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pthread_stop_world.c
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/*
* Copyright (c) 1994 by Xerox Corporation. All rights reserved.
* Copyright (c) 1996 by Silicon Graphics. All rights reserved.
* Copyright (c) 1998 by Fergus Henderson. All rights reserved.
* Copyright (c) 2000-2009 by Hewlett-Packard Development Company.
* All rights reserved.
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to use or copy this program
* for any purpose, provided the above notices are retained on all copies.
* Permission to modify the code and to distribute modified code is granted,
* provided the above notices are retained, and a notice that the code was
* modified is included with the above copyright notice.
*/
#include "private/pthread_support.h"
#if defined(GC_PTHREADS) && !defined(GC_WIN32_THREADS) && \
!defined(GC_DARWIN_THREADS) && !defined(SN_TARGET_ORBIS) \
&& !defined(SN_TARGET_PSP2)
#ifdef NACL
# include <unistd.h>
# include <sys/time.h>
STATIC int GC_nacl_num_gc_threads = 0;
STATIC __thread int GC_nacl_thread_idx = -1;
STATIC volatile int GC_nacl_park_threads_now = 0;
STATIC volatile pthread_t GC_nacl_thread_parker = -1;
GC_INNER __thread GC_thread GC_nacl_gc_thread_self = NULL;
volatile int GC_nacl_thread_parked[MAX_NACL_GC_THREADS];
int GC_nacl_thread_used[MAX_NACL_GC_THREADS];
#elif defined(GC_OPENBSD_UTHREADS)
# include <pthread_np.h>
#else /* !GC_OPENBSD_UTHREADS && !NACL */
#include <signal.h>
#include <semaphore.h>
#include <errno.h>
#include <time.h> /* for nanosleep() */
#include <unistd.h>
#include "private/gc_atomic_ops.h"
#if (!defined(AO_HAVE_load_acquire) || !defined(AO_HAVE_store_release)) \
&& !defined(CPPCHECK)
# error AO_load_acquire and/or AO_store_release are missing;
# error please define AO_REQUIRE_CAS manually
#endif
/* It's safe to call original pthread_sigmask() here. */
#undef pthread_sigmask
#ifdef GC_ENABLE_SUSPEND_THREAD
static void *GC_CALLBACK suspend_self_inner(void *client_data);
#endif
#ifdef DEBUG_THREADS
# ifndef NSIG
# if defined(MAXSIG)
# define NSIG (MAXSIG+1)
# elif defined(_NSIG)
# define NSIG _NSIG
# elif defined(__SIGRTMAX)
# define NSIG (__SIGRTMAX+1)
# else
# error define NSIG
# endif
# endif /* NSIG */
void GC_print_sig_mask(void)
{
sigset_t blocked;
int i;
if (pthread_sigmask(SIG_BLOCK, NULL, &blocked) != 0)
ABORT("pthread_sigmask failed");
for (i = 1; i < NSIG; i++) {
if (sigismember(&blocked, i))
GC_printf("Signal blocked: %d\n", i);
}
}
#endif /* DEBUG_THREADS */
/* Remove the signals that we want to allow in thread stopping */
/* handler from a set. */
STATIC void GC_remove_allowed_signals(sigset_t *set)
{
if (sigdelset(set, SIGINT) != 0
|| sigdelset(set, SIGQUIT) != 0
|| sigdelset(set, SIGABRT) != 0
|| sigdelset(set, SIGTERM) != 0) {
ABORT("sigdelset failed");
}
# ifdef MPROTECT_VDB
/* Handlers write to the thread structure, which is in the heap, */
/* and hence can trigger a protection fault. */
if (sigdelset(set, SIGSEGV) != 0
# ifdef HAVE_SIGBUS
|| sigdelset(set, SIGBUS) != 0
# endif
) {
ABORT("sigdelset failed");
}
# endif
}
static sigset_t suspend_handler_mask;
STATIC volatile AO_t GC_stop_count = 0;
/* Incremented at the beginning of GC_stop_world. */
STATIC volatile AO_t GC_world_is_stopped = FALSE;
/* FALSE ==> it is safe for threads to restart, */
/* i.e. they will see another suspend signal */
/* before they are expected to stop (unless */
/* they have stopped voluntarily). */
#if defined(GC_OSF1_THREADS) || defined(THREAD_SANITIZER)
STATIC GC_bool GC_retry_signals = TRUE;
#else
STATIC GC_bool GC_retry_signals = FALSE;
#endif
/*
* We use signals to stop threads during GC.
*
* Suspended threads wait in signal handler for SIG_THR_RESTART.
* That's more portable than semaphores or condition variables.
