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pthread_stop_world.c
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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.
* Copyright (c) 2008-2022 Ivan Maidanski
*
* 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"
#ifdef PTHREAD_STOP_WORLD_IMPL
#ifdef NACL
# include <sys/time.h>
#else
# include <signal.h>
# include <semaphore.h>
# include <errno.h>
# include <time.h> /* for nanosleep() */
#endif /* !NACL */
#ifdef E2K
# include <alloca.h>
#endif
# include <link.h>
GC_INLINE void GC_usleep(unsigned us)
{
# if defined(LINT2) || defined(THREAD_SANITIZER)
/* Workaround "waiting while holding a lock" static analyzer warning. */
/* Workaround a rare hang in usleep() trying to acquire TSan Lock. */
while (us-- > 0)
sched_yield(); /* pretending it takes 1us */
# elif defined(CPPCHECK) /* || _POSIX_C_SOURCE >= 199309L */
struct timespec ts;
ts.tv_sec = 0;
ts.tv_nsec = (unsigned32)us * 1000;
/* This requires _POSIX_TIMERS feature. */
(void)nanosleep(&ts, NULL);
# else
usleep(us);
# endif
}
#ifdef NACL
STATIC int GC_nacl_num_gc_threads = 0;
STATIC volatile int GC_nacl_park_threads_now = 0;
STATIC volatile pthread_t GC_nacl_thread_parker = -1;
STATIC __thread int GC_nacl_thread_idx = -1;
STATIC __thread GC_thread GC_nacl_gc_thread_self = NULL;
/* TODO: Use GC_get_tlfs() instead. */
volatile int GC_nacl_thread_parked[MAX_NACL_GC_THREADS];
int GC_nacl_thread_used[MAX_NACL_GC_THREADS];
#else
#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
#ifdef DEBUG_THREADS
/* It's safe to call original pthread_sigmask() here. */
# undef pthread_sigmask
# ifndef NSIG
# ifdef CPPCHECK
# define NSIG 32
# elif 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;
#define THREAD_RESTARTED 0x1
STATIC volatile AO_t GC_stop_count;
/* Incremented (to the nearest even value) at */
/* the beginning of GC_stop_world() (or when */
/* a thread is requested to be suspended by */
/* GC_suspend_thread) and once more (to an odd */
/* value) at the beginning of GC_start_world(). */
/* The lowest bit is THREAD_RESTARTED one */
/* which, if set, means 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). */
STATIC GC_bool GC_retry_signals = FALSE;
/*
* 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
# ifdef SUSPEND_HANDLER_NO_CONTEXT
/* Reuse the suspend signal. */
# define SIG_THR_RESTART SIG_SUSPEND
# elif 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
# elif defined(GC_FREEBSD_THREADS) && defined(__GLIBC__)
# define SIG_THR_RESTART (32+5)
# elif defined(GC_FREEBSD_THREADS) || defined(HURD) || defined(RTEMS)
# define SIG_THR_RESTART SIGUSR2
# else
# define SIG_THR_RESTART SIGXCPU
# endif
#endif /* !SIG_THR_RESTART */
#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). */
/* Might be set to the same signal number. */
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 BASE_ATOMIC_OPS_EMULATED
/* The AO primitives emulated with locks cannot be used inside signal */
/* handlers as this could cause a deadlock or a double lock. */
/* The following "async" macro definitions are correct only for */
