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mono-threads.c
1543 lines (1283 loc) · 41.9 KB
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mono-threads.c
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/*
* 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 <config.h>
/* enable pthread extensions */
#ifdef TARGET_MACH
#define _DARWIN_C_SOURCE
#endif
#include <mono/utils/mono-compiler.h>
#include <mono/utils/mono-os-semaphore.h>
#include <mono/utils/mono-threads.h>
#include <mono/utils/mono-tls.h>
#include <mono/utils/hazard-pointer.h>
#include <mono/utils/mono-memory-model.h>
#include <mono/utils/mono-mmap.h>
#include <mono/utils/atomic.h>
#include <mono/utils/mono-time.h>
#include <mono/utils/mono-lazy-init.h>
#include <mono/utils/mono-coop-mutex.h>
#include <mono/utils/mono-coop-semaphore.h>
#include <errno.h>
#if defined(__MACH__)
#include <mono/utils/mach-support.h>
#endif
/*
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 MonoCoopSem global_suspend_semaphore;
static size_t thread_info_size;
static MonoThreadInfoCallbacks threads_callbacks;
static MonoThreadInfoRuntimeCallbacks runtime_callbacks;
static MonoNativeTlsKey thread_info_key, thread_exited_key;
#ifdef HAVE_KW_THREAD
static __thread guint32 tls_small_id MONO_TLS_FAST;
#else
static MonoNativeTlsKey small_id_key;
#endif
static MonoLinkedListSet thread_list;
static gboolean mono_threads_inited = FALSE;
static MonoSemType suspend_semaphore;
static size_t pending_suspends;
static gboolean unified_suspend_enabled;
#define mono_thread_info_run_state(info) (((MonoThreadInfo*)info)->thread_state & THREAD_STATE_MASK)
/*warn at 50 ms*/
#define SLEEP_DURATION_BEFORE_WARNING (10)
/*abort at 1 sec*/
#define SLEEP_DURATION_BEFORE_ABORT 200
static int suspend_posts, resume_posts, abort_posts, waits_done, pending_ops;
void
mono_threads_notify_initiator_of_abort (MonoThreadInfo* info)
{
THREADS_SUSPEND_DEBUG ("[INITIATOR-NOTIFY-ABORT] %p\n", mono_thread_info_get_tid (info));
InterlockedIncrement (&abort_posts);
mono_os_sem_post (&suspend_semaphore);
}
void
mono_threads_notify_initiator_of_suspend (MonoThreadInfo* info)
{
THREADS_SUSPEND_DEBUG ("[INITIATOR-NOTIFY-SUSPEND] %p\n", mono_thread_info_get_tid (info));
InterlockedIncrement (&suspend_posts);
mono_os_sem_post (&suspend_semaphore);
}
void
mono_threads_notify_initiator_of_resume (MonoThreadInfo* info)
{
THREADS_SUSPEND_DEBUG ("[INITIATOR-NOTIFY-RESUME] %p\n", mono_thread_info_get_tid (info));
InterlockedIncrement (&resume_posts);
mono_os_sem_post (&suspend_semaphore);
}
static gboolean
begin_async_suspend (MonoThreadInfo *info, gboolean interrupt_kernel)
{
if (mono_threads_is_coop_enabled ()) {
/* There's nothing else to do after we async request the thread to suspend */
mono_threads_add_to_pending_operation_set (info);
return TRUE;
}
return mono_threads_core_begin_async_suspend (info, interrupt_kernel);
}
static gboolean
check_async_suspend (MonoThreadInfo *info)
{
if (mono_threads_is_coop_enabled ()) {
/* Async suspend can't async fail on coop */
return TRUE;
}
return mono_threads_core_check_suspend_result (info);
}
static void
resume_async_suspended (MonoThreadInfo *info)
{
if (mono_threads_is_coop_enabled ())
g_assert_not_reached ();
g_assert (mono_threads_core_begin_async_resume (info));
}
static void
