2 * mono-threads.c: Low-level threading
5 * Rodrigo Kumpera (kumpera@gmail.com)
7 * Copyright 2011 Novell, Inc (http://www.novell.com)
8 * Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
11 #include <mono/utils/mono-compiler.h>
12 #include <mono/utils/mono-semaphore.h>
13 #include <mono/utils/mono-threads.h>
14 #include <mono/utils/mono-tls.h>
15 #include <mono/utils/hazard-pointer.h>
16 #include <mono/utils/mono-memory-model.h>
17 #include <mono/metadata/appdomain.h>
18 #include <mono/metadata/domain-internals.h>
23 #include <mono/utils/mach-support.h>
26 #define THREADS_DEBUG(...)
27 //#define THREADS_DEBUG(...) g_message(__VA_ARGS__)
30 Mutex that makes sure only a single thread can be suspending others.
31 Suspend is a very racy operation since it requires restarting until
32 the target thread is not on an unsafe region.
34 We could implement this using critical regions, but would be much much
35 harder for an operation that is hardly performance critical.
37 The GC has to acquire this lock before starting a STW to make sure
38 a runtime suspend won't make it wronly see a thread in a safepoint
39 when it is in fact not.
41 static MonoSemType global_suspend_semaphore;
43 static int thread_info_size;
44 static MonoThreadInfoCallbacks threads_callbacks;
45 static MonoThreadInfoRuntimeCallbacks runtime_callbacks;
46 static MonoNativeTlsKey thread_info_key, small_id_key;
47 static MonoLinkedListSet thread_list;
48 static gboolean disable_new_interrupt = FALSE;
49 static gboolean mono_threads_inited = FALSE;
51 static void mono_threads_unregister_current_thread (MonoThreadInfo *info);
55 mono_hazard_pointer_clear_all (MonoThreadHazardPointers *hp, int retain)
58 mono_hazard_pointer_clear (hp, 0);
60 mono_hazard_pointer_clear (hp, 1);
62 mono_hazard_pointer_clear (hp, 2);
66 If return non null Hazard Pointer 1 holds the return value.
69 mono_thread_info_lookup (MonoNativeThreadId id)
71 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
73 if (!mono_lls_find (&thread_list, hp, (uintptr_t)id)) {
74 mono_hazard_pointer_clear_all (hp, -1);
78 mono_hazard_pointer_clear_all (hp, 1);
79 return mono_hazard_pointer_get_val (hp, 1);
83 mono_thread_info_insert (MonoThreadInfo *info)
85 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
87 if (!mono_lls_insert (&thread_list, hp, (MonoLinkedListSetNode*)info)) {
88 mono_hazard_pointer_clear_all (hp, -1);
92 mono_hazard_pointer_clear_all (hp, -1);
97 mono_thread_info_remove (MonoThreadInfo *info)
99 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
102 THREADS_DEBUG ("removing info %p\n", info);
103 res = mono_lls_remove (&thread_list, hp, (MonoLinkedListSetNode*)info);
104 mono_hazard_pointer_clear_all (hp, -1);
109 free_thread_info (gpointer mem)
111 MonoThreadInfo *info = mem;
113 MONO_SEM_DESTROY (&info->suspend_semaphore);
114 MONO_SEM_DESTROY (&info->resume_semaphore);
115 MONO_SEM_DESTROY (&info->finish_resume_semaphore);
116 mono_threads_platform_free (info);
122 mono_thread_info_register_small_id (void)
124 int small_id = mono_thread_small_id_alloc ();
125 mono_native_tls_set_value (small_id_key, GUINT_TO_POINTER (small_id + 1));
130 register_thread (MonoThreadInfo *info, gpointer baseptr)
132 int small_id = mono_thread_info_register_small_id ();
134 mono_thread_info_set_tid (info, mono_native_thread_id_get ());
135 info->small_id = small_id;
137 MONO_SEM_INIT (&info->suspend_semaphore, 1);
138 MONO_SEM_INIT (&info->resume_semaphore, 0);
139 MONO_SEM_INIT (&info->finish_resume_semaphore, 0);
141 /*set TLS early so SMR works */
142 mono_native_tls_set_value (thread_info_key, info);
144 THREADS_DEBUG ("registering info %p tid %p small id %x\n", info, mono_thread_info_get_tid (info), info->small_id);
146 if (threads_callbacks.thread_register) {
147 if (threads_callbacks.thread_register (info, baseptr) == NULL) {
148 g_warning ("thread registation failed\n");
154 mono_threads_platform_register (info);
155 info->thread_state = STATE_RUNNING;
156 mono_thread_info_suspend_lock ();
157 /*If this fail it means a given thread has been registered twice, which doesn't make sense. */
158 result = mono_thread_info_insert (info);
160 mono_thread_info_suspend_unlock ();
165 unregister_thread (void *arg)
167 MonoThreadInfo *info = arg;
168 int small_id = info->small_id;
171 THREADS_DEBUG ("unregistering info %p\n", info);
174 * TLS destruction order is not reliable so small_id might be cleaned up
177 mono_native_tls_set_value (small_id_key, GUINT_TO_POINTER (info->small_id + 1));
179 info->thread_state = STATE_SHUTTING_DOWN;
180 mono_thread_info_suspend_lock ();
181 if (threads_callbacks.thread_unregister)
182 threads_callbacks.thread_unregister (info);
183 mono_threads_unregister_current_thread (info);
185 info->thread_state = STATE_DEAD;
186 mono_thread_info_suspend_unlock ();
188 /*now it's safe to free the thread info.*/
189 mono_thread_hazardous_free_or_queue (info, free_thread_info, TRUE, FALSE);
190 mono_thread_small_id_free (small_id);
194 * Removes the current thread from the thread list.
