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>
21 #include <mono/utils/mach-support.h>
24 #define THREADS_DEBUG(...)
25 //#define THREADS_DEBUG(...) g_message(__VA_ARGS__)
28 Mutex that makes sure only a single thread can be suspending others.
29 Suspend is a very racy operation since it requires restarting until
30 the target thread is not on an unsafe region.
32 We could implement this using critical regions, but would be much much
33 harder for an operation that is hardly performance critical.
35 The GC has to acquire this lock before starting a STW to make sure
36 a runtime suspend won't make it wronly see a thread in a safepoint
37 when it is in fact not.
39 static MonoSemType global_suspend_semaphore;
41 static size_t thread_info_size;
42 static MonoThreadInfoCallbacks threads_callbacks;
43 static MonoThreadInfoRuntimeCallbacks runtime_callbacks;
44 static MonoNativeTlsKey thread_info_key, small_id_key;
45 static MonoLinkedListSet thread_list;
46 static gboolean disable_new_interrupt = FALSE;
47 static gboolean mono_threads_inited = FALSE;
49 static void mono_threads_unregister_current_thread (MonoThreadInfo *info);
53 mono_hazard_pointer_clear_all (MonoThreadHazardPointers *hp, int retain)
56 mono_hazard_pointer_clear (hp, 0);
58 mono_hazard_pointer_clear (hp, 1);
60 mono_hazard_pointer_clear (hp, 2);
64 If return non null Hazard Pointer 1 holds the return value.
67 mono_thread_info_lookup (MonoNativeThreadId id)
69 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
71 if (!mono_lls_find (&thread_list, hp, (uintptr_t)id)) {
72 mono_hazard_pointer_clear_all (hp, -1);
76 mono_hazard_pointer_clear_all (hp, 1);
77 return mono_hazard_pointer_get_val (hp, 1);
81 mono_thread_info_insert (MonoThreadInfo *info)
83 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
85 if (!mono_lls_insert (&thread_list, hp, (MonoLinkedListSetNode*)info)) {
86 mono_hazard_pointer_clear_all (hp, -1);
90 mono_hazard_pointer_clear_all (hp, -1);
95 mono_thread_info_remove (MonoThreadInfo *info)
97 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
100 THREADS_DEBUG ("removing info %p\n", info);
101 res = mono_lls_remove (&thread_list, hp, (MonoLinkedListSetNode*)info);
102 mono_hazard_pointer_clear_all (hp, -1);
107 free_thread_info (gpointer mem)
109 MonoThreadInfo *info = mem;
111 MONO_SEM_DESTROY (&info->suspend_semaphore);
112 MONO_SEM_DESTROY (&info->resume_semaphore);
113 MONO_SEM_DESTROY (&info->finish_resume_semaphore);
114 mono_threads_platform_free (info);
120 mono_thread_info_register_small_id (void)
122 int small_id = mono_thread_small_id_alloc ();
123 mono_native_tls_set_value (small_id_key, GUINT_TO_POINTER (small_id + 1));
128 register_thread (MonoThreadInfo *info, gpointer baseptr)
130 int small_id = mono_thread_info_register_small_id ();
132 mono_thread_info_set_tid (info, mono_native_thread_id_get ());
133 info->small_id = small_id;
135 MONO_SEM_INIT (&info->suspend_semaphore, 1);
136 MONO_SEM_INIT (&info->resume_semaphore, 0);
137 MONO_SEM_INIT (&info->finish_resume_semaphore, 0);
139 /*set TLS early so SMR works */
140 mono_native_tls_set_value (thread_info_key, info);
142 THREADS_DEBUG ("registering info %p tid %p small id %x\n", info, mono_thread_info_get_tid (info), info->small_id);
144 if (threads_callbacks.thread_register) {
145 if (threads_callbacks.thread_register (info, baseptr) == NULL) {
146 g_warning ("thread registation failed\n");
152 mono_threads_platform_register (info);
153 info->thread_state = STATE_RUNNING;
154 mono_thread_info_suspend_lock ();
155 /*If this fail it means a given thread has been registered twice, which doesn't make sense. */
156 result = mono_thread_info_insert (info);
158 mono_thread_info_suspend_unlock ();
163 unregister_thread (void *arg)
165 MonoThreadInfo *info = arg;
166 int small_id = info->small_id;
169 THREADS_DEBUG ("unregistering info %p\n", info);
171 mono_threads_core_unregister (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;