resume_self_suspended (MonoThreadInfo* info)
{
THREADS_SUSPEND_DEBUG ("**BEGIN self-resume %p\n", mono_thread_info_get_tid (info));
mono_os_sem_post (&info->resume_semaphore);
}
void
mono_thread_info_wait_for_resume (MonoThreadInfo* info)
{
int res;
THREADS_SUSPEND_DEBUG ("**WAIT self-resume %p\n", mono_thread_info_get_tid (info));
res = mono_os_sem_wait (&info->resume_semaphore, MONO_SEM_FLAGS_NONE);
g_assert (res != -1);
}
static void
resume_blocking_suspended (MonoThreadInfo* info)
{
THREADS_SUSPEND_DEBUG ("**BEGIN blocking-resume %p\n", mono_thread_info_get_tid (info));
mono_os_sem_post (&info->resume_semaphore);
}
void
mono_threads_add_to_pending_operation_set (MonoThreadInfo* info)
{
THREADS_SUSPEND_DEBUG ("added %p to pending suspend\n", mono_thread_info_get_tid (info));
++pending_suspends;
InterlockedIncrement (&pending_ops);
}
void
mono_threads_begin_global_suspend (void)
{
size_t ps = pending_suspends;
if (G_UNLIKELY (ps != 0))
g_error ("pending_suspends = %d, but must be 0", ps);
THREADS_SUSPEND_DEBUG ("------ BEGIN GLOBAL OP sp %d rp %d ap %d wd %d po %d (sp + rp + ap == wd) (wd == po)\n", suspend_posts, resume_posts,
abort_posts, waits_done, pending_ops);
g_assert ((suspend_posts + resume_posts + abort_posts) == waits_done);
mono_threads_coop_begin_global_suspend ();
}
void
mono_threads_end_global_suspend (void)
{
size_t ps = pending_suspends;
if (G_UNLIKELY (ps != 0))
g_error ("pending_suspends = %d, but must be 0", ps);
THREADS_SUSPEND_DEBUG ("------ END GLOBAL OP sp %d rp %d ap %d wd %d po %d\n", suspend_posts, resume_posts,
abort_posts, waits_done, pending_ops);
g_assert ((suspend_posts + resume_posts + abort_posts) == waits_done);
mono_threads_coop_end_global_suspend ();
}
static void
dump_threads (void)
{
MonoThreadInfo *info;
MonoThreadInfo *cur = mono_thread_info_current ();
MOSTLY_ASYNC_SAFE_PRINTF ("STATE CUE CARD: (? means a positive number, usually 1 or 2, * means any number)\n");
MOSTLY_ASYNC_SAFE_PRINTF ("\t0x0\t- starting (GOOD, unless the thread is running managed code)\n");
MOSTLY_ASYNC_SAFE_PRINTF ("\t0x1\t- running (BAD, unless it's the gc thread)\n");
MOSTLY_ASYNC_SAFE_PRINTF ("\t0x2\t- detached (GOOD, unless the thread is running managed code)\n");
MOSTLY_ASYNC_SAFE_PRINTF ("\t0x?03\t- async suspended (GOOD)\n");
MOSTLY_ASYNC_SAFE_PRINTF ("\t0x?04\t- self suspended (GOOD)\n");
MOSTLY_ASYNC_SAFE_PRINTF ("\t0x?05\t- async suspend requested (BAD)\n");
MOSTLY_ASYNC_SAFE_PRINTF ("\t0x?06\t- self suspend requested (BAD)\n");
MOSTLY_ASYNC_SAFE_PRINTF ("\t0x*07\t- blocking (GOOD)\n");
MOSTLY_ASYNC_SAFE_PRINTF ("\t0x?08\t- blocking with pending suspend (GOOD)\n");
FOREACH_THREAD_SAFE (info) {
#ifdef TARGET_MACH
char thread_name [256] = { 0 };
pthread_getname_np (mono_thread_info_get_tid (info), thread_name, 255);
MOSTLY_ASYNC_SAFE_PRINTF ("--thread %p id %p [%p] (%s) state %x %s\n", info, (void *) mono_thread_info_get_tid (info), (void*)(size_t)info->native_handle, thread_name, info->thread_state, info == cur ? "GC INITIATOR" : "" );
#else
MOSTLY_ASYNC_SAFE_PRINTF ("--thread %p id %p [%p] state %x %s\n", info, (void *) mono_thread_info_get_tid (info), (void*)(size_t)info->native_handle, info->thread_state, info == cur ? "GC INITIATOR" : "" );
#endif
} END_FOREACH_THREAD_SAFE
}
gboolean
mono_threads_wait_pending_operations (void)
