAD
 468     bind_variable(STOP_FOR_GC_PENDING,NIL,th);
 469 #endif
 470
 471     th->interrupt_data = (struct interrupt_data *)
 472         os_validate(0,(sizeof (struct interrupt_data)));
 473     if (!th->interrupt_data) {
 474         free_thread_struct(th);
 475         return 0;
 476     }
 477     th->interrupt_data->pending_handler = 0;
 478     th->no_tls_value_marker=initial_function;
 479
 480     th->stepping = NIL;
 481     return th;
 482 }
 483
 484 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
 485 mach_port_t setup_mach_exception_handling_thread();
 486 kern_return_t mach_thread_init(mach_port_t thread_exception_port);
 487
 488 #endif
 489
 490 void create_initial_thread(lispobj initial_function) {
 491     struct thread *th=create_thread_struct(initial_function);
 492     if(th) {
 493 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
 494         kern_return_t ret;
 495
 496         setup_mach_exception_handling_thread();
 497 #endif
 498         initial_thread_trampoline(th); /* no return */
 499     } else lose("can't create initial thread\n");
 500 }
 501
 502 #ifdef LISP_FEATURE_SB_THREAD
 503
 504 #ifndef __USE_XOPEN2K
 505 extern int pthread_attr_setstack (pthread_attr_t *__attr, void *__stackaddr,
 506                                   size_t __stacksize);
 507 #endif
 508
 509 boolean create_os_thread(struct thread *th,os_thread_t *kid_tid)
 510 {
 511     /* The new thread inherits the restrictive signal mask set here,
 512      * and enables signals again when it is set up properly. */
 513     pthread_attr_t attr;
 514     sigset_t newset,oldset;
 515     boolean r=1;
 516     int retcode, initcode, sizecode, addrcode;
 517
 518     FSHOW_SIGNAL((stderr,"/create_os_thread: creating new thread\n"));
 519
 520 #ifdef LOCK_CREATE_THREAD
 521     retcode = pthread_mutex_lock(&create_thread_lock);
 522     gc_assert(retcode == 0);
 523     FSHOW_SIGNAL((stderr,"/create_os_thread: got lock\n"));
 524 #endif
 525     sigemptyset(&newset);
 526     /* Blocking deferrable signals is enough, no need to block
 527      * SIG_STOP_FOR_GC because the child process is not linked onto
 528      * all_threads until it's ready. */
 529     sigaddset_deferrable(&newset);
 530     thread_sigmask(SIG_BLOCK, &newset, &oldset);
 531
 532 #if defined(LISP_FEATURE_DARWIN)
 533 #define CONTROL_STACK_ADJUST 8192 /* darwin wants page-aligned stacks */
 534 #else
 535 #define CONTROL_STACK_ADJUST 16
 536 #endif
 537
 538     if((initcode = pthread_attr_init(&attr)) ||
 539        /* FIXME: why do we even have this in the first place? */
 540        (pthread_attr_setstack(&attr,th->control_stack_start,
 541                               THREAD_CONTROL_STACK_SIZE-CONTROL_STACK_ADJUST)) ||
 542 #undef CONTROL_STACK_ADJUST
 543        (retcode = pthread_create
 544         (kid_tid,&attr,(void *(*)(void *))new_thread_trampoline,th))) {
 545         FSHOW_SIGNAL((stderr, "init, size, addr = %d, %d, %d\n", initcode, sizecode, addrcode));
 546         FSHOW_SIGNAL((stderr, printf("pthread_create returned %d, errno %d\n", retcode, errno)));