182 First perform the callback that requires no locks.
183 This callback has the potential of taking other locks, so we do it before.
184 After it completes, the thread remains functional.
186 if (threads_callbacks.thread_detach)
187 threads_callbacks.thread_detach (info);
189 mono_thread_info_suspend_lock ();
192 Now perform the callback that must be done under locks.
193 This will render the thread useless and non-suspendable, so it must
194 be done while holding the suspend lock to give no other thread chance
197 if (threads_callbacks.thread_unregister)
198 threads_callbacks.thread_unregister (info);
199 mono_threads_unregister_current_thread (info);
201 info->thread_state = STATE_DEAD;
202 mono_thread_info_suspend_unlock ();
204 /*now it's safe to free the thread info.*/
205 mono_thread_hazardous_free_or_queue (info, free_thread_info, TRUE, FALSE);
206 mono_thread_small_id_free (small_id);
210 * Removes the current thread from the thread list.
211 * This must be called from the thread unregister callback and nowhere else.
212 * The current thread must be passed as TLS might have already been cleaned up.
215 mono_threads_unregister_current_thread (MonoThreadInfo *info)
218 g_assert (mono_thread_info_get_tid (info) == mono_native_thread_id_get ());
219 result = mono_thread_info_remove (info);
224 mono_thread_info_current (void)
226 MonoThreadInfo *info = (MonoThreadInfo*)mono_native_tls_get_value (thread_info_key);
230 info = mono_thread_info_lookup (mono_native_thread_id_get ()); /*info on HP1*/
233 We might be called during thread cleanup, but we cannot be called after cleanup as happened.
234 The way to distinguish between before, during and after cleanup is the following:
236 -If the TLS key is set, cleanup has not begun;
237 -If the TLS key is clean, but the thread remains registered, cleanup is in progress;
238 -If the thread is nowhere to be found, cleanup has finished.
240 We cannot function after cleanup since there's no way to ensure what will happen.
244 /*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 */
245 mono_hazard_pointer_clear (mono_hazard_pointer_get (), 1);
251 mono_thread_info_get_small_id (void)
253 gpointer val = mono_native_tls_get_value (small_id_key);
256 return GPOINTER_TO_INT (val) - 1;
260 mono_thread_info_list_head (void)
266 mono_thread_info_attach (void *baseptr)
268 MonoThreadInfo *info;
269 if (!mono_threads_inited)
271 /* This can happen from DllMain(DLL_THREAD_ATTACH) on Windows, if a
272 * thread is created before an embedding API user initialized Mono. */
273 THREADS_DEBUG ("mono_thread_info_attach called before mono_threads_init\n");
276 info = mono_native_tls_get_value (thread_info_key);
278 info = g_malloc0 (thread_info_size);
279 THREADS_DEBUG ("attaching %p\n", info);
280 if (!register_thread (info, baseptr))
282 } else if (threads_callbacks.thread_attach) {
283 threads_callbacks.thread_attach (info);
289 mono_thread_info_detach (void)
291 MonoThreadInfo *info;
292 if (!mono_threads_inited)
294 /* This can happen from DllMain(THREAD_DETACH) on Windows, if a thread
295 * is created before an embedding API user initialized Mono. */
296 THREADS_DEBUG ("mono_thread_info_detach called before mono_threads_init\n");
299 info = mono_native_tls_get_value (thread_info_key);
301 THREADS_DEBUG ("detaching %p\n", info);
302 unregister_thread (info);
303 mono_native_tls_set_value (thread_info_key, NULL);
308 mono_threads_init (MonoThreadInfoCallbacks *callbacks, size_t info_size)
311 threads_callbacks = *callbacks;
312 thread_info_size = info_size;
314 res = mono_native_tls_alloc (&thread_info_key, NULL);
316 res = mono_native_tls_alloc (&thread_info_key, unregister_thread);
320 res = mono_native_tls_alloc (&small_id_key, NULL);
323 MONO_SEM_INIT (&global_suspend_semaphore, 1);
325 mono_lls_init (&thread_list, NULL);
326 mono_thread_smr_init ();
327 mono_threads_init_platform ();
329 #if defined(__MACH__)
330 mono_mach_init (thread_info_key);
333 mono_threads_inited = TRUE;
335 g_assert (sizeof (MonoNativeThreadId) <= sizeof (uintptr_t));
339 mono_threads_runtime_init (MonoThreadInfoRuntimeCallbacks *callbacks)
