/*
* Copyright (c) 1994 by Xerox Corporation. All rights reserved.
* Copyright (c) 1996 by Silicon Graphics. 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.
*/
/*
* Support code for Irix (>=6.2) Pthreads. This relies on properties
* not guaranteed by the Pthread standard. It may or may not be portable
* to other implementations.
*
* Note that there is a lot of code duplication between linux_threads.c
* and irix_threads.c; any changes made here may need to be reflected
* there too.
*/
# if defined(IRIX_THREADS)
# include "gc_priv.h"
# include <pthread.h>
# include <semaphore.h>
# include <time.h>
# include <errno.h>
# include <unistd.h>
# include <sys/mman.h>
# include <sys/time.h>
#undef pthread_create
#undef pthread_sigmask
#undef pthread_join
void GC_thr_init();
#if 0
void GC_print_sig_mask()
{
sigset_t blocked;
int i;
if (pthread_sigmask(SIG_BLOCK, NULL, &blocked) != 0)
ABORT("pthread_sigmask");
GC_printf0("Blocked: ");
for (i = 1; i <= MAXSIG; i++) {
if (sigismember(&blocked, i)) { GC_printf1("%ld ",(long) i); }
}
GC_printf0("\n");
}
#endif
/* We use the allocation lock to protect thread-related data structures. */
/* The set of all known threads. We intercept thread creation and */
/* joins. We never actually create detached threads. We allocate all */
/* new thread stacks ourselves. These allow us to maintain this */
/* data structure. */
/* Protected by GC_thr_lock. */
/* Some of this should be declared volatile, but that's incosnsistent */
/* with some library routine declarations. */
typedef struct GC_Thread_Rep {
struct GC_Thread_Rep * next; /* More recently allocated threads */
/* with a given pthread id come */
/* first. (All but the first are */
/* guaranteed to be dead, but we may */
/* not yet have registered the join.) */
pthread_t id;
word stop;
# define NOT_STOPPED 0
# define PLEASE_STOP 1
# define STOPPED 2
word flags;
# define FINISHED 1 /* Thread has exited. */
# define DETACHED 2 /* Thread is intended to be detached. */
# define CLIENT_OWNS_STACK 4
/* Stack was supplied by client. */
ptr_t stack;
ptr_t stack_ptr; /* Valid only when stopped. */
/* But must be within stack region at */
/* all times. */
size_t stack_size; /* 0 for original thread. */
void * status; /* Used only to avoid premature */
/* reclamation of any data it might */
/* reference. */
} * GC_thread;
GC_thread GC_lookup_thread(pthread_t id);
/*
* The only way to suspend threads given the pthread interface is to send
* signals. Unfortunately, this means we have to reserve
* a signal, and intercept client calls to change the signal mask.
*/
# define SIG_SUSPEND (SIGRTMIN + 6)
pthread_mutex_t GC_suspend_lock = PTHREAD_MUTEX_INITIALIZER;
/* Number of threads stopped so far */
pthread_cond_t GC_suspend_ack_cv = PTHREAD_COND_INITIALIZER;
pthread_cond_t GC_continue_cv = PTHREAD_COND_INITIALIZER;
void GC_suspend_handler(int sig)
{
int dummy;
GC_thread me;
sigset_t all_sigs;
sigset_t old_sigs;
int i;
if (sig != SIG_SUSPEND) ABORT("Bad signal in suspend_handler");
me = GC_lookup_thread(pthread_self());
/* The lookup here is safe, since I'm doing this 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. */
if (PLEASE_STOP != me -> stop) {
/* Misdirected signal. */
pthread_mutex_unlock(&GC_suspend_lock);
return;
}
pthread_mutex_lock(&GC_suspend_lock);
me -> stack_ptr = (ptr_t)(&dummy);
me -> stop = STOPPED;
pthread_cond_signal(&GC_suspend_ack_cv);
