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;
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_dettach (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_dettach 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);
396 mono_hazard_pointer_clear (hp, 1);
402 mono_thread_info_self_suspend (void)
405 MonoThreadInfo *info = mono_thread_info_current ();
409 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore);
411 THREADS_DEBUG ("self suspend IN COUNT %d\n", info->suspend_count);
413 g_assert (info->suspend_count == 0);
414 ++info->suspend_count;
416 info->thread_state |= STATE_SELF_SUSPENDED;
418 ret = mono_threads_get_runtime_callbacks ()->thread_state_init_from_sigctx (&info->suspend_state, NULL);
421 MONO_SEM_POST (&info->suspend_semaphore);
423 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->resume_semaphore);
425 g_assert (!info->async_target); /*FIXME this should happen normally for suspend. */
426 MONO_SEM_POST (&info->finish_resume_semaphore);
430 mono_thread_info_resume_internal (MonoThreadInfo *info)
433 if (mono_thread_info_suspend_state (info) == STATE_SELF_SUSPENDED) {
434 MONO_SEM_POST (&info->resume_semaphore);
435 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->finish_resume_semaphore);
438 result = mono_threads_core_resume (info);
440 info->thread_state &= ~SUSPEND_STATE_MASK;
445 mono_thread_info_resume (MonoNativeThreadId tid)
447 gboolean result = TRUE;
448 MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
449 MonoThreadInfo *info = mono_thread_info_lookup (tid); /*info on HP1*/
454 if (info->create_suspended) {
455 /* 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 */
456 info->create_suspended = FALSE;
457 mono_threads_core_resume_created (info, tid);
461 MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore);
463 THREADS_DEBUG ("resume %x IN COUNT %d\n",tid, info->suspend_count);
465 if (info->suspend_count <= 0) {
466 MONO_SEM_POST (&info->suspend_semaphore);
467 mono_hazard_pointer_clear (hp, 1);
472 * The theory here is that if we manage to suspend the thread it means it did not
473 * start cleanup since it take the same lock.
475 g_assert (mono_thread_info_get_tid (info));
477 if (--info->suspend_count == 0)
478 result = mono_thread_info_resume_internal (info);
480 MONO_SEM_POST (&info->suspend_semaphore);
481 mono_hazard_pointer_clear (hp, 1);
482 mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, FALSE);
488 mono_thread_info_finish_suspend (void)
490 mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, FALSE);
494 FIXME fix cardtable WB to be out of line and check with the runtime if the target is not the
495 WB trampoline. Another option is to encode wb ranges in MonoJitInfo, but that is somewhat hard.
498 is_thread_in_critical_region (MonoThreadInfo *info)
503 if (info->inside_critical_region)
506 /* The target thread might be shutting down and the domain might be null, which means no managed code left to run. */
507 if (!info->suspend_state.unwind_data [MONO_UNWIND_DATA_DOMAIN])
510 ji = mono_jit_info_table_find (
511 info->suspend_state.unwind_data [MONO_UNWIND_DATA_DOMAIN],
512 MONO_CONTEXT_GET_IP (&info->suspend_state.ctx));
517 method = mono_jit_info_get_method (ji);
519 return threads_callbacks.mono_method_is_critical (method);
524 If we are trying to suspend a target that is on a critical region
525 and running a syscall we risk looping forever if @interrupt_kernel is FALSE.
526 So, be VERY carefull in calling this with @interrupt_kernel == FALSE.
529 mono_thread_info_safe_suspend_sync (MonoNativeThreadId id, gboolean interrupt_kernel)
531 MonoThreadInfo *info = NULL;
532 int sleep_duration = 0;
534 /*FIXME: unify this with self-suspend*/
535 g_assert (id != mono_native_thread_id_get ());
537 mono_thread_info_suspend_lock ();
540 if (!(info = mono_thread_info_suspend_sync (id, interrupt_kernel))) {
541 g_warning ("failed to suspend thread %p, hopefully it is dead", (gpointer)id);
542 mono_thread_info_suspend_unlock ();
545 /*WARNING: We now are in interrupt context until we resume the thread. */
546 if (!is_thread_in_critical_region (info))
549 if (!mono_thread_info_resume (id)) {
550 g_warning ("failed to result thread %p, hopefully it is dead", (gpointer)id);
551 mono_thread_info_suspend_unlock ();
554 THREADS_DEBUG ("restarted thread %p\n", (gpointer)id);
556 if (!sleep_duration) {
564 g_usleep (sleep_duration);
566 sleep_duration += 10;
569 mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, TRUE);
571 mono_thread_info_suspend_unlock ();
576 Inject an assynchronous call into the target thread. The target thread must be suspended and
577 only a single async call can be setup for a given suspend cycle.