* (We do use sem_post from a signal handler, but that should be portable.)
*
* The thread suspension signal SIG_SUSPEND is now defined in gc_priv.h.
* Note that we can't just stop a thread; we need it to save its stack
* pointer(s) and acknowledge.
*/
#ifndef SIG_THR_RESTART
# if defined(GC_HPUX_THREADS) || defined(GC_OSF1_THREADS) \
|| defined(GC_NETBSD_THREADS) || defined(GC_USESIGRT_SIGNALS)
# if defined(_SIGRTMIN) && !defined(CPPCHECK)
# define SIG_THR_RESTART _SIGRTMIN + 5
# else
# define SIG_THR_RESTART SIGRTMIN + 5
# endif
# else
# define SIG_THR_RESTART SIGXCPU
# endif
#endif
#define SIGNAL_UNSET (-1)
/* Since SIG_SUSPEND and/or SIG_THR_RESTART could represent */
/* a non-constant expression (e.g., in case of SIGRTMIN), */
/* actual signal numbers are determined by GC_stop_init() */
/* unless manually set (before GC initialization). */
STATIC int GC_sig_suspend = SIGNAL_UNSET;
STATIC int GC_sig_thr_restart = SIGNAL_UNSET;
GC_API void GC_CALL GC_set_suspend_signal(int sig)
{
if (GC_is_initialized) return;
GC_sig_suspend = sig;
}
GC_API void GC_CALL GC_set_thr_restart_signal(int sig)
{
if (GC_is_initialized) return;
GC_sig_thr_restart = sig;
}
GC_API int GC_CALL GC_get_suspend_signal(void)
{
return GC_sig_suspend != SIGNAL_UNSET ? GC_sig_suspend : SIG_SUSPEND;
}
GC_API int GC_CALL GC_get_thr_restart_signal(void)
{
return GC_sig_thr_restart != SIGNAL_UNSET
? GC_sig_thr_restart : SIG_THR_RESTART;
}
#ifdef GC_EXPLICIT_SIGNALS_UNBLOCK
/* Some targets (e.g., Solaris) might require this to be called when */
/* doing thread registering from the thread destructor. */
GC_INNER void GC_unblock_gc_signals(void)
{
sigset_t set;
sigemptyset(&set);
GC_ASSERT(GC_sig_suspend != SIGNAL_UNSET);
GC_ASSERT(GC_sig_thr_restart != SIGNAL_UNSET);
sigaddset(&set, GC_sig_suspend);
sigaddset(&set, GC_sig_thr_restart);
if (pthread_sigmask(SIG_UNBLOCK, &set, NULL) != 0)
ABORT("pthread_sigmask failed");
}
#endif /* GC_EXPLICIT_SIGNALS_UNBLOCK */
STATIC sem_t GC_suspend_ack_sem;
#ifdef GC_NETBSD_THREADS_WORKAROUND
/* In case of it is necessary to wait until threads have restarted. */
STATIC sem_t GC_restart_ack_sem;
#endif
STATIC void GC_suspend_handler_inner(ptr_t dummy, void *context);
#ifndef NO_SA_SIGACTION
STATIC void GC_suspend_handler(int sig, siginfo_t * info GC_ATTR_UNUSED,
void * context GC_ATTR_UNUSED)
#else
STATIC void GC_suspend_handler(int sig)
#endif
{
int old_errno = errno;
if (sig != GC_sig_suspend) {
# if defined(GC_FREEBSD_THREADS)
/* Workaround "deferred signal handling" bug in FreeBSD 9.2. */
if (0 == sig) return;
# endif
ABORT("Bad signal in suspend_handler");
}
# if defined(IA64) || defined(HP_PA) || defined(M68K)
GC_with_callee_saves_pushed(GC_suspend_handler_inner, NULL);
# else
/* We believe that in all other cases the full context is already */
/* in the signal handler frame. */
{
# ifdef NO_SA_SIGACTION
void *context = 0;
# endif
GC_suspend_handler_inner(NULL, context);
}
# endif
errno = old_errno;
}
/* The lookup here is safe, since this is done on behalf */
/* of a thread which holds the allocation lock in order */
/* to stop the world. Thus concurrent modification of the */
/* data structure is impossible. Unfortunately, we have to */
/* instruct TSan that the lookup is safe. */
#ifdef THREAD_SANITIZER
/* The implementation of the function is the same as that of */
/* GC_lookup_thread except for the attribute added here. */
GC_ATTR_NO_SANITIZE_THREAD
static GC_thread GC_lookup_thread_async(pthread_t id)
{
GC_thread p = GC_threads[THREAD_TABLE_INDEX(id)];
while (p != NULL && !THREAD_EQUAL(p->id, id))
p = p->next;
return p;
}
#else
# define GC_lookup_thread_async GC_lookup_thread
#endif
GC_INLINE void GC_store_stack_ptr(GC_thread me)
{
/* There is no data race between the suspend handler (storing */
/* stack_ptr) and GC_push_all_stacks (fetching stack_ptr) because */
/* GC_push_all_stacks is executed after GC_stop_world exits and the */
/* latter runs sem_wait repeatedly waiting for all the suspended */