pthread_cond_wait(&GC_continue_cv, &GC_suspend_lock);
pthread_mutex_unlock(&GC_suspend_lock);
/* GC_printf1("Continuing 0x%x\n", pthread_self()); */
}
GC_bool GC_thr_initialized = FALSE;
size_t GC_min_stack_sz;
size_t GC_page_sz;
# define N_FREE_LISTS 25
ptr_t GC_stack_free_lists[N_FREE_LISTS] = { 0 };
/* GC_stack_free_lists[i] is free list for stacks of */
/* size GC_min_stack_sz*2**i. */
/* Free lists are linked through first word. */
/* Return a stack of size at least *stack_size. *stack_size is */
/* replaced by the actual stack size. */
/* Caller holds allocation lock. */
ptr_t GC_stack_alloc(size_t * stack_size)
{
register size_t requested_sz = *stack_size;
register size_t search_sz = GC_min_stack_sz;
register int index = 0; /* = log2(search_sz/GC_min_stack_sz) */
register ptr_t result;
while (search_sz < requested_sz) {
search_sz *= 2;
index++;
}
if ((result = GC_stack_free_lists[index]) == 0
&& (result = GC_stack_free_lists[index+1]) != 0) {
/* Try next size up. */
search_sz *= 2; index++;
}
if (result != 0) {
GC_stack_free_lists[index] = *(ptr_t *)result;
} else {
result = (ptr_t) GC_scratch_alloc(search_sz + 2*GC_page_sz);
result = (ptr_t)(((word)result + GC_page_sz) & ~(GC_page_sz - 1));
/* Protect hottest page to detect overflow. */
/* mprotect(result, GC_page_sz, PROT_NONE); */
result += GC_page_sz;
}
*stack_size = search_sz;
return(result);
}
/* Caller holds allocation lock. */
void GC_stack_free(ptr_t stack, size_t size)
{
register int index = 0;
register size_t search_sz = GC_min_stack_sz;
while (search_sz < size) {
search_sz *= 2;
index++;
}
if (search_sz != size) ABORT("Bad stack size");
*(ptr_t *)stack = GC_stack_free_lists[index];
GC_stack_free_lists[index] = stack;
}
# define THREAD_TABLE_SZ 128 /* Must be power of 2 */
volatile GC_thread GC_threads[THREAD_TABLE_SZ];
/* Add a thread to GC_threads. We assume it wasn't already there. */
/* Caller holds allocation lock. */
GC_thread GC_new_thread(pthread_t id)
{
int hv = ((word)id) % THREAD_TABLE_SZ;
GC_thread result;
static struct GC_Thread_Rep first_thread;
static GC_bool first_thread_used = FALSE;
if (!first_thread_used) {
result = &first_thread;
first_thread_used = TRUE;
/* Dont acquire allocation lock, since we may already hold it. */
} else {
result = (struct GC_Thread_Rep *)
GC_generic_malloc_inner(sizeof(struct GC_Thread_Rep), NORMAL);
}
if (result == 0) return(0);
result -> id = id;
result -> next = GC_threads[hv];
GC_threads[hv] = result;
/* result -> flags = 0; */
/* result -> stop = 0; */
return(result);
}
/* Delete a thread from GC_threads. We assume it is there. */
/* (The code intentionally traps if it wasn't.) */
/* Caller holds allocation lock. */
void GC_delete_thread(pthread_t id)
{
int hv = ((word)id) % THREAD_TABLE_SZ;
register GC_thread p = GC_threads[hv];
register GC_thread prev = 0;
while (!pthread_equal(p -> id, id)) {
prev = p;
p = p -> next;
}
if (prev == 0) {
GC_threads[hv] = p -> next;
} else {
prev -> next = p -> next;
}
}
/* If a thread has been joined, but we have not yet */
/* been notified, then there may be more than one thread */
/* in the table with the same pthread id. */
/* This is OK, but we need a way to delete a specific one. */
void GC_delete_gc_thread(pthread_t id, GC_thread gc_id)
{
int hv = ((word)id) % THREAD_TABLE_SZ;
register GC_thread p = GC_threads[hv];
register GC_thread prev = 0;
while (p != gc_id) {
prev = p;
p = p -> next;