578 This async call must cause stack unwinding as the current implementation doesn't save enough state
579 to resume execution of the top-of-stack function. It's an acceptable limitation since this is
580 currently used only to deliver exceptions.
583 mono_thread_info_setup_async_call (MonoThreadInfo *info, void (*target_func)(void*), void *user_data)
585 g_assert (info->suspend_count);
586 /*FIXME this is a bad assert, we probably should do proper locking and fail if one is already set*/
587 g_assert (!info->async_target);
588 info->async_target = target_func;
589 /* This is not GC tracked */
590 info->user_data = user_data;
594 The suspend lock is held during any suspend in progress.
595 A GC that has safepoints must take this lock as part of its
596 STW to make sure no unsafe pending suspend is in progress.
599 mono_thread_info_suspend_lock (void)
601 MONO_SEM_WAIT_UNITERRUPTIBLE (&global_suspend_semaphore);
605 mono_thread_info_suspend_unlock (void)
607 MONO_SEM_POST (&global_suspend_semaphore);
611 mono_thread_info_disable_new_interrupt (gboolean disable)
613 disable_new_interrupt = disable;
617 * This is a very specific function whose only purpose is to
618 * break a given thread from socket syscalls.
620 * This only exists because linux won't fail a call to connect
621 * if the underlying is closed.
623 * TODO We should cleanup and unify this with the other syscall abort
627 mono_thread_info_abort_socket_syscall_for_close (MonoNativeThreadId tid)
629 MonoThreadHazardPointers *hp;
630 MonoThreadInfo *info;
632 if (tid == mono_native_thread_id_get () || !mono_threads_core_needs_abort_syscall ())
635 hp = mono_hazard_pointer_get ();
636 info = mono_thread_info_lookup (tid); /*info on HP1*/
640 if (mono_thread_info_run_state (info) > STATE_RUNNING) {
641 mono_hazard_pointer_clear (hp, 1);
645 mono_thread_info_suspend_lock ();
647 mono_threads_core_abort_syscall (info);
649 mono_hazard_pointer_clear (hp, 1);
650 mono_thread_info_suspend_unlock ();
654 Disabled by default for now.
655 To enable this we need mini to implement the callbacks by MonoThreadInfoRuntimeCallbacks
656 which means mono-context and setup_async_callback, and we need a mono-threads backend.
659 mono_thread_info_new_interrupt_enabled (void)
661 /*We need STW gc events to work correctly*/
662 #if defined (HAVE_BOEHM_GC) && !defined (USE_INCLUDED_LIBGC)
666 #if defined(HOST_WIN32)
669 #if defined (__i386__)
670 return !disable_new_interrupt;
676 * mono_thread_info_set_is_async_context:
678 * Set whenever the current thread is in an async context. Some runtime functions might behave
679 * differently while in an async context in order to be async safe.
682 mono_thread_info_set_is_async_context (gboolean async_context)
684 MonoThreadInfo *info = mono_thread_info_current ();
687 info->is_async_context = async_context;
691 mono_thread_info_is_async_context (void)
693 MonoThreadInfo *info = mono_thread_info_current ();
696 return info->is_async_context;
702 * mono_threads_create_thread:
704 * Create a new thread executing START with argument ARG. Store its id into OUT_TID.
705 * Returns: a windows or io-layer handle for the thread.
708 mono_threads_create_thread (LPTHREAD_START_ROUTINE start, gpointer arg, guint32 stack_size, guint32 creation_flags, MonoNativeThreadId *out_tid)
710 return mono_threads_core_create_thread (start, arg, stack_size, creation_flags, out_tid);
714 * mono_thread_info_get_stack_bounds:
716 * Return the address and size of the current threads stack. Return NULL as the
717 * stack address if the stack address cannot be determined.
720 mono_thread_info_get_stack_bounds (guint8 **staddr, size_t *stsize)
722 return mono_threads_core_get_stack_bounds (staddr, stsize);
726 mono_thread_info_yield (void)
728 return mono_threads_core_yield ();
732 mono_thread_info_tls_get (THREAD_INFO_TYPE *info, MonoTlsKey key)
734 return ((MonoThreadInfo*)info)->tls [key];
738 * mono_threads_info_tls_set:
740 * Set the TLS key to VALUE in the info structure. This can be used to obtain
741 * values of TLS variables for threads other than the current thread.
742 * This should only be used for infrequently changing TLS variables, and it should
743 * be paired with setting the real TLS variable since this provides no GC tracking.
746 mono_thread_info_tls_set (THREAD_INFO_TYPE *info, MonoTlsKey key, gpointer value)
748 ((MonoThreadInfo*)info)->tls [key] = value;