/* Adds a chunk of work to another thread's in-tray. */
static void push_work_to_thread_in_tray(MVMThreadContext *tc, MVMuint32 target, MVMGCPassedWork *work) {
MVMGCPassedWork * volatile *target_tray;
/* Locate the thread to pass the work to. */
MVMThreadContext *target_tc = NULL;
if (target == 1) {
/* It's going to the main thread. */
target_tc = tc->instance->main_thread;
}
else {
MVMThread *t = (MVMThread *)MVM_load(&tc->instance->threads);
do {
if (t->body.tc && t->body.tc->thread_id == target) {
target_tc = t->body.tc;
break;
}
} while ((t = t->body.next));
if (!target_tc)
MVM_panic(MVM_exitcode_gcnursery, "Internal error: invalid thread ID %d in GC work pass", target);
}
/* Pass the work, chaining any other in-tray entries for the thread
* after us. */
target_tray = &target_tc->gc_in_tray;
while (1) {
MVMGCPassedWork *orig = *target_tray;
work->next = orig;
if (MVM_casptr(target_tray, orig, work) == orig)
return;
}
}
/* Does work in a thread's in-tray, if any. Returns a non-zero value if work
* was found and done, and zero otherwise. */
static int process_in_tray(MVMThreadContext *tc, MVMuint8 gen) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Considering extra work\n");
if (MVM_load(&tc->gc_in_tray)) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : Was given extra work by another thread; doing it\n");
MVM_gc_collect(tc, MVMGCWhatToDo_InTray, gen);
return 1;
}
return 0;
}
/* Adds a chunk of work to another thread's in-tray. */
static void push_work_to_thread_in_tray(MVMThreadContext *tc, MVMuint32 target, MVMGCPassedWork *work) {
MVMint32 j;
MVMGCPassedWork * volatile *target_tray;
/* Locate the thread to pass the work to. */
MVMThreadContext *target_tc = NULL;
if (target == 0) {
/* It's going to the main thread. */
target_tc = tc->instance->main_thread;
}
else {
MVMThread *t = (MVMThread *)MVM_load(&tc->instance->threads);
do {
if (t->body.tc->thread_id == target) {
target_tc = t->body.tc;
break;
}
} while ((t = t->body.next));
if (!target_tc)
MVM_panic(MVM_exitcode_gcnursery, "Internal error: invalid thread ID in GC work pass");
}
/* push to sent_items list */
if (tc->gc_sent_items) {
tc->gc_sent_items->next_by_sender = work;
work->last_by_sender = tc->gc_sent_items;
}
/* queue it up to check if the check list isn't clear */
if (!MVM_load(&tc->gc_next_to_check)) {
MVM_store(&tc->gc_next_to_check, work);
}
tc->gc_sent_items = work;
/* Pass the work, chaining any other in-tray entries for the thread
* after us. */
target_tray = &target_tc->gc_in_tray;
while (1) {
MVMGCPassedWork *orig = *target_tray;
work->next = orig;
if (MVM_casptr(target_tray, orig, work) == orig)
return;
}
}
/* Called by a thread when it thinks it is done with GC. It may get some more
* work yet, though. */
static void clear_intrays(MVMThreadContext *tc, MVMuint8 gen) {
MVMuint32 did_work = 1;
while (did_work) {
MVMThread *cur_thread;
did_work = 0;
cur_thread = (MVMThread *)MVM_load(&tc->instance->threads);
while (cur_thread) {
if (cur_thread->body.tc)
did_work += process_in_tray(cur_thread->body.tc, gen);
cur_thread = cur_thread->body.next;
}
}
}
void MVM_finalize_walk_queues(MVMThreadContext *tc, MVMuint8 gen) {