}
if (prev == 0) {
GC_threads[hv] = p -> next;
} else {
prev -> next = p -> next;
}
}
/* Return a GC_thread corresponding to a given thread_t. */
/* Returns 0 if it's not there. */
/* Caller holds allocation lock or otherwise inhibits */
/* updates. */
/* If there is more than one thread with the given id we */
/* return the most recent one. */
GC_thread GC_lookup_thread(pthread_t id)
{
int hv = ((word)id) % THREAD_TABLE_SZ;
register GC_thread p = GC_threads[hv];
while (p != 0 && !pthread_equal(p -> id, id)) p = p -> next;
return(p);
}
/* Caller holds allocation lock. */
void GC_stop_world()
{
pthread_t my_thread = pthread_self();
register int i;
register GC_thread p;
register int result;
struct timespec timeout;
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (p -> id != my_thread) {
if (p -> flags & FINISHED) {
p -> stop = STOPPED;
continue;
}
p -> stop = PLEASE_STOP;
result = pthread_kill(p -> id, SIG_SUSPEND);
/* GC_printf1("Sent signal to 0x%x\n", p -> id); */
switch(result) {
case ESRCH:
/* Not really there anymore. Possible? */
p -> stop = STOPPED;
break;
case 0:
break;
default:
ABORT("pthread_kill failed");
}
}
}
}
pthread_mutex_lock(&GC_suspend_lock);
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
while (p -> id != my_thread && p -> stop != STOPPED) {
clock_gettime(CLOCK_REALTIME, &timeout);
timeout.tv_nsec += 50000000; /* 50 msecs */
if (timeout.tv_nsec >= 1000000000) {
timeout.tv_nsec -= 1000000000;
++timeout.tv_sec;
}
result = pthread_cond_timedwait(&GC_suspend_ack_cv,
&GC_suspend_lock,
&timeout);
if (result == ETIMEDOUT) {
/* Signal was lost or misdirected. Try again. */
/* Duplicate signals should be benign. */
result = pthread_kill(p -> id, SIG_SUSPEND);
}
}
}
}
pthread_mutex_unlock(&GC_suspend_lock);
/* GC_printf1("World stopped 0x%x\n", pthread_self()); */
}
/* Caller holds allocation lock. */
void GC_start_world()
{
GC_thread p;
unsigned i;
/* GC_printf0("World starting\n"); */
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
p -> stop = NOT_STOPPED;
}
}
pthread_mutex_lock(&GC_suspend_lock);
/* All other threads are at pthread_cond_wait in signal handler. */
/* Otherwise we couldn't have acquired the lock. */
pthread_mutex_unlock(&GC_suspend_lock);
pthread_cond_broadcast(&GC_continue_cv);
}
# ifdef MMAP_STACKS
--> not really supported yet.
int GC_is_thread_stack(ptr_t addr)
{
register int i;
register GC_thread p;
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (p -> stack_size != 0) {
if (p -> stack <= addr &&
addr < p -> stack + p -> stack_size)
return 1;
}
}
}
return 0;
}
# endif
/* We hold allocation lock. We assume the world is stopped. */
void GC_push_all_stacks()
{
register int i;
register GC_thread p;
register ptr_t sp = GC_approx_sp();
register ptr_t lo, hi;
pthread_t me = pthread_self();
if (!GC_thr_initialized) GC_thr_init();
/* GC_printf1("Pushing stacks from thread 0x%x\n", me); */
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (p -> flags & FINISHED) continue;
if (pthread_equal(p -> id, me)) {
lo = GC_approx_sp();
} else {
lo = p -> stack_ptr;
}
if (p -> stack_size != 0) {
hi = p -> stack + p -> stack_size;
} else {
/* The original stack. */
hi = GC_stackbottom;
}
GC_push_all_stack(lo, hi);
}
}
}
/* We hold the allocation lock. */
void GC_thr_init()
{
GC_thread t;
struct sigaction act;
if (GC_thr_initialized) return;
GC_thr_initialized = TRUE;
GC_min_stack_sz = HBLKSIZE;
