/* * mono-threads.c: Low-level threading * * Author: * Rodrigo Kumpera (kumpera@gmail.com) * * Copyright 2011 Novell, Inc (http://www.novell.com) * Copyright 2011 Xamarin, Inc (http://www.xamarin.com) */ #include #include #include #include #include #include #include #include #include #if defined(__MACH__) #include #endif #define THREADS_DEBUG(...) //#define THREADS_DEBUG(...) g_message(__VA_ARGS__) /* Mutex that makes sure only a single thread can be suspending others. Suspend is a very racy operation since it requires restarting until the target thread is not on an unsafe region. We could implement this using critical regions, but would be much much harder for an operation that is hardly performance critical. The GC has to acquire this lock before starting a STW to make sure a runtime suspend won't make it wronly see a thread in a safepoint when it is in fact not. */ static MonoSemType global_suspend_semaphore; static int thread_info_size; static MonoThreadInfoCallbacks threads_callbacks; static MonoThreadInfoRuntimeCallbacks runtime_callbacks; static MonoNativeTlsKey thread_info_key, small_id_key; static MonoLinkedListSet thread_list; static gboolean disable_new_interrupt = FALSE; static gboolean mono_threads_inited = FALSE; static void mono_threads_unregister_current_thread (MonoThreadInfo *info); static inline void mono_hazard_pointer_clear_all (MonoThreadHazardPointers *hp, int retain) { if (retain != 0) mono_hazard_pointer_clear (hp, 0); if (retain != 1) mono_hazard_pointer_clear (hp, 1); if (retain != 2) mono_hazard_pointer_clear (hp, 2); } /* If return non null Hazard Pointer 1 holds the return value. */ MonoThreadInfo* mono_thread_info_lookup (MonoNativeThreadId id) { MonoThreadHazardPointers *hp = mono_hazard_pointer_get (); if (!mono_lls_find (&thread_list, hp, (uintptr_t)id)) { mono_hazard_pointer_clear_all (hp, -1); return NULL; } mono_hazard_pointer_clear_all (hp, 1); return mono_hazard_pointer_get_val (hp, 1); } static gboolean mono_thread_info_insert (MonoThreadInfo *info) { MonoThreadHazardPointers *hp = mono_hazard_pointer_get (); if (!mono_lls_insert (&thread_list, hp, (MonoLinkedListSetNode*)info)) { mono_hazard_pointer_clear_all (hp, -1); return FALSE; } mono_hazard_pointer_clear_all (hp, -1); return TRUE; } static gboolean mono_thread_info_remove (MonoThreadInfo *info) { MonoThreadHazardPointers *hp = mono_hazard_pointer_get (); gboolean res; THREADS_DEBUG ("removing info %p\n", info); res = mono_lls_remove (&thread_list, hp, (MonoLinkedListSetNode*)info); mono_hazard_pointer_clear_all (hp, -1); return res; } static void free_thread_info (gpointer mem) { MonoThreadInfo *info = mem; MONO_SEM_DESTROY (&info->suspend_semaphore); MONO_SEM_DESTROY (&info->resume_semaphore); MONO_SEM_DESTROY (&info->finish_resume_semaphore); mono_threads_platform_free (info); g_free (info); } int mono_thread_info_register_small_id (void) { int small_id = mono_thread_small_id_alloc (); mono_native_tls_set_value (small_id_key, GUINT_TO_POINTER (small_id + 1)); return small_id; } static void* register_thread (MonoThreadInfo *info, gpointer baseptr) { int small_id = mono_thread_info_register_small_id (); gboolean result; mono_thread_info_set_tid (info, mono_native_thread_id_get ()); info->small_id = small_id; MONO_SEM_INIT (&info->suspend_semaphore, 1); MONO_SEM_INIT (&info->resume_semaphore, 0); MONO_SEM_INIT (&info->finish_resume_semaphore, 0); /*set TLS early so SMR works */ mono_native_tls_set_value (thread_info_key, info); THREADS_DEBUG ("registering info %p tid %p small id %x\n", info, mono_thread_info_get_tid (info), info->small_id); if (threads_callbacks.thread_register) { if (threads_callbacks.thread_register (info, baseptr) == NULL) { g_warning ("thread registation failed\n"); g_free (info); return NULL; } } mono_threads_platform_register (info); info->thread_state = STATE_RUNNING; mono_thread_info_suspend_lock (); /*If this fail it means a given thread has been registered twice, which doesn't make sense. */ result = mono_thread_info_insert (info); g_assert (result); mono_thread_info_suspend_unlock (); return info; } static void unregister_thread (void *arg) { MonoThreadInfo *info = arg; int small_id = info->small_id; g_assert (info); THREADS_DEBUG ("unregistering info %p\n", info); /* * TLS destruction order is not reliable so small_id might be cleaned up * before us. */ mono_native_tls_set_value (small_id_key, GUINT_TO_POINTER (info->small_id + 1)); info->thread_state = STATE_SHUTTING_DOWN; /* First perform the callback that requires no locks. This callback has the potential of taking other locks, so we do it before. After it completes, the thread remains functional. */ if (threads_callbacks.thread_detach) threads_callbacks.thread_detach (info); mono_thread_info_suspend_lock (); /* Now perform the callback that must be done under locks. This will render the thread useless and non-suspendable, so it must be done while holding the suspend lock to give no other thread chance to suspend it. */ if (threads_callbacks.thread_unregister) threads_callbacks.thread_unregister (info); mono_threads_unregister_current_thread (info); info->thread_state = STATE_DEAD; mono_thread_info_suspend_unlock (); /*now it's safe to free the thread info.*/ mono_thread_hazardous_free_or_queue (info, free_thread_info, TRUE, FALSE); mono_thread_small_id_free (small_id); } /** * Removes the current thread from the thread list. * This must be called from the thread unregister callback and nowhere else. * The current thread must be passed as TLS might have already been cleaned up. */ static void mono_threads_unregister_current_thread (MonoThreadInfo *info) { gboolean result; g_assert (mono_thread_info_get_tid (info) == mono_native_thread_id_get ()); result = mono_thread_info_remove (info); g_assert (result); } MonoThreadInfo* mono_thread_info_current (void) { MonoThreadInfo *info = (MonoThreadInfo*)mono_native_tls_get_value (thread_info_key); if (info) return info; info = mono_thread_info_lookup (mono_native_thread_id_get ()); /*info on HP1*/ /* We might be called during thread cleanup, but we cannot be called after cleanup as happened. The way to distinguish between before, during and after cleanup is the following: -If the TLS key is set, cleanup has not begun; -If the TLS key is clean, but the thread remains registered, cleanup is in progress; -If the thread is nowhere to be found, cleanup has finished. We cannot function after cleanup since there's no way to ensure what will happen. */ g_assert (info); /*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 */ mono_hazard_pointer_clear (mono_hazard_pointer_get (), 1); return info; } int mono_thread_info_get_small_id (void) { gpointer val = mono_native_tls_get_value (small_id_key); if (!val) return -1; return GPOINTER_TO_INT (val) - 1; } MonoLinkedListSet* mono_thread_info_list_head (void) { return &thread_list; } MonoThreadInfo* mono_thread_info_attach (void *baseptr) { MonoThreadInfo *info; if (!mono_threads_inited) { /* This can happen from DllMain(DLL_THREAD_ATTACH) on Windows, if a * thread is created before an embedding API user initialized Mono. */ THREADS_DEBUG ("mono_thread_info_attach called before mono_threads_init\n"); return NULL; } info = mono_native_tls_get_value (thread_info_key); if (!info) { info = g_malloc0 (thread_info_size); THREADS_DEBUG ("attaching %p\n", info); if (!register_thread (info, baseptr)) return NULL; } else if (threads_callbacks.thread_attach) { threads_callbacks.thread_attach (info); } return info; } void mono_thread_info_dettach (void) { MonoThreadInfo *info; if (!mono_threads_inited) { /* This can happen from DllMain(THREAD_DETACH) on Windows, if a thread * is created before an embedding API user initialized Mono. */ THREADS_DEBUG ("mono_thread_info_dettach called before mono_threads_init\n"); return; } info = mono_native_tls_get_value (thread_info_key); if (info) { THREADS_DEBUG ("detaching %p\n", info); unregister_thread (info); mono_native_tls_set_value (thread_info_key, NULL); } } void mono_threads_init (MonoThreadInfoCallbacks *callbacks, size_t info_size) { gboolean res; threads_callbacks = *callbacks; thread_info_size = info_size; #ifdef HOST_WIN32 res = mono_native_tls_alloc (&thread_info_key, NULL); #else res = mono_native_tls_alloc (&thread_info_key, unregister_thread); #endif g_assert (res); res = mono_native_tls_alloc (&small_id_key, NULL); g_assert (res); MONO_SEM_INIT (&global_suspend_semaphore, 1); mono_lls_init (&thread_list, NULL); mono_thread_smr_init (); mono_threads_init_platform (); #if defined(__MACH__) mono_mach_init (thread_info_key); #endif mono_threads_inited = TRUE; g_assert (sizeof (MonoNativeThreadId) <= sizeof (uintptr_t)); } void mono_threads_runtime_init (MonoThreadInfoRuntimeCallbacks *callbacks) { runtime_callbacks = *callbacks; } MonoThreadInfoCallbacks * mono_threads_get_callbacks (void) { return &threads_callbacks; } MonoThreadInfoRuntimeCallbacks * mono_threads_get_runtime_callbacks (void) { return &runtime_callbacks; } /* The return value is only valid until a matching mono_thread_info_resume is called */ static MonoThreadInfo* mono_thread_info_suspend_sync (MonoNativeThreadId tid, gboolean interrupt_kernel) { MonoThreadHazardPointers *hp = mono_hazard_pointer_get (); MonoThreadInfo *info = mono_thread_info_lookup (tid); /*info on HP1*/ if (!info) return NULL; MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore); /*thread is on the process of detaching*/ if (mono_thread_info_run_state (info) > STATE_RUNNING) { mono_hazard_pointer_clear (hp, 1); return NULL; } THREADS_DEBUG ("suspend %x IN COUNT %d\n", tid, info->suspend_count); if (info->suspend_count) { ++info->suspend_count; mono_hazard_pointer_clear (hp, 1); MONO_SEM_POST (&info->suspend_semaphore); return info; } if (!mono_threads_core_suspend (info)) { MONO_SEM_POST (&info->suspend_semaphore); mono_hazard_pointer_clear (hp, 1); return NULL; } if (interrupt_kernel) mono_threads_core_interrupt (info); ++info->suspend_count; info->thread_state |= STATE_SUSPENDED; MONO_SEM_POST (&info->suspend_semaphore); mono_hazard_pointer_clear (hp, 1); return info; } void mono_thread_info_self_suspend (void) { gboolean ret; MonoThreadInfo *info = mono_thread_info_current (); if (!info) return; MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore); THREADS_DEBUG ("self suspend IN COUNT %d\n", info->suspend_count); g_assert (info->suspend_count == 0); ++info->suspend_count; info->thread_state |= STATE_SELF_SUSPENDED; ret = mono_threads_get_runtime_callbacks ()->thread_state_init_from_sigctx (&info->suspend_state, NULL); g_assert (ret); MONO_SEM_POST (&info->suspend_semaphore); MONO_SEM_WAIT_UNITERRUPTIBLE (&info->resume_semaphore); g_assert (!info->async_target); /*FIXME this should happen normally for suspend. */ MONO_SEM_POST (&info->finish_resume_semaphore); } static gboolean mono_thread_info_resume_internal (MonoThreadInfo *info) { gboolean result; if (mono_thread_info_suspend_state (info) == STATE_SELF_SUSPENDED) { MONO_SEM_POST (&info->resume_semaphore); MONO_SEM_WAIT_UNITERRUPTIBLE (&info->finish_resume_semaphore); result = TRUE; } else { result = mono_threads_core_resume (info); } info->thread_state &= ~SUSPEND_STATE_MASK; return result; } gboolean mono_thread_info_resume (MonoNativeThreadId tid) { gboolean result = TRUE; MonoThreadHazardPointers *hp = mono_hazard_pointer_get (); MonoThreadInfo *info = mono_thread_info_lookup (tid); /*info on HP1*/ if (!info) return FALSE; MONO_SEM_WAIT_UNITERRUPTIBLE (&info->suspend_semaphore); THREADS_DEBUG ("resume %x IN COUNT %d\n",tid, info->suspend_count); if (info->suspend_count <= 0) { MONO_SEM_POST (&info->suspend_semaphore); mono_hazard_pointer_clear (hp, 1); return FALSE; } /* * The theory here is that if we manage to suspend the thread it means it did not * start cleanup since it take the same lock. */ g_assert (mono_thread_info_get_tid (info)); if (--info->suspend_count == 0) result = mono_thread_info_resume_internal (info); MONO_SEM_POST (&info->suspend_semaphore); mono_hazard_pointer_clear (hp, 1); mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, FALSE); return result; } void mono_thread_info_finish_suspend (void) { mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, FALSE); } /* FIXME fix cardtable WB to be out of line and check with the runtime if the target is not the WB trampoline. Another option is to encode wb ranges in MonoJitInfo, but that is somewhat hard. */ static gboolean is_thread_in_critical_region (MonoThreadInfo *info) { MonoMethod *method; MonoJitInfo *ji; if (info->inside_critical_region) return TRUE; /* The target thread might be shutting down and the domain might be null, which means no managed code left to run. */ if (!info->suspend_state.unwind_data [MONO_UNWIND_DATA_DOMAIN]) return FALSE; ji = mono_jit_info_table_find ( info->suspend_state.unwind_data [MONO_UNWIND_DATA_DOMAIN], MONO_CONTEXT_GET_IP (&info->suspend_state.ctx)); if (!ji) return FALSE; method = mono_jit_info_get_method (ji); return threads_callbacks.mono_method_is_critical (method); } /* WARNING: If we are trying to suspend a target that is on a critical region and running a syscall we risk looping forever if @interrupt_kernel is FALSE. So, be VERY carefull in calling this with @interrupt_kernel == FALSE. */ MonoThreadInfo* mono_thread_info_safe_suspend_sync (MonoNativeThreadId id, gboolean interrupt_kernel) { MonoThreadInfo *info = NULL; int sleep_duration = 0; /*FIXME: unify this with self-suspend*/ g_assert (id != mono_native_thread_id_get ()); mono_thread_info_suspend_lock (); for (;;) { if (!(info = mono_thread_info_suspend_sync (id, interrupt_kernel))) { g_warning ("failed to suspend thread %p, hopefully it is dead", (gpointer)id); mono_thread_info_suspend_unlock (); return NULL; } /*WARNING: We now are in interrupt context until we resume the thread. */ if (!is_thread_in_critical_region (info)) break; if (!mono_thread_info_resume (id)) { g_warning ("failed to result thread %p, hopefully it is dead", (gpointer)id); mono_thread_info_suspend_unlock (); return NULL; } THREADS_DEBUG ("restarted thread %p\n", (gpointer)id); if (!sleep_duration) { #ifdef HOST_WIN32 SwitchToThread (); #else sched_yield (); #endif } else { g_usleep (sleep_duration); } sleep_duration += 10; } mono_atomic_store_release (&mono_thread_info_current ()->inside_critical_region, TRUE); mono_thread_info_suspend_unlock (); return info; } /** Inject an assynchronous call into the target thread. The target thread must be suspended and only a single async call can be setup for a given suspend cycle. This async call must cause stack unwinding as