/* an uniprocessor case and are provided for a test purpose. */
# define ao_load_acquire_async(p) (*(p))
# define ao_load_async(p) ao_load_acquire_async(p)
# define ao_store_release_async(p, v) (void)(*(p) = (v))
# define ao_store_async(p, v) ao_store_release_async(p, v)
#else
# define ao_load_acquire_async(p) AO_load_acquire(p)
# define ao_load_async(p) AO_load(p)
# define ao_store_release_async(p, v) AO_store_release(p, v)
# define ao_store_async(p, v) AO_store(p, v)
#endif /* !BASE_ATOMIC_OPS_EMULATED */
STATIC sem_t GC_suspend_ack_sem; /* also used to acknowledge restart */
STATIC void GC_suspend_handler_inner(ptr_t dummy, void *context);
#ifdef SUSPEND_HANDLER_NO_CONTEXT
STATIC void GC_suspend_handler(int sig)
#else
STATIC void GC_suspend_sigaction(int sig, siginfo_t *info, void *context)
#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");
}
# ifdef SUSPEND_HANDLER_NO_CONTEXT
/* A quick check if the signal is called to restart the world. */
if ((ao_load_async(&GC_stop_count) & THREAD_RESTARTED) != 0)
return;
GC_with_callee_saves_pushed(GC_suspend_handler_inner, NULL);
# else
UNUSED_ARG(info);
/* We believe that in this case the full context is already */
/* in the signal handler frame. */
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 allocator 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
/* Almost same as GC_self_thread_inner() except for the */
/* no-sanitize attribute added and the result is never NULL. */
GC_ATTR_NO_SANITIZE_THREAD
static GC_thread GC_lookup_self_thread_async(void)
{
thread_id_t self_id = thread_id_self();
GC_thread p = GC_threads[THREAD_TABLE_INDEX(self_id)];
for (;; p = p -> tm.next) {
if (THREAD_EQUAL(p -> id, self_id)) break;
}
return p;
}
#else
# define GC_lookup_self_thread_async() GC_self_thread_inner()
#endif
GC_INLINE void GC_store_stack_ptr(GC_stack_context_t crtn)
{
/* 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_async((volatile AO_t *)&(crtn -> stack_ptr),
(AO_t)GC_save_regs_in_stack());
/* TODO: regs saving already done by GC_with_callee_saves_pushed */
# else
# ifdef IA64
crtn -> backing_store_ptr = GC_save_regs_in_stack();
# endif
ao_store_async((volatile AO_t *)&(crtn -> stack_ptr),
(AO_t)GC_approx_sp());
# endif
}
static int find_segment(struct dl_phdr_info *info, size_t size, void *data) {
UNUSED_ARG(size);
tlr * roots = (tlr *) data;
for (size_t i = 0; i < info->dlpi_phnum; i ++) {
if ( info -> dlpi_phdr[i].p_type != PT_TLS )
continue;
if ( info -> dlpi_tls_data == NULL )
/* This SO has no thread locals */
return 0;
size_t memsz = info -> dlpi_phdr[i].p_memsz;
ptr_t start = info -> dlpi_tls_data;
GC_ASSERT(memsz > 0);
roots -> start = start;
roots -> end = start + memsz;
return 1;
}
return 0;
}
/* Get the TLS roots for the current thread. */
/* */
/* This works because a Rust program (and any shared objects) use the PT_TLS */
/* segment in the binary to store every thread's local instance of each */
/* thread-local variable. For each thread, these instances are stored at a */
/* fixed offset inside the same PT_TLS segment [1]. */
/* */
/* This returns the ranges inside the `PT_TLS` segment which contains the */