{
int i;
int c = pending_suspends;
/* Wait threads to park */
THREADS_SUSPEND_DEBUG ("[INITIATOR-WAIT-COUNT] %d\n", c);
if (pending_suspends) {
MonoStopwatch suspension_time;
mono_stopwatch_start (&suspension_time);
for (i = 0; i < pending_suspends; ++i) {
THREADS_SUSPEND_DEBUG ("[INITIATOR-WAIT-WAITING]\n");
InterlockedIncrement (&waits_done);
if (!mono_os_sem_timedwait (&suspend_semaphore, SLEEP_DURATION_BEFORE_ABORT, MONO_SEM_FLAGS_NONE))
continue;
mono_stopwatch_stop (&suspension_time);
dump_threads ();
MOSTLY_ASYNC_SAFE_PRINTF ("WAITING for %d threads, got %d suspended\n", (int)pending_suspends, i);
g_error ("suspend_thread suspend took %d ms, which is more than the allowed %d ms", (int)mono_stopwatch_elapsed_ms (&suspension_time), SLEEP_DURATION_BEFORE_ABORT);
}
mono_stopwatch_stop (&suspension_time);
THREADS_SUSPEND_DEBUG ("Suspending %d threads took %d ms.\n", (int)pending_suspends, (int)mono_stopwatch_elapsed_ms (&suspension_time));
}
pending_suspends = 0;
return c > 0;
}
//Thread initialization code
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 (MonoThreadInfo *) 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 = (MonoThreadInfo *) mem;
mono_os_sem_destroy (&info->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 ();
#ifdef HAVE_KW_THREAD
tls_small_id = small_id;
#else
mono_native_tls_set_value (small_id_key, GUINT_TO_POINTER (small_id + 1));
#endif
return small_id;
}
static void*
register_thread (MonoThreadInfo *info, gpointer baseptr)
{
size_t stsize = 0;
guint8 *staddr = NULL;
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_os_sem_init (&info->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_thread_info_get_stack_bounds (&staddr, &stsize);
g_assert (staddr);
g_assert (stsize);
info->stack_start_limit = staddr;
info->stack_end = staddr + stsize;
info->stackdata = g_byte_array_new ();
mono_threads_platform_register (info);
/*
Transition it before taking any locks or publishing itself to reduce the chance
of others witnessing a detached thread.
We can reasonably expect that until this thread gets published, no other thread will
try to manipulate it.
*/
mono_threads_transition_attach (info);
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 = (MonoThreadInfo *) arg;
int small_id = info->small_id;
g_assert (info);
THREADS_DEBUG ("unregistering info %p\n", info);
mono_native_tls_set_value (thread_exited_key, GUINT_TO_POINTER (1));
mono_threads_core_unregister (info);
/*
* TLS destruction order is not reliable so small_id might be cleaned up
* before us.
*/
#ifndef HAVE_KW_THREAD
mono_native_tls_set_value (small_id_key, GUINT_TO_POINTER (info->small_id + 1));
#endif
/*
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);
mono_threads_transition_detach (info);
mono_thread_info_suspend_unlock ();
g_byte_array_free (info->stackdata, /*free_segment=*/TRUE);
/*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);
}
static void
thread_exited_dtor (void *arg)
{
#if defined(__MACH__)
/*
* Since we use pthread dtors to clean up thread data, if a thread
* is attached to the runtime by another pthread dtor after our dtor
* has ran, it will never be detached, leading to various problems
* since the thread ids etc. will be reused while they are still in
* the threads hashtables etc.