MVMThread *cur_thread = (MVMThread *)MVM_load(&tc->instance->threads);
while (cur_thread) {
if (cur_thread->body.tc) {
walk_thread_finalize_queue(cur_thread->body.tc, gen);
if (cur_thread->body.tc->num_finalizing > 0) {
MVM_gc_collect(cur_thread->body.tc, MVMGCWhatToDo_Finalizing, gen);
setup_finalize_handler_call(cur_thread->body.tc);
}
}
cur_thread = cur_thread->body.next;
}
}
/* This is called when a thread hits an interrupt at a GC safe point. This means
* that another thread is already trying to start a GC run, so we don't need to
* try and do that, just enlist in the run. */
void MVM_gc_enter_from_interrupt(MVMThreadContext *tc) {
AO_t curr;
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Entered from interrupt\n");
MVM_telemetry_timestamp(tc, "gc_enter_from_interrupt");
/* If profiling, record that GC is starting. */
if (tc->instance->profiling)
MVM_profiler_log_gc_start(tc, is_full_collection(tc));
/* We'll certainly take care of our own work. */
tc->gc_work_count = 0;
add_work(tc, tc);
/* Indicate that we're ready to GC. Only want to decrement it if it's 2 or
* greater (0 should never happen; 1 means the coordinator is still counting
* up how many threads will join in, so we should wait until it decides to
* decrement.) */
while ((curr = MVM_load(&tc->instance->gc_start)) < 2
|| !MVM_trycas(&tc->instance->gc_start, curr, curr - 1)) {
/* MVM_platform_thread_yield();*/
}
/* Wait for all threads to indicate readiness to collect. */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Waiting for other threads\n");
while (MVM_load(&tc->instance->gc_start)) {
/* MVM_platform_thread_yield();*/
}
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Entering run_gc\n");
run_gc(tc, MVMGCWhatToDo_NoInstance);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : GC complete\n");
/* If profiling, record that GC is over. */
if (tc->instance->profiling)
MVM_profiler_log_gc_end(tc);
}
/* Decreases the reference count of a frame. If it hits zero, then we can
* free it. Returns null for convenience. */
MVMFrame * MVM_frame_dec_ref(MVMThreadContext *tc, MVMFrame *frame) {
/* MVM_dec returns what the count was before it decremented it
* to zero, so we look for 1 here. */
while (MVM_decr(&frame->ref_count) == 1) {
MVMuint32 pool_index = frame->static_info->body.pool_index;
MVMFrame *node = tc->frame_pool_table[pool_index];
MVMFrame *outer_to_decr = frame->outer;
/* If there's a caller pointer, decrement that. */
if (frame->caller)
frame->caller = MVM_frame_dec_ref(tc, frame->caller);
if (node && MVM_load(&node->ref_count) >= MVMFramePoolLengthLimit) {
/* There's no room on the free list, so destruction.*/
if (frame->env) {
free(frame->env);
frame->env = NULL;
}
if (frame->work) {
MVM_args_proc_cleanup(tc, &frame->params);
free(frame->work);
frame->work = NULL;
}
free(frame);
}
else { /* Unshift it to the free list */
MVM_store(&frame->ref_count, (frame->outer = node) ? MVM_load(&node->ref_count) + 1 : 1);
tc->frame_pool_table[pool_index] = frame;
}
if (outer_to_decr)
frame = outer_to_decr; /* and loop */
else
break;
}
return NULL;
}
/* Called by a thread to indicate it is about to enter a blocking operation.