/* thread-local instances for the current thread only. */
/* */
/* [1]: https://www.akkadia.org/drepper/tls.pdf */
void get_thread_local_roots(tlr * roots)
{
dl_iterate_phdr(find_segment, roots);
return;
}
STATIC void GC_suspend_handler_inner(ptr_t dummy, void *context)
{
GC_thread me;
GC_stack_context_t crtn;
struct GC_ThreadLocalRoots tlr;
# ifdef E2K
ptr_t bs_lo;
size_t stack_size;
# endif
IF_CANCEL(int cancel_state;)
# ifdef GC_ENABLE_SUSPEND_THREAD
word suspend_cnt;
# endif
AO_t my_stop_count = ao_load_acquire_async(&GC_stop_count);
/* After the barrier, this thread should see */
/* the actual content of GC_threads. */
UNUSED_ARG(dummy);
UNUSED_ARG(context);
if ((my_stop_count & THREAD_RESTARTED) != 0)
return; /* Restarting the world. */
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 *)pthread_self());
# endif
me = GC_lookup_self_thread_async();
if ((me -> last_stop_count & ~(word)THREAD_RESTARTED) == my_stop_count) {
/* Duplicate signal. OK if we are retrying. */
if (!GC_retry_signals) {
WARN("Duplicate suspend signal in thread %p\n", pthread_self());
}
RESTORE_CANCEL(cancel_state);
return;
}
crtn = me -> crtn;
GC_store_stack_ptr(crtn);
get_thread_local_roots(&tlr);
crtn -> compiler_thread_roots = tlr;
# ifdef E2K
GC_ASSERT(NULL == crtn -> backing_store_end);
GET_PROCEDURE_STACK_LOCAL(crtn -> ps_ofs, &bs_lo, &stack_size);
crtn -> backing_store_end = bs_lo;
crtn -> backing_store_ptr = bs_lo + stack_size;
# endif
# ifdef GC_ENABLE_SUSPEND_THREAD
suspend_cnt = (word)ao_load_async(&(me -> ext_suspend_cnt));
# endif
/* 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_async(&(me -> last_stop_count), my_stop_count);
/* 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);
/* Iterate while not restarting the world or thread is suspended. */
} while (ao_load_acquire_async(&GC_stop_count) == my_stop_count
# ifdef GC_ENABLE_SUSPEND_THREAD
|| ((suspend_cnt & 1) != 0
&& (word)ao_load_async(&(me -> ext_suspend_cnt))
== suspend_cnt)
# endif
);
# ifdef DEBUG_THREADS
GC_log_printf("Resuming %p\n", (void *)pthread_self());
# endif
# ifdef E2K
GC_ASSERT(crtn -> backing_store_end == bs_lo);
crtn -> backing_store_ptr = NULL;
crtn -> backing_store_end = NULL;
# endif
# ifndef GC_NETBSD_THREADS_WORKAROUND
if (GC_retry_signals || GC_sig_suspend == GC_sig_thr_restart)
# endif
{
/* If the RESTART signal loss is possible (though it should be */
/* less likely than losing the SUSPEND signal as we do not do */
/* much between the first sem_post and sigsuspend calls), more */
/* handshaking is provided to work around it. */
sem_post(&GC_suspend_ack_sem);
/* Set the flag that the thread has been restarted. */
if (GC_retry_signals)
ao_store_release_async(&(me -> last_stop_count),
my_stop_count | THREAD_RESTARTED);
}
RESTORE_CANCEL(cancel_state);
}
static void suspend_restart_barrier(int n_live_threads)
{
int i;
for (i = 0; i < n_live_threads; i++) {
while (0 != sem_wait(&GC_suspend_ack_sem)) {
/* On Linux, sem_wait is documented to always return zero. */
/* But the documentation appears to be incorrect. */
/* EINTR seems to happen with some versions of gdb. */