/* threads to call sem_post. Nonetheless, stack_ptr is stored (here) */
/* and fetched (by GC_push_all_stacks) using the atomic primitives to */
/* avoid the related TSan warning. */
# ifdef SPARC
AO_store((volatile AO_t *)&me->stop_info.stack_ptr,
(AO_t)GC_save_regs_in_stack());
# else
# ifdef IA64
me -> backing_store_ptr = GC_save_regs_in_stack();
# endif
AO_store((volatile AO_t *)&me->stop_info.stack_ptr, (AO_t)GC_approx_sp());
# endif
}
STATIC void GC_suspend_handler_inner(ptr_t dummy GC_ATTR_UNUSED,
void * context GC_ATTR_UNUSED)
{
pthread_t self = pthread_self();
GC_thread me;
IF_CANCEL(int cancel_state;)
AO_t my_stop_count = AO_load_acquire(&GC_stop_count);
/* After the barrier, this thread should see */
/* the actual content of GC_threads. */
DISABLE_CANCEL(cancel_state);
/* pthread_setcancelstate is not defined to be async-signal-safe. */
/* But the glibc version appears to be in the absence of */
/* asynchronous cancellation. And since this signal handler */
/* to block on sigsuspend, which is both async-signal-safe */
/* and a cancellation point, there seems to be no obvious way */
/* out of it. In fact, it looks to me like an async-signal-safe */
/* cancellation point is inherently a problem, unless there is */
/* some way to disable cancellation in the handler. */
# ifdef DEBUG_THREADS
GC_log_printf("Suspending %p\n", (void *)self);
# endif
me = GC_lookup_thread_async(self);
# ifdef GC_ENABLE_SUSPEND_THREAD
if (AO_load(&me->suspended_ext)) {
GC_store_stack_ptr(me);
sem_post(&GC_suspend_ack_sem);
suspend_self_inner(me);
# ifdef DEBUG_THREADS
GC_log_printf("Continuing %p on GC_resume_thread\n", (void *)self);
# endif
RESTORE_CANCEL(cancel_state);
return;
}
# endif
if (me -> stop_info.last_stop_count == my_stop_count) {
/* Duplicate signal. OK if we are retrying. */
if (!GC_retry_signals) {
WARN("Duplicate suspend signal in thread %p\n", self);
}
RESTORE_CANCEL(cancel_state);
return;
}
GC_store_stack_ptr(me);
/* Tell the thread that wants to stop the world that this */
/* thread has been stopped. Note that sem_post() is */
/* the only async-signal-safe primitive in LinuxThreads. */
sem_post(&GC_suspend_ack_sem);
AO_store_release(&me->stop_info.last_stop_count, my_stop_count);
# ifdef THREAD_SANITIZER
/* TSan disables signals around signal handlers. Without */
/* a pthread_sigmask call, sigsuspend may block forever. */
{
sigset_t set;
sigemptyset(&set);
if (pthread_sigmask(SIG_SETMASK, &set, NULL) != 0)
ABORT("pthread_sigmask(SIG_SETMASK) failed");
}
# endif
/* Wait until that thread tells us to restart by sending */
/* this thread a GC_sig_thr_restart signal (should be masked */
/* at this point thus there is no race). */
/* We do not continue until we receive that signal, */
/* but we do not take that as authoritative. (We may be */
/* accidentally restarted by one of the user signals we */
/* don't block.) After we receive the signal, we use a */
/* primitive and expensive mechanism to wait until it's */
/* really safe to proceed. Under normal circumstances, */
/* this code should not be executed. */
do {
sigsuspend (&suspend_handler_mask);
} while (AO_load_acquire(&GC_world_is_stopped)
&& AO_load(&GC_stop_count) == my_stop_count);
/* If the RESTART signal gets lost, we can still lose. That should */
/* be less likely than losing the SUSPEND signal, since we don't do */
/* much between the sem_post and sigsuspend. */
/* We'd need more handshaking to work around that. */
/* Simply dropping the sigsuspend call should be safe, but is */
/* unlikely to be efficient. */
# ifdef DEBUG_THREADS
GC_log_printf("Continuing %p\n", (void *)self);
# endif
RESTORE_CANCEL(cancel_state);
}
STATIC void GC_restart_handler(int sig)
{
# if defined(DEBUG_THREADS) || defined(GC_NETBSD_THREADS_WORKAROUND)
int old_errno = errno; /* Preserve errno value. */
# endif
if (sig != GC_sig_thr_restart)
ABORT("Bad signal in restart handler");
# ifdef GC_NETBSD_THREADS_WORKAROUND
sem_post(&GC_restart_ack_sem);