341 runtime_callbacks = *callbacks;
344 MonoThreadInfoCallbacks *
345 mono_threads_get_callbacks (void)
347 return &threads_callbacks;
350 MonoThreadInfoRuntimeCallbacks *
351 mono_threads_get_runtime_callbacks (void)
353 return &runtime_callbacks;
357 The return value is only valid until a matching mono_thread_info_resume is called
359 static MonoThreadInfo*
360 mono_thread_info_suspend_sync (MonoNativeThreadId tid, gboolean interrupt_kernel)
362 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
363 MonoThreadInfo *info = mono_thread_info_lookup (tid); /*info on HP1*/
367 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore);
369 /*thread is on the process of detaching*/
370 if (mono_thread_info_run_state (info) > STATE_RUNNING) {
371 mono_hazard_pointer_clear (hp, 1);
375 THREADS_DEBUG ("suspend %x IN COUNT %d\n", tid, info->suspend_count);
377 if (info->suspend_count) {
378 ++info->suspend_count;
379 mono_hazard_pointer_clear (hp, 1);
380 MONO_SEM_POST (&info->suspend_semaphore);
384 if (!mono_threads_core_suspend (info)) {
385 MONO_SEM_POST (&info->suspend_semaphore);
386 mono_hazard_pointer_clear (hp, 1);
390 if (interrupt_kernel)
391 mono_threads_core_interrupt (info);
393 ++info->suspend_count;
394 info->thread_state |= STATE_SUSPENDED;
395 MONO_SEM_POST (&info->suspend_semaphore);
401 mono_thread_info_self_suspend (void)
404 MonoThreadInfo *info = mono_thread_info_current ();
408 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore);
410 THREADS_DEBUG ("self suspend IN COUNT %d\n", info->suspend_count);
412 g_assert (info->suspend_count == 0);
413 ++info->suspend_count;
415 info->thread_state |= STATE_SELF_SUSPENDED;
417 ret = mono_threads_get_runtime_callbacks ()->thread_state_init_from_sigctx (&info->suspend_state, NULL);
420 MONO_SEM_POST (&info->suspend_semaphore);
422 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->resume_semaphore);
424 g_assert (!info->async_target); /*FIXME this should happen normally for suspend. */
425 MONO_SEM_POST (&info->finish_resume_semaphore);
429 mono_thread_info_core_resume (MonoThreadInfo *info)
432 MonoNativeThreadId tid = mono_thread_info_get_tid (info);
433 if (info->create_suspended) {
434 /* Have to special case this, as the normal suspend/resume pair are racy, they don't work if he resume is received before the suspend */
435 info->create_suspended = FALSE;
436 mono_threads_core_resume_created (info, tid);
440 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore);
442 THREADS_DEBUG ("resume %x IN COUNT %d\n", tid, info->suspend_count);
444 if (info->suspend_count <= 0) {
445 MONO_SEM_POST (&info->suspend_semaphore);
450 * The theory here is that if we manage to suspend the thread it means it did not
451 * start cleanup since it take the same lock.
453 g_assert (mono_thread_info_get_tid (info));
455 if (--info->suspend_count == 0) {
456 if (mono_thread_info_suspend_state (info) == STATE_SELF_SUSPENDED) {
457 MONO_SEM_POST (&info->resume_semaphore);
458 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->finish_resume_semaphore);
461 result = mono_threads_core_resume (info);
463 info->thread_state &= ~SUSPEND_STATE_MASK;
468 MONO_SEM_POST (&info->suspend_semaphore);
473 mono_thread_info_resume (MonoNativeThreadId tid)
475 gboolean result; /* don't initialize it so the compiler can catch unitilized paths. */
476 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
477 MonoThreadInfo *info = mono_thread_info_lookup (tid); /*info on HP1*/
483 result = mono_thread_info_core_resume (info);
486 mono_hazard_pointer_clear (hp, 1);
491 mono_thread_info_finish_suspend (MonoThreadInfo *info)
493 mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, FALSE);
497 mono_thread_info_finish_suspend_and_resume (MonoThreadInfo *info)
499 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
501 /*Resume can access info after the target has resumed, so we must ensure it won't touch freed memory. */
502 mono_hazard_pointer_set (hp, 1, info);
503 mono_thread_info_core_resume (info);
504 mono_hazard_pointer_clear (hp, 1);
506 mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, FALSE);