if (errno != EINTR)
ABORT("sem_wait failed");
}
}
# ifdef GC_ASSERTIONS
sem_getvalue(&GC_suspend_ack_sem, &i);
GC_ASSERT(0 == i);
# endif
}
# define WAIT_UNIT 3000 /* us */
static int resend_lost_signals(int n_live_threads,
int (*suspend_restart_all)(void))
{
# define RETRY_INTERVAL 100000 /* us */
# define RESEND_SIGNALS_LIMIT 150
if (n_live_threads > 0) {
unsigned long wait_usecs = 0; /* Total wait since retry. */
int retry = 0;
int prev_sent = 0;
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 = suspend_restart_all();
if (newly_sent != prev_sent) {
retry = 0; /* restart the counter */
} else if (++retry >= RESEND_SIGNALS_LIMIT) /* no progress */
ABORT_ARG1("Signals delivery fails constantly",
" at GC #%lu", (unsigned long)GC_gc_no);
GC_COND_LOG_PRINTF("Resent %d signals after timeout, retry: %d\n",
newly_sent, retry);
sem_getvalue(&GC_suspend_ack_sem, &ack_count);
if (newly_sent < n_live_threads - ack_count) {
WARN("Lost some threads while stopping or starting world?!\n", 0);
n_live_threads = ack_count + newly_sent;
}
prev_sent = newly_sent;
wait_usecs = 0;
}
GC_usleep(WAIT_UNIT);
wait_usecs += WAIT_UNIT;
}
}
return n_live_threads;
}
#ifdef HAVE_CLOCK_GETTIME
# define TS_NSEC_ADD(ts, ns) \
(ts.tv_nsec += (ns), \
(void)(ts.tv_nsec >= 1000000L*1000 ? \
(ts.tv_nsec -= 1000000L*1000, ts.tv_sec++, 0) : 0))
#endif
static void resend_lost_signals_retry(int n_live_threads,
int (*suspend_restart_all)(void))
{
# if defined(HAVE_CLOCK_GETTIME) && !defined(DONT_TIMEDWAIT_ACK_SEM)
# define TIMEOUT_BEFORE_RESEND 10000 /* us */
struct timespec ts;
if (n_live_threads > 0 && clock_gettime(CLOCK_REALTIME, &ts) == 0) {
int i;
TS_NSEC_ADD(ts, TIMEOUT_BEFORE_RESEND * (unsigned32)1000);
/* First, try to wait for the semaphore with some timeout. */
/* On failure, fallback to WAIT_UNIT pause and resend of the signal. */
for (i = 0; i < n_live_threads; i++) {
if (0 != sem_timedwait(&GC_suspend_ack_sem, &ts))
break; /* Wait timed out or any other error. */
}
/* Update the count of threads to wait the ack from. */
n_live_threads -= i;
}
# endif
n_live_threads = resend_lost_signals(n_live_threads, suspend_restart_all);
suspend_restart_barrier(n_live_threads);
}
STATIC void GC_restart_handler(int sig)
{
# if defined(DEBUG_THREADS)
int old_errno = errno; /* Preserve errno value. */
# endif
if (sig != GC_sig_thr_restart)
ABORT("Bad signal in restart handler");
/* Note: even if we do not 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());
errno = old_errno;
# endif
}
# ifdef USE_TKILL_ON_ANDROID
EXTERN_C_BEGIN
extern int tkill(pid_t tid, int sig); /* from sys/linux-unistd.h */
EXTERN_C_END
# define THREAD_SYSTEM_ID(t) (t)->kernel_id
# else
# define THREAD_SYSTEM_ID(t) (t)->id
# endif
# ifndef RETRY_TKILL_EAGAIN_LIMIT
# define RETRY_TKILL_EAGAIN_LIMIT 16
# endif
static int raise_signal(GC_thread p, int sig)
{
int res;
# ifdef RETRY_TKILL_ON_EAGAIN
int retry;
# endif
# if defined(SIMULATE_LOST_SIGNALS) && !defined(GC_ENABLE_SUSPEND_THREAD)
# ifndef LOST_SIGNALS_RATIO
# define LOST_SIGNALS_RATIO 25
# endif
static int signal_cnt; /* race is OK, it is for test purpose only */