GC_page_sz = sysconf(_SC_PAGESIZE);
(void) sigaction(SIG_SUSPEND, 0, &act);
if (act.sa_handler != SIG_DFL)
ABORT("Previously installed SIG_SUSPEND handler");
/* Install handler. */
act.sa_handler = GC_suspend_handler;
act.sa_flags = SA_RESTART;
(void) sigemptyset(&act.sa_mask);
if (0 != sigaction(SIG_SUSPEND, &act, 0))
ABORT("Failed to install SIG_SUSPEND handler");
/* Add the initial thread, so we can stop it. */
t = GC_new_thread(pthread_self());
t -> stack_size = 0;
t -> stack_ptr = (ptr_t)(&t);
t -> flags = DETACHED;
}
int GC_pthread_sigmask(int how, const sigset_t *set, sigset_t *oset)
{
sigset_t fudged_set;
if (set != NULL && (how == SIG_BLOCK || how == SIG_SETMASK)) {
fudged_set = *set;
sigdelset(&fudged_set, SIG_SUSPEND);
set = &fudged_set;
}
return(pthread_sigmask(how, set, oset));
}
struct start_info {
void *(*start_routine)(void *);
void *arg;
word flags;
ptr_t stack;
size_t stack_size;
sem_t registered; /* 1 ==> in our thread table, but */
/* parent hasn't yet noticed. */
};
void GC_thread_exit_proc(void *arg)
{
GC_thread me;
LOCK();
me = GC_lookup_thread(pthread_self());
if (me -> flags & DETACHED) {
GC_delete_thread(pthread_self());
} else {
me -> flags |= FINISHED;
}
UNLOCK();
}
int GC_pthread_join(pthread_t thread, void **retval)
{
int result;
GC_thread thread_gc_id;
LOCK();
thread_gc_id = GC_lookup_thread(thread);
/* This is guaranteed to be the intended one, since the thread id */
/* cant have been recycled by pthreads. */
UNLOCK();
result = pthread_join(thread, retval);
/* Some versions of the Irix pthreads library can erroneously */
/* return EINTR when the call succeeds. */
if (EINTR == result) result = 0;
LOCK();
/* Here the pthread thread id may have been recycled. */
GC_delete_gc_thread(thread, thread_gc_id);
UNLOCK();
return result;
}
void * GC_start_routine(void * arg)
{
struct start_info * si = arg;
void * result;
GC_thread me;
pthread_t my_pthread;
void *(*start)(void *);
void *start_arg;
my_pthread = pthread_self();
/* If a GC occurs before the thread is registered, that GC will */
/* ignore this thread. That's fine, since it will block trying to */
/* acquire the allocation lock, and won't yet hold interesting */
/* pointers. */
LOCK();
/* We register the thread here instead of in the parent, so that */
/* we don't need to hold the allocation lock during pthread_create. */
/* Holding the allocation lock there would make REDIRECT_MALLOC */
/* impossible. It probably still doesn't work, but we're a little */
/* closer ... */
/* This unfortunately means that we have to be careful the parent */
/* doesn't try to do a pthread_join before we're registered. */
me = GC_new_thread(my_pthread);
me -> flags = si -> flags;
me -> stack = si -> stack;
me -> stack_size = si -> stack_size;
me -> stack_ptr = (ptr_t)si -> stack + si -> stack_size - sizeof(word);
UNLOCK();
start = si -> start_routine;
start_arg = si -> arg;
sem_post(&(si -> registered));
pthread_cleanup_push(GC_thread_exit_proc, 0);
result = (*start)(start_arg);
me -> status = result;
me -> flags |= FINISHED;
pthread_cleanup_pop(1);
/* This involves acquiring the lock, ensuring that we can't exit */
/* while a collection that thinks we're alive is trying to stop */
/* us. */
return(result);
}
int
GC_pthread_create(pthread_t *new_thread,
const pthread_attr_t *attr,
void *(*start_routine)(void *), void *arg)
{
int result;
GC_thread t;
void * stack;
size_t stacksize;