510 FIXME fix cardtable WB to be out of line and check with the runtime if the target is not the
511 WB trampoline. Another option is to encode wb ranges in MonoJitInfo, but that is somewhat hard.
514 is_thread_in_critical_region (MonoThreadInfo *info)
519 if (info->inside_critical_region)
522 /* The target thread might be shutting down and the domain might be null, which means no managed code left to run. */
523 if (!info->suspend_state.unwind_data [MONO_UNWIND_DATA_DOMAIN])
526 ji = mono_jit_info_table_find (
527 info->suspend_state.unwind_data [MONO_UNWIND_DATA_DOMAIN],
528 MONO_CONTEXT_GET_IP (&info->suspend_state.ctx));
533 method = mono_jit_info_get_method (ji);
535 return threads_callbacks.mono_method_is_critical (method);
540 If we are trying to suspend a target that is on a critical region
541 and running a syscall we risk looping forever if @interrupt_kernel is FALSE.
542 So, be VERY carefull in calling this with @interrupt_kernel == FALSE.
544 Info is not put on a hazard pointer as a suspended thread cannot exit and be freed.
546 This function MUST be matched with mono_thread_info_finish_suspend or mono_thread_info_finish_suspend_and_resume
549 mono_thread_info_safe_suspend_sync (MonoNativeThreadId id, gboolean interrupt_kernel)
551 MonoThreadInfo *info = NULL;
552 int sleep_duration = 0;
554 /*FIXME: unify this with self-suspend*/
555 g_assert (id != mono_native_thread_id_get ());
557 mono_thread_info_suspend_lock ();
560 if (!(info = mono_thread_info_suspend_sync (id, interrupt_kernel))) {
561 g_warning ("failed to suspend thread %p, hopefully it is dead", (gpointer)id);
562 mono_thread_info_suspend_unlock ();
565 /*WARNING: We now are in interrupt context until we resume the thread. */
566 if (!is_thread_in_critical_region (info))
569 if (!mono_thread_info_core_resume (info)) {
570 g_warning ("failed to result thread %p, hopefully it is dead", (gpointer)id);
571 mono_hazard_pointer_clear (mono_hazard_pointer_get (), 1);
572 mono_thread_info_suspend_unlock ();
575 THREADS_DEBUG ("restarted thread %p\n", (gpointer)id);
577 if (!sleep_duration) {
585 g_usleep (sleep_duration);
587 sleep_duration += 10;
590 /* XXX this clears HP 1, so we restated it again */
591 mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, TRUE);
592 mono_thread_info_suspend_unlock ();
598 Inject an assynchronous call into the target thread. The target thread must be suspended and
599 only a single async call can be setup for a given suspend cycle.
600 This async call must cause stack unwinding as the current implementation doesn't save enough state
601 to resume execution of the top-of-stack function. It's an acceptable limitation since this is
602 currently used only to deliver exceptions.
605 mono_thread_info_setup_async_call (MonoThreadInfo *info, void (*target_func)(void*), void *user_data)
607 g_assert (info->suspend_count);
608 /*FIXME this is a bad assert, we probably should do proper locking and fail if one is already set*/
609 g_assert (!info->async_target);
610 info->async_target = target_func;
611 /* This is not GC tracked */
612 info->user_data = user_data;
616 The suspend lock is held during any suspend in progress.
617 A GC that has safepoints must take this lock as part of its
618 STW to make sure no unsafe pending suspend is in progress.
621 mono_thread_info_suspend_lock (void)
623 MONO_SEM_WAIT_UNITERRUPTIBLE (&global_suspend_semaphore);
627 mono_thread_info_suspend_unlock (void)
629 MONO_SEM_POST (&global_suspend_semaphore);
633 mono_thread_info_disable_new_interrupt (gboolean disable)
635 disable_new_interrupt = disable;
639 * This is a very specific function whose only purpose is to
640 * break a given thread from socket syscalls.
642 * This only exists because linux won't fail a call to connect
643 * if the underlying is closed.