if (GC_retry_signals && (++signal_cnt) % LOST_SIGNALS_RATIO == 0)
return 0; /* simulate the signal is sent but lost */
# endif
# ifdef RETRY_TKILL_ON_EAGAIN
for (retry = 0;; retry++)
# endif
{
# ifdef USE_TKILL_ON_ANDROID
int old_errno = errno;
res = tkill(THREAD_SYSTEM_ID(p), sig);
if (res < 0) {
res = errno;
errno = old_errno;
}
# else
res = pthread_kill(THREAD_SYSTEM_ID(p), sig);
# endif
# ifdef RETRY_TKILL_ON_EAGAIN
if (res != EAGAIN || retry >= RETRY_TKILL_EAGAIN_LIMIT) break;
/* A temporal overflow of the real-time signal queue. */
GC_usleep(WAIT_UNIT);
# endif
}
return res;
}
# ifdef GC_ENABLE_SUSPEND_THREAD
# include <sys/time.h>
# include "gc/javaxfc.h" /* to get the prototypes as extern "C" */
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 * 15 / 2;
# endif
(void)select(0, 0, 0, 0, &tv);
}
GC_INNER void GC_suspend_self_inner(GC_thread me, word suspend_cnt) {
IF_CANCEL(int cancel_state;)
GC_ASSERT((suspend_cnt & 1) != 0);
DISABLE_CANCEL(cancel_state);
# ifdef DEBUG_THREADS
GC_log_printf("Suspend self: %p\n", (void *)(me -> id));
# endif
while ((word)ao_load_acquire_async(&(me -> ext_suspend_cnt))
== suspend_cnt) {
/* TODO: Use sigsuspend() even for self-suspended threads. */
GC_brief_async_signal_safe_sleep();
}
# ifdef DEBUG_THREADS
GC_log_printf("Resume self: %p\n", (void *)(me -> id));
# endif
RESTORE_CANCEL(cancel_state);
}
GC_API void GC_CALL GC_suspend_thread(GC_SUSPEND_THREAD_ID thread) {
GC_thread t;
AO_t next_stop_count;
word suspend_cnt;
IF_CANCEL(int cancel_state;)
LOCK();
t = GC_lookup_by_pthread((pthread_t)thread);
if (NULL == t) {
UNLOCK();
return;
}
suspend_cnt = (word)(t -> ext_suspend_cnt);
if ((suspend_cnt & 1) != 0) /* already suspended? */ {
GC_ASSERT(!THREAD_EQUAL((pthread_t)thread, pthread_self()));
UNLOCK();
return;
}
if ((t -> flags & (FINISHED | DO_BLOCKING)) != 0) {
t -> ext_suspend_cnt = (AO_t)(suspend_cnt | 1); /* suspend */
/* Terminated but not joined yet, or in do-blocking state. */
UNLOCK();
return;
}
if (THREAD_EQUAL((pthread_t)thread, pthread_self())) {
t -> ext_suspend_cnt = (AO_t)(suspend_cnt | 1);
GC_with_callee_saves_pushed(GC_suspend_self_blocked, (ptr_t)t);
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 deadlock is possible: */
/* thread 1 is blocked in GC_wait_for_reclaim holding */
/* the allocator 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 allocator lock in GC_resume_thread. */
if (GC_parallel)
GC_wait_for_reclaim();
# endif
if (GC_manual_vdb) {
/* See the relevant comment in GC_stop_world. */
GC_acquire_dirty_lock();
}
/* Else do not acquire the dirty lock as the write fault handler */
/* might be trying to acquire it too, and the suspend handler */
/* execution is deferred until the write fault handler completes. */
next_stop_count = GC_stop_count + THREAD_RESTARTED;
GC_ASSERT((next_stop_count & THREAD_RESTARTED) == 0);
AO_store(&GC_stop_count, next_stop_count);
/* Set the flag making the change visible to the signal handler. */
AO_store_release(&(t -> ext_suspend_cnt), (AO_t)(suspend_cnt | 1));
/* 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);