# endif
/*
** Note: even if we don't do anything useful here,
** it would still be necessary to have a signal handler,
** rather than ignoring the signals, otherwise
** the signals will not be delivered at all, and
** will thus not interrupt the sigsuspend() above.
*/
# ifdef DEBUG_THREADS
GC_log_printf("In GC_restart_handler for %p\n", (void *)pthread_self());
# endif
# if defined(DEBUG_THREADS) || defined(GC_NETBSD_THREADS_WORKAROUND)
errno = old_errno;
# endif
}
# ifdef USE_TKILL_ON_ANDROID
extern int tkill(pid_t tid, int sig); /* from sys/linux-unistd.h */
static int android_thread_kill(pid_t tid, int sig)
{
int ret;
int old_errno = errno;
ret = tkill(tid, sig);
if (ret < 0) {
ret = errno;
errno = old_errno;
}
return ret;
}
# define THREAD_SYSTEM_ID(t) (t)->kernel_id
# define RAISE_SIGNAL(t, sig) android_thread_kill(THREAD_SYSTEM_ID(t), sig)
# else
# define THREAD_SYSTEM_ID(t) (t)->id
# define RAISE_SIGNAL(t, sig) pthread_kill(THREAD_SYSTEM_ID(t), sig)
# endif /* !USE_TKILL_ON_ANDROID */
# ifdef GC_ENABLE_SUSPEND_THREAD
# include <sys/time.h>
STATIC void GC_brief_async_signal_safe_sleep(void)
{
struct timeval tv;
tv.tv_sec = 0;
# if defined(GC_TIME_LIMIT) && !defined(CPPCHECK)
tv.tv_usec = 1000 * GC_TIME_LIMIT / 2;
# else
tv.tv_usec = 1000 * 50 / 2;
# endif
(void)select(0, 0, 0, 0, &tv);
}
static void *GC_CALLBACK suspend_self_inner(void *client_data) {
GC_thread me = (GC_thread)client_data;
while (AO_load_acquire(&me->suspended_ext)) {
/* TODO: Use sigsuspend() instead. */
GC_brief_async_signal_safe_sleep();
}
return NULL;
}
GC_API void GC_CALL GC_suspend_thread(GC_SUSPEND_THREAD_ID thread) {
GC_thread t;
IF_CANCEL(int cancel_state;)
DCL_LOCK_STATE;
LOCK();
t = GC_lookup_thread((pthread_t)thread);
if (t == NULL || t -> suspended_ext) {
UNLOCK();
return;
}
/* Set the flag making the change visible to the signal handler. */
AO_store_release(&t->suspended_ext, TRUE);
if ((pthread_t)thread == pthread_self()) {
UNLOCK();
/* It is safe as "t" cannot become invalid here (no race with */
/* GC_unregister_my_thread). */
(void)GC_do_blocking(suspend_self_inner, t);
return;
}
if ((t -> flags & FINISHED) != 0) {
/* Terminated but not joined yet. */
UNLOCK();
return;
}
DISABLE_CANCEL(cancel_state);
/* GC_suspend_thread is not a cancellation point. */
# ifdef PARALLEL_MARK
/* Ensure we do not suspend a thread while it is rebuilding */
/* a free list, otherwise such a dead-lock is possible: */
/* thread 1 is blocked in GC_wait_for_reclaim holding */
/* the allocation lock, thread 2 is suspended in */
/* GC_reclaim_generic invoked from GC_generic_malloc_many */
/* (with GC_fl_builder_count > 0), and thread 3 is blocked */
/* acquiring the allocation lock in GC_resume_thread. */
if (GC_parallel)
GC_wait_for_reclaim();
# endif
/* TODO: Support GC_retry_signals (not needed for TSan) */
switch (RAISE_SIGNAL(t, GC_sig_suspend)) {
/* ESRCH cannot happen as terminated threads are handled above. */
case 0:
break;
default:
ABORT("pthread_kill failed");
}
/* Wait for the thread to complete threads table lookup and */
/* stack_ptr assignment. */
GC_ASSERT(GC_thr_initialized);
while (sem_wait(&GC_suspend_ack_sem) != 0) {
if (errno != EINTR)
ABORT("sem_wait for handler failed (suspend_self)");
}
RESTORE_CANCEL(cancel_state);
UNLOCK();
}
GC_API void GC_CALL GC_resume_thread(GC_SUSPEND_THREAD_ID thread) {