* This tells any thread that is coordinating a GC run that this thread will
* be unable to participate. */
void MVM_gc_mark_thread_blocked(MVMThreadContext *tc) {
/* This may need more than one attempt. */
while (1) {
/* Try to set it from running to unable - the common case. */
if (MVM_cas(&tc->gc_status, MVMGCStatus_NONE,
MVMGCStatus_UNABLE) == MVMGCStatus_NONE)
return;
/* The only way this can fail is if another thread just decided we're to
* participate in a GC run. */
if (MVM_load(&tc->gc_status) == MVMGCStatus_INTERRUPT)
MVM_gc_enter_from_interrupt(tc);
else
MVM_panic(MVM_exitcode_gcorch, "Invalid GC status observed; aborting");
}
}
static MVMint32 is_full_collection(MVMThreadContext *tc) {
MVMuint64 percent_growth, promoted;
size_t rss;
/* If it's below the absolute minimum, quickly return. */
promoted = (MVMuint64)MVM_load(&tc->instance->gc_promoted_bytes_since_last_full);
if (promoted < MVM_GC_GEN2_THRESHOLD_MINIMUM)
return 0;
/* If we're heap profiling then don't consider the resident set size, as
* it will be hugely distorted by the profile data we record. */
if (MVM_profile_heap_profiling(tc))
return 1;
/* Otherwise, consider percentage of resident set size. */
if (uv_resident_set_memory(&rss) < 0 || rss == 0)
rss = 50 * 1024 * 1024;
percent_growth = (100 * promoted) / (MVMuint64)rss;
return percent_growth >= MVM_GC_GEN2_THRESHOLD_PERCENT;
}
static MVMuint32 signal_all_but(MVMThreadContext *tc, MVMThread *t, MVMThread *tail) {
MVMuint32 count = 0;
MVMThread *next;
if (!t) {
return 0;
}
do {
next = t->body.next;
switch (MVM_load(&t->body.stage)) {
case MVM_thread_stage_starting:
case MVM_thread_stage_waiting:
case MVM_thread_stage_started:
if (t->body.tc != tc) {
count += signal_one_thread(tc, t->body.tc);
}
break;
case MVM_thread_stage_exited:
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : queueing to clear nursery of thread %d\n", t->body.tc->thread_id);
add_work(tc, t->body.tc);
break;
case MVM_thread_stage_clearing_nursery:
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : queueing to destroy thread %d\n", t->body.tc->thread_id);
/* last GC run for this thread */
add_work(tc, t->body.tc);
break;
case MVM_thread_stage_destroyed:
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : found a destroyed thread\n");
/* will be cleaned up (removed from the lists) shortly */
break;
default:
MVM_panic(MVM_exitcode_gcorch, "Corrupted MVMThread or running threads list: invalid thread stage %"MVM_PRSz"", MVM_load(&t->body.stage));
}
} while (next && (t = next));
if (tail)
MVM_gc_write_barrier(tc, (MVMCollectable *)t, (MVMCollectable *)tail);
t->body.next = tail;
return count;
}
/* Goes through all threads but the current one and notifies them that a
* GC run is starting. Those that are blocked are considered excluded from
* the run, and are not counted. Returns the count of threads that should be
* added to the finished countdown. */
static MVMuint32 signal_one_thread(MVMThreadContext *tc, MVMThreadContext *to_signal) {
/* Loop here since we may not succeed first time (e.g. the status of the
* thread may change between the two ways we try to twiddle it). */
while (1) {
switch (MVM_load(&to_signal->gc_status)) {
case MVMGCStatus_NONE:
/* Try to set it from running to interrupted - the common case. */
if (MVM_cas(&to_signal->gc_status, MVMGCStatus_NONE,
MVMGCStatus_INTERRUPT) == MVMGCStatus_NONE) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Signalled thread %d to interrupt\n", to_signal->thread_id);
return 1;
}
break;
case MVMGCStatus_INTERRUPT:
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : thread %d already interrupted\n", to_signal->thread_id);
return 0;
case MVMGCStatus_UNABLE:
/* Otherwise, it's blocked; try to set it to work Stolen. */
if (MVM_cas(&to_signal->gc_status, MVMGCStatus_UNABLE,
MVMGCStatus_STOLEN) == MVMGCStatus_UNABLE) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : A blocked thread %d spotted; work stolen\n", to_signal->thread_id);
add_work(tc, to_signal);
