5a2fa87e797146cff13738bb7937e31f6b6e50e3
[sbcl.git] / 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     check_deferrables_blocked_or_lose();
262     check_gc_signals_unblocked_or_lose();
263     function = th->no_tls_value_marker;
264     th->no_tls_value_marker = NO_TLS_VALUE_MARKER_WIDETAG;
265     if(arch_os_thread_init(th)==0) {
266         /* FIXME: handle error */
267         lose("arch_os_thread_init failed\n");
268     }
269
270     th->os_thread=thread_self();
271     protect_control_stack_guard_page(1);
272     /* Since GC can only know about this thread from the all_threads
273      * list and we're just adding this thread to it, there is no
274      * danger of deadlocking even with SIG_STOP_FOR_GC blocked (which
275      * it is not). */
276     lock_ret = pthread_mutex_lock(&all_threads_lock);
277     gc_assert(lock_ret == 0);
278     link_thread(th);
279     lock_ret = pthread_mutex_unlock(&all_threads_lock);
280     gc_assert(lock_ret == 0);
281
282     result = funcall0(function);
283
284     /* Block GC */
285     block_blockable_signals();
286     set_thread_state(th, STATE_DEAD);
287
288     /* SIG_STOP_FOR_GC is blocked and GC might be waiting for this
289      * thread, but since we are already dead it won't wait long. */
290     lock_ret = pthread_mutex_lock(&all_threads_lock);
291     gc_assert(lock_ret == 0);
292
293     gc_alloc_update_page_tables(BOXED_PAGE_FLAG, &th->alloc_region);
294     unlink_thread(th);
295     pthread_mutex_unlock(&all_threads_lock);
296     gc_assert(lock_ret == 0);
297
298     if(th->tls_cookie>=0) arch_os_thread_cleanup(th);
299     pthread_mutex_destroy(th->state_lock);
300     pthread_cond_destroy(th->state_cond);
301
302     os_invalidate((os_vm_address_t)th->interrupt_data,
303                   (sizeof (struct interrupt_data)));
304
305 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
306     FSHOW((stderr, "Deallocating mach port %x\n", THREAD_STRUCT_TO_EXCEPTION_PORT(th)));
307     mach_port_move_member(mach_task_self(),
308                           THREAD_STRUCT_TO_EXCEPTION_PORT(th),
309                           MACH_PORT_NULL);
310     mach_port_deallocate(mach_task_self(),
311                          THREAD_STRUCT_TO_EXCEPTION_PORT(th));
312     mach_port_destroy(mach_task_self(),
313                       THREAD_STRUCT_TO_EXCEPTION_PORT(th));
314 #endif
315
316     schedule_thread_post_mortem(th);
317     FSHOW((stderr,"/exiting thread %lu\n", thread_self()));
318     return result;
319 }
320
321 #endif /* LISP_FEATURE_SB_THREAD */
322
323 static void
324 free_thread_struct(struct thread *th)
325 {
326     if (th->interrupt_data)
327         os_invalidate((os_vm_address_t) th->interrupt_data,
328                       (sizeof (struct interrupt_data)));
329     os_invalidate((os_vm_address_t) th->os_address,
330                   THREAD_STRUCT_SIZE);
331 }
332
333 /* this is called from any other thread to create the new one, and
334  * initialize all parts of it that can be initialized from another
335  * thread
336  */
337
338 static struct thread *
339 create_thread_struct(lispobj initial_function) {
340     union per_thread_data *per_thread;
341     struct thread *th=0;        /*  subdue gcc */
342     void *spaces=0;
343     void *aligned_spaces=0;
344 #ifdef LISP_FEATURE_SB_THREAD
345     unsigned int i;
346 #endif
347
348     /* May as well allocate all the spaces at once: it saves us from