195 * This must be called from the thread unregister callback and nowhere else.
196 * The current thread must be passed as TLS might have already been cleaned up.
199 mono_threads_unregister_current_thread (MonoThreadInfo *info)
202 g_assert (mono_thread_info_get_tid (info) == mono_native_thread_id_get ());
203 result = mono_thread_info_remove (info);
208 mono_thread_info_current (void)
210 MonoThreadInfo *info = (MonoThreadInfo*)mono_native_tls_get_value (thread_info_key);
214 info = mono_thread_info_lookup (mono_native_thread_id_get ()); /*info on HP1*/
217 We might be called during thread cleanup, but we cannot be called after cleanup as happened.
218 The way to distinguish between before, during and after cleanup is the following:
220 -If the TLS key is set, cleanup has not begun;
221 -If the TLS key is clean, but the thread remains registered, cleanup is in progress;
222 -If the thread is nowhere to be found, cleanup has finished.
224 We cannot function after cleanup since there's no way to ensure what will happen.
228 /*We're looking up the current thread which will not be freed until we finish running, so no need to keep it on a HP */
229 mono_hazard_pointer_clear (mono_hazard_pointer_get (), 1);
235 mono_thread_info_get_small_id (void)
237 gpointer val = mono_native_tls_get_value (small_id_key);
240 return GPOINTER_TO_INT (val) - 1;
244 mono_thread_info_list_head (void)
250 mono_thread_info_attach (void *baseptr)
252 MonoThreadInfo *info;
253 if (!mono_threads_inited)
255 /* This can happen from DllMain(DLL_THREAD_ATTACH) on Windows, if a
256 * thread is created before an embedding API user initialized Mono. */
257 THREADS_DEBUG ("mono_thread_info_attach called before mono_threads_init\n");
260 info = mono_native_tls_get_value (thread_info_key);
262 info = g_malloc0 (thread_info_size);
263 THREADS_DEBUG ("attaching %p\n", info);
264 if (!register_thread (info, baseptr))
266 } else if (threads_callbacks.thread_attach) {
267 threads_callbacks.thread_attach (info);
273 mono_thread_info_dettach (void)
275 MonoThreadInfo *info;
276 if (!mono_threads_inited)
278 /* This can happen from DllMain(THREAD_DETACH) on Windows, if a thread
279 * is created before an embedding API user initialized Mono. */
280 THREADS_DEBUG ("mono_thread_info_dettach called before mono_threads_init\n");
283 info = mono_native_tls_get_value (thread_info_key);
285 THREADS_DEBUG ("detaching %p\n", info);
286 unregister_thread (info);
287 mono_native_tls_set_value (thread_info_key, NULL);
292 mono_threads_init (MonoThreadInfoCallbacks *callbacks, size_t info_size)
295 threads_callbacks = *callbacks;
296 thread_info_size = info_size;
298 res = mono_native_tls_alloc (&thread_info_key, NULL);
300 res = mono_native_tls_alloc (&thread_info_key, unregister_thread);
304 res = mono_native_tls_alloc (&small_id_key, NULL);
307 MONO_SEM_INIT (&global_suspend_semaphore, 1);
309 mono_lls_init (&thread_list, NULL);
310 mono_thread_smr_init ();
311 mono_threads_init_platform ();
313 #if defined(__MACH__)
314 mono_mach_init (thread_info_key);
317 mono_threads_inited = TRUE;
319 g_assert (sizeof (MonoNativeThreadId) <= sizeof (uintptr_t));
323 mono_threads_runtime_init (MonoThreadInfoRuntimeCallbacks *callbacks)
325 runtime_callbacks = *callbacks;
328 MonoThreadInfoCallbacks *
329 mono_threads_get_callbacks (void)
331 return &threads_callbacks;
334 MonoThreadInfoRuntimeCallbacks *
335 mono_threads_get_runtime_callbacks (void)
337 return &runtime_callbacks;
341 The return value is only valid until a matching mono_thread_info_resume is called
343 static MonoThreadInfo*
344 mono_thread_info_suspend_sync (MonoNativeThreadId tid, gboolean interrupt_kernel)