* Dtors are called in a loop until all user tls entries are 0,
* but the loop has a maximum count (4), so if we set the tls
* variable every time, it will remain set when system tls dtors
* are ran. This allows mono_thread_info_is_exiting () to detect
* whenever the thread is exiting, even if it is executed from a
* system tls dtor (i.e. obj-c dealloc methods).
*/
mono_native_tls_set_value (thread_exited_key, GUINT_TO_POINTER (1));
#endif
}
/**
* 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_unchecked (void)
{
return mono_threads_inited ? (MonoThreadInfo*)mono_native_tls_get_value (thread_info_key) : NULL;
}
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)
{
#ifdef HAVE_KW_THREAD
return tls_small_id;
#else
gpointer val = mono_native_tls_get_value (small_id_key);
if (!val)
return -1;
return GPOINTER_TO_INT (val) - 1;
#endif
}
MonoLinkedListSet*
mono_thread_info_list_head (void)
{
return &thread_list;
}
/**
* mono_threads_attach_tools_thread
*
* Attach the current thread as a tool thread. DON'T USE THIS FUNCTION WITHOUT READING ALL DISCLAIMERS.
*
* A tools thread is a very special kind of thread that needs access to core runtime facilities but should
* not be counted as a regular thread for high order facilities such as executing managed code or accessing
* the managed heap.
*
* This is intended only to tools such as a profiler than needs to be able to use our lock-free support when
* doing things like resolving backtraces in their background processing thread.
*/
void
mono_threads_attach_tools_thread (void)
{
int dummy = 0;
MonoThreadInfo *info;
/* Must only be called once */
g_assert (!mono_native_tls_get_value (thread_info_key));
while (!mono_threads_inited) {
mono_thread_info_usleep (10);
}
info = mono_thread_info_attach (&dummy);
g_assert (info);
info->tools_thread = TRUE;
}
MonoThreadInfo*
mono_thread_info_attach (void *baseptr)
{
MonoThreadInfo *info;
if (!mono_threads_inited)
{
#ifdef HOST_WIN32
/* 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;
#else
g_assert (mono_threads_inited);
#endif
}
info = (MonoThreadInfo *) mono_native_tls_get_value (thread_info_key);
if (!info) {
info = (MonoThreadInfo *) 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_detach (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_detach called before mono_threads_init\n");
return;
}
info = (MonoThreadInfo *) 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);
}
}
/*
* mono_thread_info_is_exiting:
*
* Return whenever the current thread is exiting, i.e. it is running pthread
* dtors.
*/
gboolean
mono_thread_info_is_exiting (void)
{
#if defined(__MACH__)
if (mono_native_tls_get_value (thread_exited_key) == GUINT_TO_POINTER (1))
return TRUE;
#endif
return FALSE;
}
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);
res = mono_native_tls_alloc (&thread_exited_key, NULL);
#else
res = mono_native_tls_alloc (&thread_info_key, (void *) unregister_thread);
res = mono_native_tls_alloc (&thread_exited_key, (void *) thread_exited_dtor);
#endif
g_assert (res);
#ifndef HAVE_KW_THREAD
res = mono_native_tls_alloc (&small_id_key, NULL);
#endif
g_assert (res);
unified_suspend_enabled = g_getenv ("MONO_ENABLE_UNIFIED_SUSPEND") != NULL || mono_threads_is_coop_enabled ();
mono_coop_sem_init (&global_suspend_semaphore, 1);
mono_os_sem_init (&suspend_semaphore, 0);
mono_lls_init (&thread_list, NULL);
mono_thread_smr_init ();
mono_threads_init_platform ();
mono_threads_init_coop ();
mono_threads_init_abort_syscall ();
#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;
}
MonoThreadInfoRuntimeCallbacks *
mono_threads_get_runtime_callbacks (void)
{
return &runtime_callbacks;
}
/*
Signal that the current thread wants to be suspended.
This function can be called without holding the suspend lock held.
To finish suspending, call mono_suspend_check.