349      * having to decide what to do if only some of the allocations
350      * succeed. SPACES must be appropriately aligned, since the GC
351      * expects the control stack to start at a page boundary -- and
352      * the OS may have even more rigorous requirements. We can't rely
353      * on the alignment passed from os_validate, since that might
354      * assume the current (e.g. 4k) pagesize, while we calculate with
355      * the biggest (e.g. 64k) pagesize allowed by the ABI. */
356     spaces=os_validate(0, THREAD_STRUCT_SIZE);
357     if(!spaces)
358         return NULL;
359     /* Aligning up is safe as THREAD_STRUCT_SIZE has
360      * THREAD_ALIGNMENT_BYTES padding. */
361     aligned_spaces = (void *)((((unsigned long)(char *)spaces)
362                                + THREAD_ALIGNMENT_BYTES-1)
363                               &~(unsigned long)(THREAD_ALIGNMENT_BYTES-1));
364     per_thread=(union per_thread_data *)
365         (aligned_spaces+
366          thread_control_stack_size+
367          BINDING_STACK_SIZE+
368          ALIEN_STACK_SIZE +
369          THREAD_STATE_LOCK_SIZE);
370
371 #ifdef LISP_FEATURE_SB_THREAD
372     for(i = 0; i < (dynamic_values_bytes / sizeof(lispobj)); i++)
373         per_thread->dynamic_values[i] = NO_TLS_VALUE_MARKER_WIDETAG;
374     if (all_threads == 0) {
375         if(SymbolValue(FREE_TLS_INDEX,0)==UNBOUND_MARKER_WIDETAG) {
376             SetSymbolValue
377                 (FREE_TLS_INDEX,
378                  /* FIXME: should be MAX_INTERRUPTS -1 ? */
379                  make_fixnum(MAX_INTERRUPTS+
380                              sizeof(struct thread)/sizeof(lispobj)),
381                  0);
382             SetSymbolValue(TLS_INDEX_LOCK,make_fixnum(0),0);
383         }
384 #define STATIC_TLS_INIT(sym,field) \
385   ((struct symbol *)(sym-OTHER_POINTER_LOWTAG))->tls_index= \
386   make_fixnum(THREAD_SLOT_OFFSET_WORDS(field))
387
388         STATIC_TLS_INIT(BINDING_STACK_START,binding_stack_start);
389         STATIC_TLS_INIT(BINDING_STACK_POINTER,binding_stack_pointer);
390         STATIC_TLS_INIT(CONTROL_STACK_START,control_stack_start);
391         STATIC_TLS_INIT(CONTROL_STACK_END,control_stack_end);
392         STATIC_TLS_INIT(ALIEN_STACK,alien_stack_pointer);
393 #if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
394         STATIC_TLS_INIT(PSEUDO_ATOMIC_BITS,pseudo_atomic_bits);
395 #endif
396 #undef STATIC_TLS_INIT
397     }
398 #endif
399
400     th=&per_thread->thread;
401     th->os_address = spaces;
402     th->control_stack_start = aligned_spaces;
403     th->binding_stack_start=
404         (lispobj*)((void*)th->control_stack_start+thread_control_stack_size);
405     th->control_stack_end = th->binding_stack_start;
406     th->alien_stack_start=
407         (lispobj*)((void*)th->binding_stack_start+BINDING_STACK_SIZE);
408     th->binding_stack_pointer=th->binding_stack_start;
409     th->this=th;
410     th->os_thread=0;
411 #ifdef LISP_FEATURE_SB_THREAD
412     th->os_attr=malloc(sizeof(pthread_attr_t));
413     th->state_lock=(pthread_mutex_t *)((void *)th->alien_stack_start +
414                                        ALIEN_STACK_SIZE);
415     pthread_mutex_init(th->state_lock, NULL);
416     th->state_cond=(pthread_cond_t *)((void *)th->state_lock +
417                                       (sizeof(pthread_mutex_t)));
418     pthread_cond_init(th->state_cond, NULL);
419 #endif