return 0;
}
break;
/* this case occurs if a child thread is Stolen by its parent
* before we get to it in the chain. */
case MVMGCStatus_STOLEN:
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : thread %d already stolen (it was a spawning child)\n", to_signal->thread_id);
return 0;
default:
MVM_panic(MVM_exitcode_gcorch, "invalid status %"MVM_PRSz" in GC orchestrate\n", MVM_load(&to_signal->gc_status));
return 0;
}
}
}
/* This is called when the allocator finds it has run out of memory and wants
* to trigger a GC run. In this case, it's possible (probable, really) that it
* will need to do that triggering, notifying other running threads that the
* time has come to GC. */
void MVM_gc_enter_from_allocator(MVMThreadContext *tc) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Entered from allocate\n");
/* Try to start the GC run. */
if (MVM_trycas(&tc->instance->gc_start, 0, 1)) {
MVMThread *last_starter = NULL;
MVMuint32 num_threads = 0;
MVMuint32 is_full;
/* Need to wait for other threads to reset their gc_status. */
while (MVM_load(&tc->instance->gc_ack)) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : waiting for other thread's gc_ack\n");
MVM_platform_thread_yield();
}
/* We are the winner of the GC starting race. This gives us some
* extra responsibilities as well as doing the usual things.
* First, increment GC sequence number. */
MVM_incr(&tc->instance->gc_seq_number);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : GC thread elected coordinator: starting gc seq %d\n",
(int)MVM_load(&tc->instance->gc_seq_number));
/* Decide if it will be a full collection. */
is_full = is_full_collection(tc);
/* If profiling, record that GC is starting. */
if (tc->instance->profiling)
MVM_profiler_log_gc_start(tc, is_full);
/* Ensure our stolen list is empty. */
tc->gc_work_count = 0;
/* Flag that we didn't agree on this run that all the in-trays are
* cleared (a responsibility of the co-ordinator. */
MVM_store(&tc->instance->gc_intrays_clearing, 1);
/* We'll take care of our own work. */
add_work(tc, tc);
/* Find other threads, and signal or steal. */
do {
MVMThread *threads = (MVMThread *)MVM_load(&tc->instance->threads);
if (threads && threads != last_starter) {
MVMThread *head = threads;
MVMuint32 add;
while ((threads = (MVMThread *)MVM_casptr(&tc->instance->threads, head, NULL)) != head) {
head = threads;
}
add = signal_all_but(tc, head, last_starter);
last_starter = head;
if (add) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Found %d other threads\n", add);
MVM_add(&tc->instance->gc_start, add);
num_threads += add;
}
}
/* If there's an event loop thread, wake it up to participate. */
if (tc->instance->event_loop_wakeup)
uv_async_send(tc->instance->event_loop_wakeup);
} while (MVM_load(&tc->instance->gc_start) > 1);
/* Sanity checks. */
if (!MVM_trycas(&tc->instance->threads, NULL, last_starter))
MVM_panic(MVM_exitcode_gcorch, "threads list corrupted\n");
if (MVM_load(&tc->instance->gc_finish) != 0)
MVM_panic(MVM_exitcode_gcorch, "Finish votes was %"MVM_PRSz"\n", MVM_load(&tc->instance->gc_finish));
/* gc_ack gets an extra so the final acknowledger
* can also free the STables. */
MVM_store(&tc->instance->gc_finish, num_threads + 1);
MVM_store(&tc->instance->gc_ack, num_threads + 2);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : finish votes is %d\n",
(int)MVM_load(&tc->instance->gc_finish));
/* Now we're ready to start, zero promoted since last full collection
* counter if this is a full collect. */
if (is_full)
MVM_store(&tc->instance->gc_promoted_bytes_since_last_full, 0);
/* Signal to the rest to start */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : coordinator signalling start\n");
if (MVM_decr(&tc->instance->gc_start) != 1)
MVM_panic(MVM_exitcode_gcorch, "Start votes was %"MVM_PRSz"\n", MVM_load(&tc->instance->gc_start));
/* Start collecting. */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : coordinator entering run_gc\n");
run_gc(tc, MVMGCWhatToDo_All);