*/
void
mono_thread_info_begin_self_suspend (void)
{
MonoThreadInfo *info = mono_thread_info_current_unchecked ();
if (!info)
return;
THREADS_SUSPEND_DEBUG ("BEGIN SELF SUSPEND OF %p\n", info);
mono_threads_transition_request_self_suspension (info);
}
void
mono_thread_info_end_self_suspend (void)
{
MonoThreadInfo *info;
info = mono_thread_info_current ();
if (!info)
return;
THREADS_SUSPEND_DEBUG ("FINISH SELF SUSPEND OF %p\n", info);
mono_threads_get_runtime_callbacks ()->thread_state_init (&info->thread_saved_state [SELF_SUSPEND_STATE_INDEX]);
/* commit the saved state and notify others if needed */
switch (mono_threads_transition_state_poll (info)) {
case SelfSuspendResumed:
return;
case SelfSuspendWait:
mono_thread_info_wait_for_resume (info);
break;
case SelfSuspendNotifyAndWait:
mono_threads_notify_initiator_of_suspend (info);
mono_thread_info_wait_for_resume (info);
mono_threads_notify_initiator_of_resume (info);
break;
}
}
static gboolean
mono_thread_info_core_resume (MonoThreadInfo *info)
{
gboolean res = FALSE;
if (info->create_suspended) {
MonoNativeThreadId tid = mono_thread_info_get_tid (info);
/* 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 */
info->create_suspended = FALSE;
mono_threads_core_resume_created (info, tid);
return TRUE;
}
switch (mono_threads_transition_request_resume (info)) {
case ResumeError:
res = FALSE;
break;
case ResumeOk:
res = TRUE;
break;
case ResumeInitSelfResume:
resume_self_suspended (info);
res = TRUE;
break;
case ResumeInitAsyncResume:
resume_async_suspended (info);
res = TRUE;
break;
case ResumeInitBlockingResume:
resume_blocking_suspended (info);
res = TRUE;
break;
}
return res;
}
gboolean
mono_thread_info_resume (MonoNativeThreadId tid)
{
gboolean result; /* don't initialize it so the compiler can catch unitilized paths. */
MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
MonoThreadInfo *info;
THREADS_SUSPEND_DEBUG ("RESUMING tid %p\n", (void*)tid);
mono_thread_info_suspend_lock ();
info = mono_thread_info_lookup (tid); /*info on HP1*/
if (!info) {
result = FALSE;
goto cleanup;
}
result = mono_thread_info_core_resume (info);
//Wait for the pending resume to finish
mono_threads_wait_pending_operations ();
cleanup:
mono_thread_info_suspend_unlock ();
mono_hazard_pointer_clear (hp, 1);
return result;
}
gboolean
mono_thread_info_begin_suspend (MonoThreadInfo *info)
{
switch (mono_threads_transition_request_async_suspension (info)) {
case AsyncSuspendAlreadySuspended:
case AsyncSuspendBlocking:
return TRUE;
case AsyncSuspendWait:
mono_threads_add_to_pending_operation_set (info);
return TRUE;
case AsyncSuspendInitSuspend:
return begin_async_suspend (info, FALSE);
default:
g_assert_not_reached ();
}
}
gboolean
mono_thread_info_begin_resume (MonoThreadInfo *info)
{
return mono_thread_info_core_resume (info);
}
gboolean
mono_thread_info_check_suspend_result (MonoThreadInfo *info)
{
return check_async_suspend (info);
}
/*
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;
gpointer stack_start;
MonoThreadUnwindState *state;
/* Are we inside a system critical region? */
if (info->inside_critical_region)
return TRUE;
/* Are we inside a GC critical region? */
if (threads_callbacks.mono_thread_in_critical_region && threads_callbacks.mono_thread_in_critical_region (info)) {
return TRUE;
}
/* The target thread might be shutting down and the domain might be null, which means no managed code left to run. */
state = mono_thread_info_get_suspend_state (info);
if (!state->unwind_data [MONO_UNWIND_DATA_DOMAIN])
return FALSE;
stack_start = MONO_CONTEXT_GET_SP (&state->ctx);