420     th->state=STATE_RUNNING;
421 #ifdef LISP_FEATURE_STACK_GROWS_DOWNWARD_NOT_UPWARD
422     th->alien_stack_pointer=((void *)th->alien_stack_start
423                              + ALIEN_STACK_SIZE-N_WORD_BYTES);
424 #else
425     th->alien_stack_pointer=((void *)th->alien_stack_start);
426 #endif
427 #if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
428     th->pseudo_atomic_bits=0;
429 #endif
430 #ifdef LISP_FEATURE_GENCGC
431     gc_set_region_empty(&th->alloc_region);
432 #endif
433
434 #ifndef LISP_FEATURE_SB_THREAD
435     /* the tls-points-into-struct-thread trick is only good for threaded
436      * sbcl, because unithread sbcl doesn't have tls.  So, we copy the
437      * appropriate values from struct thread here, and make sure that
438      * we use the appropriate SymbolValue macros to access any of the
439      * variable quantities from the C runtime.  It's not quite OAOOM,
440      * it just feels like it */
441     SetSymbolValue(BINDING_STACK_START,(lispobj)th->binding_stack_start,th);
442     SetSymbolValue(CONTROL_STACK_START,(lispobj)th->control_stack_start,th);
443     SetSymbolValue(CONTROL_STACK_END,(lispobj)th->control_stack_end,th);
444 #if defined(LISP_FEATURE_X86) || defined (LISP_FEATURE_X86_64)
445     SetSymbolValue(BINDING_STACK_POINTER,(lispobj)th->binding_stack_pointer,th);
446     SetSymbolValue(ALIEN_STACK,(lispobj)th->alien_stack_pointer,th);
447     SetSymbolValue(PSEUDO_ATOMIC_BITS,(lispobj)th->pseudo_atomic_bits,th);
448 #else
449     current_binding_stack_pointer=th->binding_stack_pointer;
450     current_control_stack_pointer=th->control_stack_start;
451 #endif
452 #endif
453     bind_variable(CURRENT_CATCH_BLOCK,make_fixnum(0),th);
454     bind_variable(CURRENT_UNWIND_PROTECT_BLOCK,make_fixnum(0),th);
455     bind_variable(FREE_INTERRUPT_CONTEXT_INDEX,make_fixnum(0),th);
456     bind_variable(INTERRUPT_PENDING, NIL,th);
457     bind_variable(INTERRUPTS_ENABLED,T,th);
458     bind_variable(ALLOW_WITH_INTERRUPTS,T,th);
459     bind_variable(GC_PENDING,NIL,th);
460     bind_variable(ALLOC_SIGNAL,NIL,th);
461 #ifdef LISP_FEATURE_SB_THREAD
462     bind_variable(STOP_FOR_GC_PENDING,NIL,th);
463 #endif
464
465     th->interrupt_data = (struct interrupt_data *)
466         os_validate(0,(sizeof (struct interrupt_data)));
467     if (!th->interrupt_data) {
468         free_thread_struct(th);
469         return 0;
470     }
471     th->interrupt_data->pending_handler = 0;
472     th->interrupt_data->gc_blocked_deferrables = 0;
473     th->no_tls_value_marker=initial_function;
474
475     th->stepping = NIL;
476     return th;
477 }
478
479 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
480 mach_port_t setup_mach_exception_handling_thread();
481 kern_return_t mach_thread_init(mach_port_t thread_exception_port);
482
483 #endif
484
485 void create_initial_thread(lispobj initial_function) {
486     struct thread *th=create_thread_struct(initial_function);
487     if(th) {
488 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
489         setup_mach_exception_handling_thread();
490 #endif
491         initial_thread_trampoline(th); /* no return */
492     } else lose("can't create initial thread\n");
493 }
494
495 #ifdef LISP_FEATURE_SB_THREAD
496
497 #ifndef __USE_XOPEN2K
498 extern int pthread_attr_setstack (pthread_attr_t *__attr, void *__stackaddr,
499                                   size_t __stacksize);
500 #endif
501