suspend_restart_barrier(1);
if (GC_manual_vdb)
GC_release_dirty_lock();
AO_store(&GC_stop_count, next_stop_count | THREAD_RESTARTED);
RESTORE_CANCEL(cancel_state);
UNLOCK();
}
GC_API void GC_CALL GC_resume_thread(GC_SUSPEND_THREAD_ID thread) {
GC_thread t;
LOCK();
t = GC_lookup_by_pthread((pthread_t)thread);
if (t != NULL) {
word suspend_cnt = (word)(t -> ext_suspend_cnt);
if ((suspend_cnt & 1) != 0) /* is suspended? */ {
GC_ASSERT((GC_stop_count & THREAD_RESTARTED) != 0);
/* Mark the thread as not suspended - it will be resumed shortly. */
AO_store(&(t -> ext_suspend_cnt), (AO_t)(suspend_cnt + 1));
if ((t -> flags & (FINISHED | DO_BLOCKING)) == 0) {
int result = raise_signal(t, GC_sig_thr_restart);
/* TODO: Support signal resending on GC_retry_signals */
if (result != 0)
ABORT_ARG1("pthread_kill failed in GC_resume_thread",
": errcode= %d", result);
# ifndef GC_NETBSD_THREADS_WORKAROUND
if (GC_retry_signals || GC_sig_suspend == GC_sig_thr_restart)
# endif
{
IF_CANCEL(int cancel_state;)
DISABLE_CANCEL(cancel_state);
suspend_restart_barrier(1);
RESTORE_CANCEL(cancel_state);
}
}
}
}
UNLOCK();
}
GC_API int GC_CALL GC_is_thread_suspended(GC_SUSPEND_THREAD_ID thread) {
GC_thread t;
int is_suspended = 0;
READER_LOCK();
t = GC_lookup_by_pthread((pthread_t)thread);
if (t != NULL && (t -> ext_suspend_cnt & 1) != 0)
is_suspended = (int)TRUE;
READER_UNLOCK();
return is_suspended;
}
# endif /* GC_ENABLE_SUSPEND_THREAD */
# undef ao_load_acquire_async
# undef ao_load_async
# undef ao_store_async
# undef ao_store_release_async
#endif /* !NACL */
/* Should do exactly the right thing if the world is stopped; should */
/* not fail if it is not. */
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; /* stack top (sp) */
ptr_t hi; /* bottom */
# if defined(E2K) || defined(IA64)
/* We also need to scan the register backing store. */
ptr_t bs_lo, bs_hi;
# endif
struct GC_traced_stack_sect_s *traced_stack_sect;
pthread_t self = pthread_self();
word total_size = 0;
// We need to push the TLS rootset for the current thread (i.e. the thread
// which invoked GC). The TLS rootset for all other threads is pushed from
// inside their suspend handler.
//
// However, a GC can be scheduled by the current thread while it is being
// registered. This is fine because it won't contain any roots yet -- but it
// does mean that the thread might not have setup a context yet. So we must
// perform null check.
GC_thread me = GC_self_thread_inner();
if (me != NULL) {
struct GC_ThreadLocalRoots tlr;
get_thread_local_roots(&tlr);
me -> crtn -> compiler_thread_roots = tlr;
}
GC_ASSERT(I_HOLD_LOCK());
GC_ASSERT(GC_thr_initialized);
# 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 != NULL; p = p -> tm.next) {
# if defined(E2K) || defined(IA64)
GC_bool is_self = FALSE;
# endif
GC_stack_context_t crtn = p -> crtn;
GC_ASSERT(THREAD_TABLE_INDEX(p -> id) == i);
if (KNOWN_FINISHED(p)) continue;
++nthreads;
traced_stack_sect = crtn -> traced_stack_sect;
if (THREAD_EQUAL(p -> id, self)) {
GC_ASSERT((p -> flags & DO_BLOCKING) == 0);
# ifdef SPARC
lo = GC_save_regs_in_stack();
# else
lo = GC_approx_sp();