645 * TODO We should cleanup and unify this with the other syscall abort
649 mono_thread_info_abort_socket_syscall_for_close (MonoNativeThreadId tid)
651 MonoThreadHazardPointers *hp;
652 MonoThreadInfo *info;
654 if (tid == mono_native_thread_id_get () || !mono_threads_core_needs_abort_syscall ())
657 hp = mono_hazard_pointer_get ();
658 info = mono_thread_info_lookup (tid); /*info on HP1*/
662 if (mono_thread_info_run_state (info) > STATE_RUNNING) {
663 mono_hazard_pointer_clear (hp, 1);
667 mono_thread_info_suspend_lock ();
669 mono_threads_core_abort_syscall (info);
671 mono_hazard_pointer_clear (hp, 1);
672 mono_thread_info_suspend_unlock ();
676 Disabled by default for now.
677 To enable this we need mini to implement the callbacks by MonoThreadInfoRuntimeCallbacks
678 which means mono-context and setup_async_callback, and we need a mono-threads backend.
681 mono_thread_info_new_interrupt_enabled (void)
683 /*We need STW gc events to work correctly*/
684 #if defined (HAVE_BOEHM_GC) && !defined (USE_INCLUDED_LIBGC)
688 #if defined(HOST_WIN32)
691 #if defined (__i386__)
692 return !disable_new_interrupt;
698 * mono_thread_info_set_is_async_context:
700 * Set whenever the current thread is in an async context. Some runtime functions might behave
701 * differently while in an async context in order to be async safe.
704 mono_thread_info_set_is_async_context (gboolean async_context)
706 MonoThreadInfo *info = mono_thread_info_current ();
709 info->is_async_context = async_context;
713 mono_thread_info_is_async_context (void)
715 MonoThreadInfo *info = mono_thread_info_current ();
718 return info->is_async_context;
724 * mono_threads_create_thread:
726 * Create a new thread executing START with argument ARG. Store its id into OUT_TID.
727 * Returns: a windows or io-layer handle for the thread.
730 mono_threads_create_thread (LPTHREAD_START_ROUTINE start, gpointer arg, guint32 stack_size, guint32 creation_flags, MonoNativeThreadId *out_tid)
732 return mono_threads_core_create_thread (start, arg, stack_size, creation_flags, out_tid);
736 * mono_thread_info_get_stack_bounds:
738 * Return the address and size of the current threads stack. Return NULL as the
739 * stack address if the stack address cannot be determined.
742 mono_thread_info_get_stack_bounds (guint8 **staddr, size_t *stsize)
744 mono_threads_core_get_stack_bounds (staddr, stsize);
748 mono_thread_info_yield (void)
750 return mono_threads_core_yield ();
754 mono_thread_info_tls_get (THREAD_INFO_TYPE *info, MonoTlsKey key)
756 return ((MonoThreadInfo*)info)->tls [key];
760 * mono_threads_info_tls_set:
762 * Set the TLS key to VALUE in the info structure. This can be used to obtain
763 * values of TLS variables for threads other than the current thread.
764 * This should only be used for infrequently changing TLS variables, and it should
765 * be paired with setting the real TLS variable since this provides no GC tracking.
768 mono_thread_info_tls_set (THREAD_INFO_TYPE *info, MonoTlsKey key, gpointer value)
770 ((MonoThreadInfo*)info)->tls [key] = value;
774 * mono_thread_info_exit:
776 * Exit the current thread.
777 * This function doesn't return.
780 mono_thread_info_exit (void)
782 mono_threads_core_exit (0);
786 * mono_thread_info_open_handle:
788 * Return a io-layer/win32 handle for the current thread.
789 * The handle need to be closed by calling CloseHandle () when it is no
793 mono_thread_info_open_handle (void)
795 return mono_threads_core_open_handle ();
799 * mono_thread_info_open_handle:
801 * Return a io-layer/win32 handle for the thread identified by HANDLE/TID.
802 * The handle need to be closed by calling CloseHandle () when it is no
806 mono_threads_open_thread_handle (HANDLE handle, MonoNativeThreadId tid)
808 return mono_threads_core_open_thread_handle (handle, tid);
812 mono_thread_info_set_name (MonoNativeThreadId tid, const char *name)
814 mono_threads_core_set_name (tid, name);