502 boolean create_os_thread(struct thread *th,os_thread_t *kid_tid)
503 {
504     /* The new thread inherits the restrictive signal mask set here,
505      * and enables signals again when it is set up properly. */
506     sigset_t oldset;
507     boolean r=1;
508     int retcode = 0, initcode;
509
510     FSHOW_SIGNAL((stderr,"/create_os_thread: creating new thread\n"));
511
512     /* Blocking deferrable signals is enough, no need to block
513      * SIG_STOP_FOR_GC because the child process is not linked onto
514      * all_threads until it's ready. */
515     thread_sigmask(SIG_BLOCK, &deferrable_sigset, &oldset);
516
517 #ifdef LOCK_CREATE_THREAD
518     retcode = pthread_mutex_lock(&create_thread_lock);
519     gc_assert(retcode == 0);
520     FSHOW_SIGNAL((stderr,"/create_os_thread: got lock\n"));
521 #endif
522
523     if((initcode = pthread_attr_init(th->os_attr)) ||
524        /* call_into_lisp_first_time switches the stack for the initial thread. For the
525         * others, we use this. */
526        (pthread_attr_setstack(th->os_attr,th->control_stack_start,thread_control_stack_size)) ||
527        (retcode = pthread_create
528         (kid_tid,th->os_attr,(void *(*)(void *))new_thread_trampoline,th))) {
529         FSHOW_SIGNAL((stderr, "init = %d\n", initcode));
530         FSHOW_SIGNAL((stderr, printf("pthread_create returned %d, errno %d\n", retcode, errno)));
531         if(retcode < 0) {
532             perror("create_os_thread");
533         }
534         r=0;
535     }
536
537 #ifdef LOCK_CREATE_THREAD
538     retcode = pthread_mutex_unlock(&create_thread_lock);
539     gc_assert(retcode == 0);
540     FSHOW_SIGNAL((stderr,"/create_os_thread: released lock\n"));
541 #endif
542     thread_sigmask(SIG_SETMASK,&oldset,0);
543     return r;
544 }
545
546 os_thread_t create_thread(lispobj initial_function) {
547     struct thread *th, *thread = arch_os_get_current_thread();
548     os_thread_t kid_tid = 0;
549
550     /* Must defend against async unwinds. */
551     if (SymbolValue(INTERRUPTS_ENABLED, thread) != NIL)
552         lose("create_thread is not safe when interrupts are enabled.\n");
553     
554     /* Assuming that a fresh thread struct has no lisp objects in it,
555      * linking it to all_threads can be left to the thread itself
556      * without fear of gc lossage. initial_function violates this
557      * assumption and must stay pinned until the child starts up. */
558     th = create_thread_struct(initial_function);
559     if (th && !create_os_thread(th,&kid_tid)) {
560         free_thread_struct(th);
561         kid_tid = 0;
562     }
563     return kid_tid;
564 }
565
566 int signal_interrupt_thread(os_thread_t os_thread)
567 {
568     int status = pthread_kill(os_thread, SIG_INTERRUPT_THREAD);
569     FSHOW_SIGNAL((stderr,"/signal_interrupt_thread: %lu\n", os_thread));
570     if (status == 0) {
571         return 0;
572     } else if (status == ESRCH) {
573         return -1;
574     } else {
575         lose("cannot send SIG_INTERRUPT_THREAD to thread=%lu: %d, %s\n",
576              os_thread, status, strerror(status));
577     }
578 }
579
580 /* stopping the world is a two-stage process.  From this thread we signal
581  * all the others with SIG_STOP_FOR_GC.  The handler for this signal does
582  * the usual pseudo-atomic checks (we don't want to stop a thread while
583  * it's in the middle of allocation) then waits for another SIG_STOP_FOR_GC.