# ifdef IA64
bs_hi = GC_save_regs_in_stack();
# elif defined(E2K)
{
size_t stack_size;
GC_ASSERT(NULL == crtn -> backing_store_end);
GET_PROCEDURE_STACK_LOCAL(crtn -> ps_ofs,
&bs_lo, &stack_size);
bs_hi = bs_lo + stack_size;
}
# endif
# endif
found_me = TRUE;
# if defined(E2K) || defined(IA64)
is_self = TRUE;
# endif
} else {
lo = (ptr_t)AO_load((volatile AO_t *)&(crtn -> stack_ptr));
# ifdef IA64
bs_hi = crtn -> backing_store_ptr;
# elif defined(E2K)
bs_lo = crtn -> backing_store_end;
bs_hi = crtn -> backing_store_ptr;
# endif
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;
}
}
hi = crtn -> stack_end;
# ifdef IA64
bs_lo = crtn -> backing_store_end;
# endif
# ifdef DEBUG_THREADS
# ifdef STACK_GROWS_UP
GC_log_printf("Stack for thread %p is (%p,%p]\n",
(void *)(p -> id), (void *)hi, (void *)lo);
# else
GC_log_printf("Stack for thread %p is [%p,%p)\n",
(void *)(p -> id), (void *)lo, (void *)hi);
# endif
GC_log_printf("TLS rootset for thread %p is %p\n",
(void *)(p -> id), crtn -> tls_rootset);
# endif
if (NULL == lo) ABORT("GC_push_all_stacks: sp not set!");
if (crtn -> altstack != NULL && ADDR_GE(lo, crtn -> altstack)
&& ADDR_GE(crtn -> altstack + crtn -> altstack_size, lo)) {
# ifdef STACK_GROWS_UP
hi = crtn -> altstack;
# else
hi = crtn -> altstack + crtn -> altstack_size;
# endif
/* FIXME: Need to scan the normal stack too, but how ? */
}
# ifdef STACKPTR_CORRECTOR_AVAILABLE
if (GC_sp_corrector != 0)
GC_sp_corrector((void **)&lo, (void *)(p -> id));
# endif
/* Scan the TLS roots */
GC_push_all_eager(crtn->compiler_thread_roots.start, crtn->compiler_thread_roots.end);
GC_push_all_stack_sections(lo, hi, traced_stack_sect);
# ifdef DEBUG_THREADS
GC_log_printf("Pushing TLS rootset from thread %p\n",
(void *)(p -> id), crtn -> tls_rootset);
# endif
GC_mark_and_push_stack(crtn->tls_rootset);
# 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 -> reg_storage,
(ptr_t)(p -> reg_storage + NACL_GC_REG_STORAGE_SIZE));
total_size += NACL_GC_REG_STORAGE_SIZE * sizeof(ptr_t);
# endif
# ifdef E2K
if ((GC_stop_count & THREAD_RESTARTED) != 0
# ifdef GC_ENABLE_SUSPEND_THREAD
&& (p -> ext_suspend_cnt & 1) == 0
# endif
&& !is_self && (p -> flags & DO_BLOCKING) == 0)
continue; /* procedure stack buffer has already been freed */
# endif
# if defined(E2K) || defined(IA64)
# ifdef DEBUG_THREADS
GC_log_printf("Reg stack for thread %p is [%p,%p)\n",
(void *)(p -> id), (void *)bs_lo, (void *)bs_hi);
# endif
GC_ASSERT(bs_lo != NULL && bs_hi != NULL);
/* FIXME: This (if is_self) may add an unbounded number of */
/* entries, and hence overflow the mark stack, which is bad. */
# ifdef IA64
GC_push_all_register_sections(bs_lo, bs_hi, is_self,
traced_stack_sect);
# else
if (is_self) {
GC_push_all_eager(bs_lo, bs_hi);
} else {
GC_push_all_stack(bs_lo, bs_hi);
}
# endif
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
/* 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;
pthread_t self = pthread_self();
int result;
GC_ASSERT((GC_stop_count & THREAD_RESTARTED) == 0);
GC_ASSERT(I_HOLD_LOCK());
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != NULL; p = p -> tm.next) {