GC_thread t;
DCL_LOCK_STATE;
LOCK();
t = GC_lookup_thread((pthread_t)thread);
if (t != NULL)
AO_store(&t->suspended_ext, FALSE);
UNLOCK();
}
GC_API int GC_CALL GC_is_thread_suspended(GC_SUSPEND_THREAD_ID thread) {
GC_thread t;
int is_suspended = 0;
DCL_LOCK_STATE;
LOCK();
t = GC_lookup_thread((pthread_t)thread);
if (t != NULL && t -> suspended_ext)
is_suspended = (int)TRUE;
UNLOCK();
return is_suspended;
}
# endif /* GC_ENABLE_SUSPEND_THREAD */
#endif /* !GC_OPENBSD_UTHREADS && !NACL */
#ifdef IA64
# define IF_IA64(x) x
#else
# define IF_IA64(x)
#endif
/* We hold allocation lock. Should do exactly the right thing if the */
/* world is stopped. Should not fail if it isn't. */
GC_INNER void GC_push_all_stacks(void)
{
GC_bool found_me = FALSE;
size_t nthreads = 0;
int i;
GC_thread p;
ptr_t lo, hi;
/* On IA64, we also need to scan the register backing store. */
IF_IA64(ptr_t bs_lo; ptr_t bs_hi;)
struct GC_traced_stack_sect_s *traced_stack_sect;
pthread_t self = pthread_self();
word total_size = 0;
if (!EXPECT(GC_thr_initialized, TRUE))
GC_thr_init();
# ifdef DEBUG_THREADS
GC_log_printf("Pushing stacks from thread %p\n", (void *)self);
# endif
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (p -> flags & FINISHED) continue;
++nthreads;
traced_stack_sect = p -> traced_stack_sect;
if (THREAD_EQUAL(p -> id, self)) {
GC_ASSERT(!p->thread_blocked);
# ifdef SPARC
lo = (ptr_t)GC_save_regs_in_stack();
# else
lo = GC_approx_sp();
# endif
found_me = TRUE;
IF_IA64(bs_hi = (ptr_t)GC_save_regs_in_stack();)
} else {
lo = (ptr_t)AO_load((volatile AO_t *)&p->stop_info.stack_ptr);
IF_IA64(bs_hi = p -> backing_store_ptr;)
if (traced_stack_sect != NULL
&& traced_stack_sect->saved_stack_ptr == lo) {
/* If the thread has never been stopped since the recent */
/* GC_call_with_gc_active invocation then skip the top */
/* "stack section" as stack_ptr already points to. */
traced_stack_sect = traced_stack_sect->prev;
}
}
if ((p -> flags & MAIN_THREAD) == 0) {
hi = p -> stack_end;
IF_IA64(bs_lo = p -> backing_store_end);
} else {
/* The original stack. */
hi = GC_stackbottom;
IF_IA64(bs_lo = BACKING_STORE_BASE;)
}
# ifdef DEBUG_THREADS
GC_log_printf("Stack for thread %p = [%p,%p)\n",
(void *)p->id, (void *)lo, (void *)hi);
# endif
if (0 == lo) ABORT("GC_push_all_stacks: sp not set!");
if (p->altstack != NULL && (word)p->altstack <= (word)lo
&& (word)lo <= (word)p->altstack + p->altstack_size) {
hi = p->altstack + p->altstack_size;
/* FIXME: Need to scan the normal stack too, but how ? */
/* FIXME: Assume stack grows down */
}
GC_push_all_stack_sections(lo, hi, traced_stack_sect);
# ifdef STACK_GROWS_UP
total_size += lo - hi;
# else
total_size += hi - lo; /* lo <= hi */
# endif
# ifdef NACL
/* Push reg_storage as roots, this will cover the reg context. */
GC_push_all_stack((ptr_t)p -> stop_info.reg_storage,
(ptr_t)(p -> stop_info.reg_storage + NACL_GC_REG_STORAGE_SIZE));
total_size += NACL_GC_REG_STORAGE_SIZE * sizeof(ptr_t);
# endif
# ifdef IA64
# ifdef DEBUG_THREADS
GC_log_printf("Reg stack for thread %p = [%p,%p)\n",
(void *)p->id, (void *)bs_lo, (void *)bs_hi);
# endif
/* FIXME: This (if p->id==self) may add an unbounded number of */
/* entries, and hence overflow the mark stack, which is bad. */
GC_push_all_register_sections(bs_lo, bs_hi,
THREAD_EQUAL(p -> id, self),