346 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
347 MonoThreadInfo *info = mono_thread_info_lookup (tid); /*info on HP1*/
351 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore);
353 /*thread is on the process of detaching*/
354 if (mono_thread_info_run_state (info) > STATE_RUNNING) {
355 mono_hazard_pointer_clear (hp, 1);
359 THREADS_DEBUG ("suspend %x IN COUNT %d\n", tid, info->suspend_count);
361 if (info->suspend_count) {
362 ++info->suspend_count;
363 mono_hazard_pointer_clear (hp, 1);
364 MONO_SEM_POST (&info->suspend_semaphore);
368 if (!mono_threads_core_suspend (info)) {
369 MONO_SEM_POST (&info->suspend_semaphore);
370 mono_hazard_pointer_clear (hp, 1);
374 if (interrupt_kernel)
375 mono_threads_core_interrupt (info);
377 ++info->suspend_count;
378 info->thread_state |= STATE_SUSPENDED;
379 MONO_SEM_POST (&info->suspend_semaphore);
380 mono_hazard_pointer_clear (hp, 1);
386 mono_thread_info_self_suspend (void)
389 MonoThreadInfo *info = mono_thread_info_current ();
393 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore);
395 THREADS_DEBUG ("self suspend IN COUNT %d\n", info->suspend_count);
397 g_assert (info->suspend_count == 0);
398 ++info->suspend_count;
400 info->thread_state |= STATE_SELF_SUSPENDED;
402 ret = mono_threads_get_runtime_callbacks ()->thread_state_init_from_sigctx (&info->suspend_state, NULL);
405 MONO_SEM_POST (&info->suspend_semaphore);
407 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->resume_semaphore);
409 g_assert (!info->async_target); /*FIXME this should happen normally for suspend. */
410 MONO_SEM_POST (&info->finish_resume_semaphore);
414 mono_thread_info_resume_internal (MonoThreadInfo *info)
417 if (mono_thread_info_suspend_state (info) == STATE_SELF_SUSPENDED) {
418 MONO_SEM_POST (&info->resume_semaphore);
419 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->finish_resume_semaphore);
422 result = mono_threads_core_resume (info);
424 info->thread_state &= ~SUSPEND_STATE_MASK;
429 mono_thread_info_resume (MonoNativeThreadId tid)
431 gboolean result = TRUE;
432 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
433 MonoThreadInfo *info = mono_thread_info_lookup (tid); /*info on HP1*/
437 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore);
439 THREADS_DEBUG ("resume %x IN COUNT %d\n",tid, info->suspend_count);
441 if (info->suspend_count <= 0) {
442 MONO_SEM_POST (&info->suspend_semaphore);
443 mono_hazard_pointer_clear (hp, 1);
448 * The theory here is that if we manage to suspend the thread it means it did not
449 * start cleanup since it take the same lock.
451 g_assert (mono_thread_info_get_tid (info));
453 if (--info->suspend_count == 0)
454 result = mono_thread_info_resume_internal (info);
456 MONO_SEM_POST (&info->suspend_semaphore);
457 mono_hazard_pointer_clear (hp, 1);
458 mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, FALSE);
464 mono_thread_info_finish_suspend (void)
466 mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, FALSE);
470 FIXME fix cardtable WB to be out of line and check with the runtime if the target is not the
471 WB trampoline. Another option is to encode wb ranges in MonoJitInfo, but that is somewhat hard.
474 is_thread_in_critical_region (MonoThreadInfo *info)
479 if (info->inside_critical_region)
482 ji = mono_jit_info_table_find (
483 info->suspend_state.unwind_data [MONO_UNWIND_DATA_DOMAIN],
484 MONO_CONTEXT_GET_IP (&info->suspend_state.ctx));
489 method = mono_jit_info_get_method (ji);
491 return threads_callbacks.mono_method_is_critical (method);
496 If we are trying to suspend a target that is on a critical region
497 and running a syscall we risk looping forever if @interrupt_kernel is FALSE.