the current implementation doesn't save enough state to resume execution of the top-of-stack function. It's an acceptable limitation since this is currently used only to deliver exceptions. */ void mono_thread_info_setup_async_call (MonoThreadInfo *info, void (*target_func)(void*), void *user_data) { g_assert (info->suspend_count); /*FIXME this is a bad assert, we probably should do proper locking and fail if one is already set*/ g_assert (!info->async_target); info->async_target = target_func; /* This is not GC tracked */ info->user_data = user_data; } /* The suspend lock is held during any suspend in progress. A GC that has safepoints must take this lock as part of its STW to make sure no unsafe pending suspend is in progress. */ void mono_thread_info_suspend_lock (void) { MONO_SEM_WAIT_UNITERRUPTIBLE (&global_suspend_semaphore); } void mono_thread_info_suspend_unlock (void) { MONO_SEM_POST (&global_suspend_semaphore); } void mono_thread_info_disable_new_interrupt (gboolean disable) { disable_new_interrupt = disable; } /* * This is a very specific function whose only purpose is to * break a given thread from socket syscalls. * * This only exists because linux won't fail a call to connect * if the underlying is closed. * * TODO We should cleanup and unify this with the other syscall abort * facility. */ void mono_thread_info_abort_socket_syscall_for_close (MonoNativeThreadId tid) { MonoThreadHazardPointers *hp; MonoThreadInfo *info; if (tid == mono_native_thread_id_get () || !mono_threads_core_needs_abort_syscall ()) return; hp = mono_hazard_pointer_get (); info = mono_thread_info_lookup (tid); /*info on HP1*/ if (!info) return; if (mono_thread_info_run_state (info) > STATE_RUNNING) { mono_hazard_pointer_clear (hp, 1); return; } mono_thread_info_suspend_lock (); mono_threads_core_abort_syscall (info); mono_hazard_pointer_clear (hp, 1); mono_thread_info_suspend_unlock (); } /* Disabled by default for now. To enable this we need mini to implement the callbacks by MonoThreadInfoRuntimeCallbacks which means mono-context and setup_async_callback, and we need a mono-threads backend. */ gboolean mono_thread_info_new_interrupt_enabled (void) { /*We need STW gc events to work correctly*/ #if defined (HAVE_BOEHM_GC) && !defined (USE_INCLUDED_LIBGC) return FALSE; #endif /*port not done*/ #if defined(HOST_WIN32) return FALSE; #endif #if defined (__i386__) return !disable_new_interrupt; #endif return FALSE; } /* * mono_thread_info_set_is_async_context: * * Set whenever the current thread is in an async context. Some runtime functions might behave * differently while in an async context in order to be async safe. */ void mono_thread_info_set_is_async_context (gboolean async_context) { MonoThreadInfo *info = mono_thread_info_current (); if (info) info->is_async_context = async_context; } gboolean mono_thread_info_is_async_context (void) { MonoThreadInfo *info = mono_thread_info_current (); if (info) return info->is_async_context; else return FALSE; } /* * mono_threads_create_thread: * * Create a new thread executing START with argument ARG. Store its id into OUT_TID. * Returns: a windows or io-layer handle for the thread. */ HANDLE mono_threads_create_thread (LPTHREAD_START_ROUTINE start, gpointer arg, guint32 stack_size, guint32 creation_flags, MonoNativeThreadId *out_tid) { HANDLE res; #ifdef HOST_WIN32 DWORD real_tid; res = mono_threads_CreateThread (NULL, stack_size, start, arg, creation_flags, &real_tid); if (out_tid) *out_tid = real_tid; #else gsize real_tid; res = CreateThread (NULL, stack_size, start, arg, creation_flags, &real_tid); if (out_tid) *out_tid = real_tid; #endif return res; }