traced_stack_sect);
total_size += bs_hi - bs_lo; /* bs_lo <= bs_hi */
# endif
}
}
GC_VERBOSE_LOG_PRINTF("Pushed %d thread stacks\n", (int)nthreads);
if (!found_me && !GC_in_thread_creation)
ABORT("Collecting from unknown thread");
GC_total_stacksize = total_size;
}
#ifdef DEBUG_THREADS
/* There seems to be a very rare thread stopping problem. To help us */
/* debug that, we save the ids of the stopping thread. */
pthread_t GC_stopping_thread;
int GC_stopping_pid = 0;
#endif
/* We hold the allocation lock. Suspend all threads that might */
/* still be running. Return the number of suspend signals that */
/* were sent. */
STATIC int GC_suspend_all(void)
{
int n_live_threads = 0;
int i;
# ifndef NACL
GC_thread p;
# ifndef GC_OPENBSD_UTHREADS
int result;
# endif
pthread_t self = pthread_self();
# ifdef DEBUG_THREADS
GC_stopping_thread = self;
GC_stopping_pid = getpid();
# endif
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (!THREAD_EQUAL(p -> id, self)) {
if ((p -> flags & FINISHED) != 0) continue;
if (p -> thread_blocked) /* Will wait */ continue;
# ifndef GC_OPENBSD_UTHREADS
# ifdef GC_ENABLE_SUSPEND_THREAD
if (p -> suspended_ext) continue;
# endif
if (AO_load(&p->stop_info.last_stop_count) == GC_stop_count)
continue;
n_live_threads++;
# endif
# ifdef DEBUG_THREADS
GC_log_printf("Sending suspend signal to %p\n", (void *)p->id);
# endif
# ifdef GC_OPENBSD_UTHREADS
{
stack_t stack;
if (pthread_suspend_np(p -> id) != 0)
ABORT("pthread_suspend_np failed");
if (pthread_stackseg_np(p->id, &stack))
ABORT("pthread_stackseg_np failed");
p -> stop_info.stack_ptr = (ptr_t)stack.ss_sp - stack.ss_size;
if (GC_on_thread_event)
GC_on_thread_event(GC_EVENT_THREAD_SUSPENDED,
(void *)p->id);
}
# else
result = RAISE_SIGNAL(p, GC_sig_suspend);
switch(result) {
case ESRCH:
/* Not really there anymore. Possible? */
n_live_threads--;
break;
case 0:
if (GC_on_thread_event)
GC_on_thread_event(GC_EVENT_THREAD_SUSPENDED,
(void *)(word)THREAD_SYSTEM_ID(p));
/* Note: thread id might be truncated. */
break;
default:
ABORT_ARG1("pthread_kill failed at suspend",
": errcode= %d", result);
}
# endif
}
}
}
# else /* NACL */
# ifndef NACL_PARK_WAIT_NANOSECONDS
# define NACL_PARK_WAIT_NANOSECONDS (100 * 1000)
# endif
# define NANOS_PER_SECOND (1000UL * 1000 * 1000)
unsigned long num_sleeps = 0;
# ifdef DEBUG_THREADS
GC_log_printf("pthread_stop_world: num_threads %d\n",
GC_nacl_num_gc_threads - 1);
# endif
GC_nacl_thread_parker = pthread_self();
GC_nacl_park_threads_now = 1;
# ifdef DEBUG_THREADS
GC_stopping_thread = GC_nacl_thread_parker;
GC_stopping_pid = getpid();
# endif
while (1) {
int num_threads_parked = 0;
struct timespec ts;
int num_used = 0;
/* Check the 'parked' flag for each thread the GC knows about. */
for (i = 0; i < MAX_NACL_GC_THREADS
&& num_used < GC_nacl_num_gc_threads; i++) {
if (GC_nacl_thread_used[i] == 1) {
num_used++;
if (GC_nacl_thread_parked[i] == 1) {
num_threads_parked++;
if (GC_on_thread_event)
GC_on_thread_event(GC_EVENT_THREAD_SUSPENDED, (void *)(word)i);
}
}
}
/* -1 for the current thread. */
if (num_threads_parked >= GC_nacl_num_gc_threads - 1)
break;
ts.tv_sec = 0;
ts.tv_nsec = NACL_PARK_WAIT_NANOSECONDS;
# ifdef DEBUG_THREADS
GC_log_printf("Sleep waiting for %d threads to park...\n",
GC_nacl_num_gc_threads - num_threads_parked - 1);
# endif
/* This requires _POSIX_TIMERS feature. */