498 So, be VERY carefull in calling this with @interrupt_kernel == FALSE.
501 mono_thread_info_safe_suspend_sync (MonoNativeThreadId id, gboolean interrupt_kernel)
503 MonoThreadInfo *info = NULL;
504 int sleep_duration = 0;
506 /*FIXME: unify this with self-suspend*/
507 g_assert (id != mono_native_thread_id_get ());
509 mono_thread_info_suspend_lock ();
512 if (!(info = mono_thread_info_suspend_sync (id, interrupt_kernel))) {
513 g_warning ("failed to suspend thread %p, hopefully it is dead", (gpointer)id);
514 mono_thread_info_suspend_unlock ();
517 /*WARNING: We now are in interrupt context until we resume the thread. */
518 if (!is_thread_in_critical_region (info))
521 if (!mono_thread_info_resume (id)) {
522 g_warning ("failed to result thread %p, hopefully it is dead", (gpointer)id);
523 mono_thread_info_suspend_unlock ();
526 THREADS_DEBUG ("restarted thread %p\n", (gpointer)id);
528 if (!sleep_duration) {
536 g_usleep (sleep_duration);
538 sleep_duration += 10;
541 mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, TRUE);
543 mono_thread_info_suspend_unlock ();
548 Inject an assynchronous call into the target thread. The target thread must be suspended and
549 only a single async call can be setup for a given suspend cycle.
550 This async call must cause stack unwinding as the current implementation doesn't save enough state
551 to resume execution of the top-of-stack function. It's an acceptable limitation since this is
552 currently used only to deliver exceptions.
555 mono_thread_info_setup_async_call (MonoThreadInfo *info, void (*target_func)(void*), void *user_data)
557 g_assert (info->suspend_count);
558 /*FIXME this is a bad assert, we probably should do proper locking and fail if one is already set*/
559 g_assert (!info->async_target);
560 info->async_target = target_func;
561 /* This is not GC tracked */
562 info->user_data = user_data;
566 The suspend lock is held during any suspend in progress.
567 A GC that has safepoints must take this lock as part of its
568 STW to make sure no unsafe pending suspend is in progress.
571 mono_thread_info_suspend_lock (void)
573 MONO_SEM_WAIT_UNITERRUPTIBLE (&global_suspend_semaphore);
577 mono_thread_info_suspend_unlock (void)
579 MONO_SEM_POST (&global_suspend_semaphore);
583 mono_thread_info_disable_new_interrupt (gboolean disable)
585 disable_new_interrupt = disable;
589 * This is a very specific function whose only purpose is to
590 * break a given thread from socket syscalls.
592 * This only exists because linux won't fail a call to connect
593 * if the underlying is closed.
595 * TODO We should cleanup and unify this with the other syscall abort
599 mono_thread_info_abort_socket_syscall_for_close (MonoNativeThreadId tid)
601 MonoThreadHazardPointers *hp;
602 MonoThreadInfo *info;
604 if (tid == mono_native_thread_id_get () || !mono_threads_core_needs_abort_syscall ())
607 hp = mono_hazard_pointer_get ();
608 info = mono_thread_info_lookup (tid); /*info on HP1*/
612 if (mono_thread_info_run_state (info) > STATE_RUNNING) {
613 mono_hazard_pointer_clear (hp, 1);
617 mono_thread_info_suspend_lock ();
619 mono_threads_core_abort_syscall (info);
621 mono_hazard_pointer_clear (hp, 1);
622 mono_thread_info_suspend_unlock ();
626 Disabled by default for now.
627 To enable this we need mini to implement the callbacks by MonoThreadInfoRuntimeCallbacks
628 which means mono-context and setup_async_callback, and we need a mono-threads backend.
631 mono_thread_info_new_interrupt_enabled (void)
633 /*We need STW gc events to work correctly*/
634 #if defined (HAVE_BOEHM_GC) && !defined (USE_INCLUDED_LIBGC)
638 #if defined(HOST_WIN32)
641 #if defined (__i386__)
642 return !disable_new_interrupt;
648 * mono_thread_info_set_is_async_context:
650 * Set whenever the current thread is in an async context. Some runtime functions might behave
651 * differently while in an async context in order to be async safe.
654 mono_thread_info_set_is_async_context (gboolean async_context)
656 MonoThreadInfo *info = mono_thread_info_current ();
659 info->is_async_context = async_context;
663 mono_thread_info_is_async_context (void)
665 MonoThreadInfo *info = mono_thread_info_current ();
668 return info->is_async_context;