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Use atomics to access thd->gc_status

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Justin Ethier 2015-12-22 22:57:28 -05:00
parent 9a9b3cc640
commit ec8821b9ef
1 changed files with 18 additions and 9 deletions
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27
gc.c
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@ -771,7 +771,7 @@ void gc_mut_update(gc_thread_data *thd, object old_obj, object value)
{ {
int status = ATOMIC_GET(&gc_status_col), int status = ATOMIC_GET(&gc_status_col),
stage = ATOMIC_GET(&gc_stage); stage = ATOMIC_GET(&gc_stage);
if (thd->gc_status != STATUS_ASYNC) { if (ATOMIC_GET(&(thd->gc_status)) != STATUS_ASYNC) {
//fprintf(stderr, "DEBUG - GC sync marking heap obj %p ", old_obj); //fprintf(stderr, "DEBUG - GC sync marking heap obj %p ", old_obj);
//Cyc_display(old_obj, stderr); //Cyc_display(old_obj, stderr);
//fprintf(stderr, " and new value %p ", value); //fprintf(stderr, " and new value %p ", value);
@ -836,7 +836,7 @@ void gc_mut_update(gc_thread_data *thd, object old_obj, object value)
// TODO: still need to handle case where a mutator is blocked // TODO: still need to handle case where a mutator is blocked
void gc_mut_cooperate(gc_thread_data *thd, int buf_len) void gc_mut_cooperate(gc_thread_data *thd, int buf_len)
{ {
int i, status; int i, status_c, status_m;
#if GC_DEBUG_VERBOSE #if GC_DEBUG_VERBOSE
int debug_print = 0; int debug_print = 0;
#endif #endif
@ -847,9 +847,16 @@ void gc_mut_cooperate(gc_thread_data *thd, int buf_len)
thd->pending_writes = 0; thd->pending_writes = 0;
pthread_mutex_unlock(&(thd->lock)); pthread_mutex_unlock(&(thd->lock));
status = ATOMIC_GET(&gc_status_col); // TODO: I think below is thread safe, but this code is tricky.
if (thd->gc_status != status) { // worst case should be that some work is done twice if there is
if (thd->gc_status == STATUS_ASYNC) { // a race condition
//
// TODO: should use an atomic comparison here
status_c = ATOMIC_GET(&gc_status_col);
status_m = ATOMIC_GET(&(thd->gc_status));
if (status_m != status_c) {
ATOMIC_SET_IF_EQ(&(thd->gc_status), status_m, status_c);
if (status_m == STATUS_ASYNC) {
// Async is done, so clean up old mark data from the last collection // Async is done, so clean up old mark data from the last collection
pthread_mutex_lock(&(thd->lock)); pthread_mutex_lock(&(thd->lock));
thd->last_write = 0; thd->last_write = 0;
@ -857,7 +864,7 @@ void gc_mut_cooperate(gc_thread_data *thd, int buf_len)
thd->pending_writes = 0; thd->pending_writes = 0;
pthread_mutex_unlock(&(thd->lock)); pthread_mutex_unlock(&(thd->lock));
} }
else if (thd->gc_status == STATUS_SYNC2) { else if (status_m == STATUS_SYNC2) {
#if GC_DEBUG_VERBOSE #if GC_DEBUG_VERBOSE
debug_print = 1; debug_print = 1;
#endif #endif
@ -876,7 +883,6 @@ void gc_mut_cooperate(gc_thread_data *thd, int buf_len)
pthread_mutex_unlock(&(thd->lock)); pthread_mutex_unlock(&(thd->lock));
thd->gc_alloc_color = ATOMIC_GET(&gc_color_mark); thd->gc_alloc_color = ATOMIC_GET(&gc_color_mark);
} }
thd->gc_status = status;
} }
#if GC_DEBUG_VERBOSE #if GC_DEBUG_VERBOSE
if (debug_print) { if (debug_print) {
@ -1141,15 +1147,18 @@ void gc_wait_handshake()
CK_ARRAY_FOREACH(&Cyc_mutators, &iterator, &m) { CK_ARRAY_FOREACH(&Cyc_mutators, &iterator, &m) {
while (1) { while (1) {
// TODO: use an atomic comparison
statusc = ATOMIC_GET(&gc_status_col); statusc = ATOMIC_GET(&gc_status_col);
statusm = ATOMIC_GET(&(m->gc_status)); statusm = ATOMIC_GET(&(m->gc_status));
thread_status = ATOMIC_GET(&(m->thread_state));
if (statusc == statusm) { if (statusc == statusm) {
// Handshake succeeded, check next mutator // Handshake succeeded, check next mutator
break; break;
} }
if (thread_status == CYC_THREAD_STATE_TERMINATED) { thread_status = ATOMIC_GET(&(m->thread_state));
if (thread_status == CYC_THREAD_STATE_BLOCKED) {
// CAS
} else if (thread_status == CYC_THREAD_STATE_TERMINATED) {
// Thread is no longer running // Thread is no longer running
break; break;
} }