nanosleep(&ts, 0);
if (++num_sleeps > NANOS_PER_SECOND / NACL_PARK_WAIT_NANOSECONDS) {
WARN("GC appears stalled waiting for %" WARN_PRIdPTR
" threads to park...\n",
GC_nacl_num_gc_threads - num_threads_parked - 1);
num_sleeps = 0;
}
}
# endif /* NACL */
return n_live_threads;
}
GC_INNER void GC_stop_world(void)
{
# if !defined(GC_OPENBSD_UTHREADS) && !defined(NACL)
int i;
int n_live_threads;
int code;
# endif
GC_ASSERT(I_HOLD_LOCK());
# ifdef DEBUG_THREADS
GC_log_printf("Stopping the world from %p\n", (void *)pthread_self());
# endif
/* Make sure all free list construction has stopped before we start. */
/* No new construction can start, since free list construction is */
/* required to acquire and release the GC lock before it starts, */
/* and we have the lock. */
# ifdef PARALLEL_MARK
if (GC_parallel) {
GC_acquire_mark_lock();
GC_ASSERT(GC_fl_builder_count == 0);
/* We should have previously waited for it to become zero. */
}
# endif /* PARALLEL_MARK */
# if defined(GC_OPENBSD_UTHREADS) || defined(NACL)
(void)GC_suspend_all();
# else
AO_store(&GC_stop_count, GC_stop_count+1);
/* Only concurrent reads are possible. */
AO_store_release(&GC_world_is_stopped, TRUE);
n_live_threads = GC_suspend_all();
if (GC_retry_signals && n_live_threads > 0) {
unsigned long wait_usecs = 0; /* Total wait since retry. */
# define WAIT_UNIT 3000
# define RETRY_INTERVAL 100000
for (;;) {
int ack_count;
sem_getvalue(&GC_suspend_ack_sem, &ack_count);
if (ack_count == n_live_threads) break;
if (wait_usecs > RETRY_INTERVAL) {
int newly_sent = GC_suspend_all();
GC_COND_LOG_PRINTF("Resent %d signals after timeout\n", newly_sent);
sem_getvalue(&GC_suspend_ack_sem, &ack_count);
if (newly_sent < n_live_threads - ack_count) {
WARN("Lost some threads during GC_stop_world?!\n",0);
n_live_threads = ack_count + newly_sent;
}
wait_usecs = 0;
}
# ifdef LINT2
/* Workaround "waiting while holding a lock" warning. */
# undef WAIT_UNIT
# define WAIT_UNIT 1
sched_yield();
# elif defined(CPPCHECK) /* || _POSIX_C_SOURCE >= 199309L */
{
struct timespec ts;
ts.tv_sec = 0;
ts.tv_nsec = WAIT_UNIT * 1000;
(void)nanosleep(&ts, NULL);
}
# else
usleep(WAIT_UNIT);
# endif
wait_usecs += WAIT_UNIT;
}
}
for (i = 0; i < n_live_threads; i++) {
retry:
code = sem_wait(&GC_suspend_ack_sem);
if (0 != code) {
/* On Linux, sem_wait is documented to always return zero. */
/* But the documentation appears to be incorrect. */
if (errno == EINTR) {
/* Seems to happen with some versions of gdb. */
goto retry;
}
ABORT("sem_wait for handler failed");
}
}
# endif
# ifdef PARALLEL_MARK
if (GC_parallel)
GC_release_mark_lock();
# endif
# ifdef DEBUG_THREADS
GC_log_printf("World stopped from %p\n", (void *)pthread_self());
GC_stopping_thread = 0;
# endif
}
#ifdef NACL
# if defined(__x86_64__)
# define NACL_STORE_REGS() \
do { \
__asm__ __volatile__ ("push %rbx"); \
__asm__ __volatile__ ("push %rbp"); \
__asm__ __volatile__ ("push %r12"); \
__asm__ __volatile__ ("push %r13"); \
__asm__ __volatile__ ("push %r14"); \
__asm__ __volatile__ ("push %r15"); \
__asm__ __volatile__ ("mov %%esp, %0" \
: "=m" (GC_nacl_gc_thread_self->stop_info.stack_ptr)); \
BCOPY(GC_nacl_gc_thread_self->stop_info.stack_ptr, \
GC_nacl_gc_thread_self->stop_info.reg_storage, \
NACL_GC_REG_STORAGE_SIZE * sizeof(ptr_t)); \
__asm__ __volatile__ ("naclasp $48, %r15"); \
} while (0)