pthread_attr_t new_attr;
int detachstate;
word my_flags = 0;
struct start_info * si = GC_malloc(sizeof(struct start_info));
/* This is otherwise saved only in an area mmapped by the thread */
/* library, which isn't visible to the collector. */
if (0 == si) return(ENOMEM);
sem_init(&(si -> registered), 0, 0);
si -> start_routine = start_routine;
si -> arg = arg;
LOCK();
if (!GC_thr_initialized) GC_thr_init();
if (NULL == attr) {
stack = 0;
(void) pthread_attr_init(&new_attr);
} else {
new_attr = *attr;
pthread_attr_getstackaddr(&new_attr, &stack);
}
pthread_attr_getstacksize(&new_attr, &stacksize);
pthread_attr_getdetachstate(&new_attr, &detachstate);
if (stacksize < GC_min_stack_sz) ABORT("Stack too small");
if (0 == stack) {
stack = (void *)GC_stack_alloc(&stacksize);
if (0 == stack) {
UNLOCK();
return(ENOMEM);
}
pthread_attr_setstackaddr(&new_attr, stack);
} else {
my_flags |= CLIENT_OWNS_STACK;
}
if (PTHREAD_CREATE_DETACHED == detachstate) my_flags |= DETACHED;
si -> flags = my_flags;
si -> stack = stack;
si -> stack_size = stacksize;
result = pthread_create(new_thread, &new_attr, GC_start_routine, si);
if (0 == new_thread && !(my_flags & CLIENT_OWNS_STACK)) {
GC_stack_free(stack, stacksize);
}
UNLOCK();
/* Wait until child has been added to the thread table. */
/* This also ensures that we hold onto si until the child is done */
/* with it. Thus it doesn't matter whether it is otherwise */
/* visible to the collector. */
if (0 != sem_wait(&(si -> registered))) ABORT("sem_wait failed");
sem_destroy(&(si -> registered));
/* pthread_attr_destroy(&new_attr); */
return(result);
}
GC_bool GC_collecting = 0; /* A hint that we're in the collector and */
/* holding the allocation lock for an */
/* extended period. */
/* Reasonably fast spin locks. Basically the same implementation */
/* as STL alloc.h. This isn't really the right way to do this. */
/* but until the POSIX scheduling mess gets straightened out ... */
unsigned long GC_allocate_lock = 0;
#define SLEEP_THRESHOLD 3
void GC_lock()
{
# define low_spin_max 30 /* spin cycles if we suspect uniprocessor */
# define high_spin_max 1000 /* spin cycles for multiprocessor */
static unsigned spin_max = low_spin_max;
unsigned my_spin_max;
static unsigned last_spins = 0;
unsigned my_last_spins;
volatile unsigned junk;
# define PAUSE junk *= junk; junk *= junk; junk *= junk; junk *= junk
int i;
if (!GC_test_and_set(&GC_allocate_lock, 1)) {
return;
}
junk = 0;
my_spin_max = spin_max;
my_last_spins = last_spins;
for (i = 0; i < my_spin_max; i++) {
if (GC_collecting) goto yield;
if (i < my_last_spins/2 || GC_allocate_lock) {
PAUSE;
continue;
}
if (!GC_test_and_set(&GC_allocate_lock, 1)) {
/*
* got it!
* Spinning worked. Thus we're probably not being scheduled
* against the other process with which we were contending.
* Thus it makes sense to spin longer the next time.
*/
last_spins = i;
spin_max = high_spin_max;
return;
}
}
/* We are probably being scheduled against the other process. Sleep. */
spin_max = low_spin_max;
yield:
for (i = 0;; ++i) {
if (!GC_test_and_set(&GC_allocate_lock, 1)) {
return;
}
if (i < SLEEP_THRESHOLD) {
sched_yield();
} else {
struct timespec ts;
if (i > 26) i = 26;
/* Don't wait for more than about 60msecs, even */
/* under extreme contention. */
ts.tv_sec = 0;
ts.tv_nsec = 1 << i;
nanosleep(&ts, 0);
}
}
}
# else
#ifndef LINT
int GC_no_Irix_threads;
#endif
# endif /* IRIX_THREADS */