584  */
585
586 /* To avoid deadlocks when gc stops the world all clients of each
587  * mutex must enable or disable SIG_STOP_FOR_GC for the duration of
588  * holding the lock, but they must agree on which. */
589 void gc_stop_the_world()
590 {
591     struct thread *p,*th=arch_os_get_current_thread();
592     int status, lock_ret;
593 #ifdef LOCK_CREATE_THREAD
594     /* KLUDGE: Stopping the thread during pthread_create() causes deadlock
595      * on FreeBSD. */
596     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:waiting on create_thread_lock\n"));
597     lock_ret = pthread_mutex_lock(&create_thread_lock);
598     gc_assert(lock_ret == 0);
599     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:got create_thread_lock\n"));
600 #endif
601     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:waiting on lock\n"));
602     /* keep threads from starting while the world is stopped. */
603     lock_ret = pthread_mutex_lock(&all_threads_lock);      \
604     gc_assert(lock_ret == 0);
605
606     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:got lock\n"));
607     /* stop all other threads by sending them SIG_STOP_FOR_GC */
608     for(p=all_threads; p; p=p->next) {
609         gc_assert(p->os_thread != 0);
610         FSHOW_SIGNAL((stderr,"/gc_stop_the_world: thread=%lu, state=%x\n",
611                       p->os_thread, thread_state(p)));
612         if((p!=th) && ((thread_state(p)==STATE_RUNNING))) {
613             FSHOW_SIGNAL((stderr,"/gc_stop_the_world: suspending thread %lu\n",
614                           p->os_thread));
615             status=pthread_kill(p->os_thread,SIG_STOP_FOR_GC);
616             if (status==ESRCH) {
617                 /* This thread has exited. */
618                 gc_assert(thread_state(p)==STATE_DEAD);
619             } else if (status) {
620                 lose("cannot send suspend thread=%lu: %d, %s\n",
621                      p->os_thread,status,strerror(status));
622             }
623         }
624     }
625     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:signals sent\n"));
626     for(p=all_threads;p;p=p->next) {
627         if (p!=th) {
628             FSHOW_SIGNAL
629                 ((stderr,
630                   "/gc_stop_the_world: waiting for thread=%lu: state=%x\n",
631                   p->os_thread, thread_state(p)));
632             wait_for_thread_state_change(p, STATE_RUNNING);
633             if (p->state == STATE_RUNNING)
634                 lose("/gc_stop_the_world: unexpected state");
635         }
636     }
637     FSHOW_SIGNAL((stderr,"/gc_stop_the_world:end\n"));
638 }
639
640 void gc_start_the_world()
641 {
642     struct thread *p,*th=arch_os_get_current_thread();
643     int lock_ret;
644     /* if a resumed thread creates a new thread before we're done with
645      * this loop, the new thread will get consed on the front of
646      * all_threads, but it won't have been stopped so won't need
647      * restarting */
648     FSHOW_SIGNAL((stderr,"/gc_start_the_world:begin\n"));
649     for(p=all_threads;p;p=p->next) {
650         gc_assert(p->os_thread!=0);
651         if (p!=th) {
652             lispobj state = thread_state(p);
653             if (state != STATE_DEAD) {
654                 if(state != STATE_SUSPENDED) {
655                     lose("gc_start_the_world: wrong thread state is %d\n",
656                          fixnum_value(state));
657                 }
658                 FSHOW_SIGNAL((stderr, "/gc_start_the_world: resuming %lu\n",
659                               p->os_thread));
660                 set_thread_state(p, STATE_RUNNING);
661             }
662         }
663     }
664
665     lock_ret = pthread_mutex_unlock(&all_threads_lock);
666     gc_assert(lock_ret == 0);
667 #ifdef LOCK_CREATE_THREAD
668     lock_ret = pthread_mutex_unlock(&create_thread_lock);
669     gc_assert(lock_ret == 0);
670 #endif
671
672     FSHOW_SIGNAL((stderr,"/gc_start_the_world:end\n"));
673 }
674 #endif
675
676 int
677 thread_yield()
678 {
679 #ifdef LISP_FEATURE_SB_THREAD
680     return sched_yield();
681 #else
682     return 0;
683 #endif
684 }