/* altstack signal handler, sgen can't handle them, so we treat them as critical */
if (stack_start < info->stack_start_limit || stack_start >= info->stack_end)
return TRUE;
ji = mono_jit_info_table_find (
(MonoDomain *) state->unwind_data [MONO_UNWIND_DATA_DOMAIN],
(char *) MONO_CONTEXT_GET_IP (&state->ctx));
if (!ji)
return FALSE;
method = mono_jit_info_get_method (ji);
return threads_callbacks.mono_method_is_critical (method);
}
gboolean
mono_thread_info_in_critical_location (MonoThreadInfo *info)
{
return is_thread_in_critical_region (info);
}
/*
The return value is only valid until a matching mono_thread_info_resume is called
*/
static MonoThreadInfo*
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;
switch (mono_threads_transition_request_async_suspension (info)) {
case AsyncSuspendAlreadySuspended:
mono_hazard_pointer_clear (hp, 1); //XXX this is questionable we got to clean the suspend/resume nonsense of critical sections
return info;
case AsyncSuspendWait:
mono_threads_add_to_pending_operation_set (info);
break;
case AsyncSuspendInitSuspend:
if (!begin_async_suspend (info, interrupt_kernel)) {
mono_hazard_pointer_clear (hp, 1);
return NULL;
}
break;
case AsyncSuspendBlocking:
if (interrupt_kernel)
mono_threads_core_abort_syscall (info);
break;
default:
g_assert_not_reached ();
}
//Wait for the pending suspend to finish
mono_threads_wait_pending_operations ();
if (!check_async_suspend (info)) {
mono_hazard_pointer_clear (hp, 1);
return NULL;
}
return info;
}
static MonoThreadInfo*
suspend_sync_nolock (MonoNativeThreadId id, gboolean interrupt_kernel)
{
MonoThreadInfo *info = NULL;
int sleep_duration = 0;
for (;;) {
if (!(info = suspend_sync (id, interrupt_kernel))) {
mono_hazard_pointer_clear (mono_hazard_pointer_get (), 1);
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_core_resume (info)) {
mono_hazard_pointer_clear (mono_hazard_pointer_get (), 1);
return NULL;
}
THREADS_SUSPEND_DEBUG ("RESTARTED thread tid %p\n", (void*)id);
/* Wait for the pending resume to finish */
mono_threads_wait_pending_operations ();
if (sleep_duration == 0)
mono_thread_info_yield ();
else
g_usleep (sleep_duration);
sleep_duration += 10;
}
return info;
}
void
mono_thread_info_safe_suspend_and_run (MonoNativeThreadId id, gboolean interrupt_kernel, MonoSuspendThreadCallback callback, gpointer user_data)
{
int result;
MonoThreadInfo *info = NULL;
MonoThreadHazardPointers *hp = mono_hazard_pointer_get ();
THREADS_SUSPEND_DEBUG ("SUSPENDING tid %p\n", (void*)id);
/*FIXME: unify this with self-suspend*/
g_assert (id != mono_native_thread_id_get ());
/* This can block during stw */
mono_thread_info_suspend_lock ();
mono_threads_begin_global_suspend ();
info = suspend_sync_nolock (id, interrupt_kernel);
if (!info)
goto done;
switch (result = callback (info, user_data)) {
case MonoResumeThread:
mono_hazard_pointer_set (hp, 1, info);
mono_thread_info_core_resume (info);
mono_threads_wait_pending_operations ();
break;
case KeepSuspended:
break;
default:
g_error ("Invalid suspend_and_run callback return value %d", result);
}
done:
mono_hazard_pointer_clear (hp, 1);
mono_threads_end_global_suspend ();
mono_thread_info_suspend_unlock ();
}
/**
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)
{
/* An async call can only be setup on an async suspended thread */
g_assert (mono_thread_info_run_state (info) == STATE_ASYNC_SUSPENDED);
/*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)
{
int res = mono_coop_sem_wait (&global_suspend_semaphore, MONO_SEM_FLAGS_NONE);
g_assert (res != -1);
}
void
mono_thread_info_suspend_unlock (void)
{
mono_coop_sem_post (&global_suspend_semaphore);