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WIP: tweaking locking of GC trace

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Justin Ethier 2018-06-12 15:54:51 -04:00
parent 74d53eb334
commit fa82aeb6a5
1 changed files with 13 additions and 5 deletions
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18
gc.c
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@ -1829,15 +1829,23 @@ void gc_collector_trace()
{ {
ck_array_iterator_t iterator; ck_array_iterator_t iterator;
gc_thread_data *m; gc_thread_data *m;
int clean = 0; int clean = 0, last_write;
while (!clean) { while (!clean) {
clean = 1; clean = 1;
CK_ARRAY_FOREACH(&Cyc_mutators, &iterator, &m) { CK_ARRAY_FOREACH(&Cyc_mutators, &iterator, &m) {
// TODO: ideally, want to use a lock-free data structure to prevent // TODO: ideally, want to use a lock-free data structure to prevent
// having to use a mutex here. see corresponding code in gc_mark_gray // having to use a mutex here. see corresponding code in gc_mark_gray
//pthread_mutex_lock(&(m->lock)); pthread_mutex_lock(&(m->lock));
while (m->last_read < m->last_write) { // JAE - try doing this loop (majority of tracing) without the lock.
// we shouldn't need to be locked to do it anyway and we still lock
// below as a fail-safe. One potential issue here, will we be broken
// if the mark buffer needs to be grown. I think not because we still
// will only go as far as the mutator already went with the version of
// last write we are holding here...
last_write = m->last_write;
pthread_mutex_unlock(&(m->lock));
while (m->last_read < last_write) {
clean = 0; clean = 0;
#if GC_DEBUG_VERBOSE #if GC_DEBUG_VERBOSE
fprintf(stderr, fprintf(stderr,
@ -1854,7 +1862,7 @@ void gc_collector_trace()
// mutator a chance to respond, to prevent exiting early. // mutator a chance to respond, to prevent exiting early.
// This is experimental, not sure if it is necessary // This is experimental, not sure if it is necessary
if (clean) { if (clean) {
//pthread_mutex_lock(&(m->lock)); pthread_mutex_lock(&(m->lock));
if (m->last_read < m->last_write) { if (m->last_read < m->last_write) {
#if GC_SAFETY_CHECKS #if GC_SAFETY_CHECKS
fprintf(stderr, fprintf(stderr,
@ -1864,7 +1872,7 @@ void gc_collector_trace()
} else if (m->pending_writes) { } else if (m->pending_writes) {
clean = 0; clean = 0;
} }
//pthread_mutex_unlock(&(m->lock)); pthread_mutex_unlock(&(m->lock));
} }
} }
} }