# elif defined(__i386__)
# define NACL_STORE_REGS() \
do { \
__asm__ __volatile__ ("push %ebx"); \
__asm__ __volatile__ ("push %ebp"); \
__asm__ __volatile__ ("push %esi"); \
__asm__ __volatile__ ("push %edi"); \
__asm__ __volatile__ ("mov %%esp, %0" \
: "=m" (GC_nacl_gc_thread_self->stop_info.stack_ptr)); \
BCOPY(GC_nacl_gc_thread_self->stop_info.stack_ptr, \
GC_nacl_gc_thread_self->stop_info.reg_storage, \
NACL_GC_REG_STORAGE_SIZE * sizeof(ptr_t));\
__asm__ __volatile__ ("add $16, %esp"); \
} while (0)
# elif defined(__arm__)
# define NACL_STORE_REGS() \
do { \
__asm__ __volatile__ ("push {r4-r8,r10-r12,lr}"); \
__asm__ __volatile__ ("mov r0, %0" \
: : "r" (&GC_nacl_gc_thread_self->stop_info.stack_ptr)); \
__asm__ __volatile__ ("bic r0, r0, #0xc0000000"); \
__asm__ __volatile__ ("str sp, [r0]"); \
BCOPY(GC_nacl_gc_thread_self->stop_info.stack_ptr, \
GC_nacl_gc_thread_self->stop_info.reg_storage, \
NACL_GC_REG_STORAGE_SIZE * sizeof(ptr_t)); \
__asm__ __volatile__ ("add sp, sp, #40"); \
__asm__ __volatile__ ("bic sp, sp, #0xc0000000"); \
} while (0)
# else
# error TODO Please port NACL_STORE_REGS
# endif
GC_API_OSCALL void nacl_pre_syscall_hook(void)
{
if (GC_nacl_thread_idx != -1) {
NACL_STORE_REGS();
GC_nacl_gc_thread_self->stop_info.stack_ptr = GC_approx_sp();
GC_nacl_thread_parked[GC_nacl_thread_idx] = 1;
}
}
GC_API_OSCALL void __nacl_suspend_thread_if_needed(void)
{
if (GC_nacl_park_threads_now) {
pthread_t self = pthread_self();
/* Don't try to park the thread parker. */
if (GC_nacl_thread_parker == self)
return;
/* This can happen when a thread is created outside of the GC */
/* system (wthread mostly). */
if (GC_nacl_thread_idx < 0)
return;
/* If it was already 'parked', we're returning from a syscall, */
/* so don't bother storing registers again, the GC has a set. */
if (!GC_nacl_thread_parked[GC_nacl_thread_idx]) {
NACL_STORE_REGS();
GC_nacl_gc_thread_self->stop_info.stack_ptr = GC_approx_sp();
}
GC_nacl_thread_parked[GC_nacl_thread_idx] = 1;
while (GC_nacl_park_threads_now) {
/* Just spin. */
}
GC_nacl_thread_parked[GC_nacl_thread_idx] = 0;
/* Clear out the reg storage for next suspend. */
BZERO(GC_nacl_gc_thread_self->stop_info.reg_storage,
NACL_GC_REG_STORAGE_SIZE * sizeof(ptr_t));
}
}
GC_API_OSCALL void nacl_post_syscall_hook(void)
{
/* Calling __nacl_suspend_thread_if_needed right away should */
/* guarantee we don't mutate the GC set. */
__nacl_suspend_thread_if_needed();
if (GC_nacl_thread_idx != -1) {
GC_nacl_thread_parked[GC_nacl_thread_idx] = 0;
}
}
STATIC GC_bool GC_nacl_thread_parking_inited = FALSE;
STATIC pthread_mutex_t GC_nacl_thread_alloc_lock = PTHREAD_MUTEX_INITIALIZER;
struct nacl_irt_blockhook {
int (*register_block_hooks)(void (*pre)(void), void (*post)(void));
};
extern size_t nacl_interface_query(const char *interface_ident,
void *table, size_t tablesize);
GC_INNER void GC_nacl_initialize_gc_thread(void)
{
int i;
static struct nacl_irt_blockhook gc_hook;
pthread_mutex_lock(&GC_nacl_thread_alloc_lock);
if (!EXPECT(GC_nacl_thread_parking_inited, TRUE)) {
BZERO(GC_nacl_thread_parked, sizeof(GC_nacl_thread_parked));
BZERO(GC_nacl_thread_used, sizeof(GC_nacl_thread_used));
/* TODO: replace with public 'register hook' function when */
/* available from glibc. */
nacl_interface_query("nacl-irt-blockhook-0.1",