 547         FSHOW_SIGNAL((stderr, "wanted stack size %d, min stack size %d\n",
 548                       THREAD_CONTROL_STACK_SIZE-16, PTHREAD_STACK_MIN));
 549         if(retcode < 0) {
 550             perror("create_os_thread");
 551         }
 552         r=0;
 553     }
 554
 555 #ifdef QUEUE_FREEABLE_THREAD_STACKS
 556     free_freeable_stacks();
 557 #endif
 558     thread_sigmask(SIG_SETMASK,&oldset,0);
 559 #ifdef LOCK_CREATE_THREAD
 560     retcode = pthread_mutex_unlock(&create_thread_lock);
 561     gc_assert(retcode == 0);
 562     FSHOW_SIGNAL((stderr,"/create_os_thread: released lock\n"));
 563 #endif
 564     return r;
 565 }
 566
 567 os_thread_t create_thread(lispobj initial_function) {
 568     struct thread *th;
 569     os_thread_t kid_tid;
 570
 571     /* Assuming that a fresh thread struct has no lisp objects in it,
 572      * linking it to all_threads can be left to the thread itself
 573      * without fear of gc lossage. initial_function violates this
 574      * assumption and must stay pinned until the child starts up. */
 575     th = create_thread_struct(initial_function);
 576     if(th==0) return 0;
 577
 578     if (create_os_thread(th,&kid_tid)) {
 579         return kid_tid;
 580     } else {
 581         free_thread_struct(th);
 582         return 0;
 583     }
 584 }
 585
 586 /* Send the signo to os_thread, retry if the rt signal queue is
 587  * full. */
 588 int
 589 kill_thread_safely(os_thread_t os_thread, int signo)
 590 {
 591     int r;
 592     /* The man page does not mention EAGAIN as a valid return value
 593      * for either pthread_kill or kill. But that's theory, this is
 594      * practice. By waiting here we assume that the delivery of this
 595      * signal is not necessary for the delivery of the signals in the
 596      * queue. In other words, we _assume_ there are no deadlocks. */
 597     while ((r=pthread_kill(os_thread,signo))==EAGAIN) {
 598         /* wait a bit then try again in the hope of the rt signal
 599          * queue not being full */
 600         FSHOW_SIGNAL((stderr,"/rt signal queue full\n"));
 601         /* FIXME: some kind of backoff (random, exponential) would be
 602          * nice. */
 603         sleep(1);
 604     }
 605     return r;
 606 }
 607
 608 int signal_interrupt_thread(os_thread_t os_thread)
 609 {
 610     int status = kill_thread_safely(os_thread, SIG_INTERRUPT_THREAD);
 611     if (status == 0) {
 612         return 0;
 613     } else if (status == ESRCH) {
 614         return -1;
 615     } else {
 616         lose("cannot send SIG_INTERRUPT_THREAD to thread=%lu: %d, %s\n",
 617              os_thread, status, strerror(status));
 618     }
 619 }
 620
 621 /* stopping the world is a two-stage process.  From this thread we signal
 622  * all the others with SIG_STOP_FOR_GC.  The handler for this signal does
 623  * the usual pseudo-atomic checks (we don't want to stop a thread while
 624  * it's in the middle of allocation) then waits for another SIG_STOP_FOR_GC.
 625  */
 626
 627 /* To avoid deadlocks when gc stops the world all clients of each
 628  * mutex must enable or disable SIG_STOP_FOR_GC for the duration of
 629  * holding the lock, but they must agree on which. */
 630 void gc_stop_the_world()
 631 {
 632     struct thread *p,*th=arch_os_get_current_thread();
 633     int status, lock_ret;
 634 #ifdef LOCK_CREATE_THREAD
 635     /* KLUDGE: Stopping the thread during pthread_create() causes deadlock
 636      * on FreeBSD. */
 637     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:waiting on create_thread_lock, thread=%lu\n",
 638                   th->os_thread));
 639     lock_ret = pthread_mutex_lock(&create_thread_lock);
 640     gc_assert(lock_ret == 0);
 641     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:got create_thread_lock, thread=%lu\n",
 642                   th->os_thread));
 643 #endif
 644     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:waiting on lock, thread=%lu\n",
 645                   th->os_thread));
 646     /* keep threads from starting while the world is stopped. */
 647     lock_ret = pthread_mutex_lock(&all_threads_lock);      \
 648     gc_assert(lock_ret == 0);
 649
 650     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:got lock, thread=%lu\n",
 651                   th->os_thread));
 652     /* stop all other threads by sending them SIG_STOP_FOR_GC */
 653     for(p=all_threads; p; p=p->next) {
 654         gc_assert(p->os_thread != 0);
 655         FSHOW_SIGNAL((stderr,"/gc_stop_the_world: p->state: %x\n", p->state));
 656         if((p!=th) && ((p->state==STATE_RUNNING))) {
 657             FSHOW_SIGNAL((stderr,"/gc_stop_the_world: suspending %x, os_thread %x\n",
 658                           p, p->os_thread));
 659             status=kill_thread_safely(p->os_thread,SIG_STOP_FOR_GC);
 660             if (status==ESRCH) {
 661                 /* This thread has exited. */
 662                 gc_assert(p->state==STATE_DEAD);
 663             } else if (status) {
 664                 lose("cannot send suspend thread=%lu: %d, %s\n",
 665                      p->os_thread,status,strerror(status));
 666             }
 667         }
 668     }
 669     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:signals sent\n"));
 670     /* wait for the running threads to stop or finish */
 671     for(p=all_threads;p;) {
 672         FSHOW_SIGNAL((stderr,"/gc_stop_the_world: th: %p, p: %p\n", th, p));
 673         if((p!=th) && (p->state==STATE_RUNNING)) {
 674             sched_yield();
 675         } else {
 676             p=p->next;
 677         }
 678     }
 679     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:end\n"));
 680 }
 681
 682 void gc_start_the_world()
 683 {
 684     struct thread *p,*th=arch_os_get_current_thread();
 685     int status, lock_ret;
 686     /* if a resumed thread creates a new thread before we're done with
 687      * this loop, the new thread will get consed on the front of
 688      * all_threads, but it won't have been stopped so won't need
 689      * restarting */
 690     FSHOW_SIGNAL((stderr,"/gc_start_the_world:begin\n"));
 691     for(p=all_threads;p;p=p->next) {
 692         gc_assert(p->os_thread!=0);
 693         if((p!=th) && (p->state!=STATE_DEAD)) {
 694             if(p->state!=STATE_SUSPENDED) {
 695                 lose("gc_start_the_world: wrong thread state is %d\n",
 696                      fixnum_value(p->state));
 697             }
 698             FSHOW_SIGNAL((stderr, "/gc_start_the_world: resuming %lu\n",
 699                           p->os_thread));
 700             p->state=STATE_RUNNING;
 701
 702 #if defined(SIG_RESUME_FROM_GC)
 703             status=kill_thread_safely(p->os_thread,SIG_RESUME_FROM_GC);
 704 #else
 705             status=kill_thread_safely(p->os_thread,SIG_STOP_FOR_GC);
 706 #endif
 707             if (status) {
 708                 lose("cannot resume thread=%lu: %d, %s\n",
 709                      p->os_thread,status,strerror(status));
 710             }
 711         }
 712     }
 713     /* If we waited here until all threads leave STATE_SUSPENDED, then
 714      * SIG_STOP_FOR_GC wouldn't need to be a rt signal. That has some
 715      * performance implications, but does away with the 'rt signal
 716      * queue full' problem. */
 717
 718     lock_ret = pthread_mutex_unlock(&all_threads_lock);
 719     gc_assert(lock_ret == 0);
 720 #ifdef LOCK_CREATE_THREAD
 721     lock_ret = pthread_mutex_unlock(&create_thread_lock);
 722     gc_assert(lock_ret == 0);
 723 #endif
 724
 725     FSHOW_SIGNAL((stderr,"/gc_start_the_world:end\n"));
 726 }
 727 #endif