/* Free any STables that have been marked for deletion. It's okay for
* us to muck around in another thread's fromspace while it's mutating
* tospace, really. */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Freeing STables if needed\n");
MVM_gc_collect_free_stables(tc);
/* If profiling, record that GC is over. */
if (tc->instance->profiling)
MVM_profiler_log_gc_end(tc);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : GC complete (cooridnator)\n");
}
else {
/* Another thread beat us to starting the GC sync process. Thus, act as
* if we were interrupted to GC. */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Lost coordinator election\n");
MVM_gc_enter_from_interrupt(tc);
}
}
static MVMint32 is_full_collection(MVMThreadContext *tc) {
MVMuint64 threshold = MVM_GC_GEN2_THRESHOLD_BASE +
(tc->instance->num_user_threads * MVM_GC_GEN2_THRESHOLD_THREAD);
return MVM_load(&tc->instance->gc_promoted_bytes_since_last_full) > threshold;
}
static void finish_gc(MVMThreadContext *tc, MVMuint8 gen, MVMuint8 is_coordinator) {
MVMuint32 i, did_work;
/* Do any extra work that we have been passed. */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : doing any work in thread in-trays\n");
did_work = 1;
while (did_work) {
did_work = 0;
for (i = 0; i < tc->gc_work_count; i++)
did_work += process_in_tray(tc->gc_work[i].tc, gen);
}
/* Decrement gc_finish to say we're done, and wait for termination. */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Voting to finish\n");
MVM_decr(&tc->instance->gc_finish);
while (MVM_load(&tc->instance->gc_finish)) {
for (i = 0; i < 1000; i++)
; /* XXX Something HT-efficienter. */
/* XXX Here we can look to see if we got passed any work, and if so
* try to un-vote. */
}
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Termination agreed\n");
/* Co-ordinator should do final check over all the in-trays, and trigger
* collection until all is settled. Rest should wait. Additionally, after
* in-trays are settled, coordinator walks threads looking for anything
* that needs adding to the finalize queue. It then will make another
* iteration over in-trays to handle cross-thread references to objects
* needing finalization. For full collections, collected objects are then
* cleaned from all inter-generational sets, and finally any objects to
* be freed at the fixed size allocator's next safepoint are freed. */
if (is_coordinator) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : Co-ordinator handling in-tray clearing completion\n");
clear_intrays(tc, gen);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : Co-ordinator handling finalizers\n");
MVM_finalize_walk_queues(tc, gen);
clear_intrays(tc, gen);
if (gen == MVMGCGenerations_Both) {
MVMThread *cur_thread = (MVMThread *)MVM_load(&tc->instance->threads);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : Co-ordinator handling inter-gen root cleanup\n");
while (cur_thread) {
if (cur_thread->body.tc)
MVM_gc_root_gen2_cleanup(cur_thread->body.tc);
cur_thread = cur_thread->body.next;
}
}
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : Co-ordinator handling fixed-size allocator safepoint frees\n");
MVM_fixed_size_safepoint(tc, tc->instance->fsa);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : Co-ordinator signalling in-trays clear\n");
MVM_store(&tc->instance->gc_intrays_clearing, 0);
}
else {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : Waiting for in-tray clearing completion\n");
while (MVM_load(&tc->instance->gc_intrays_clearing))
for (i = 0; i < 1000; i++)
; /* XXX Something HT-efficienter. */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : Got in-tray clearing complete notice\n");
}
/* Reset GC status flags. This is also where thread destruction happens,
* and it needs to happen before we acknowledge this GC run is finished. */
for (i = 0; i < tc->gc_work_count; i++) {
MVMThreadContext *other = tc->gc_work[i].tc;
MVMThread *thread_obj = other->thread_obj;
if (MVM_load(&thread_obj->body.stage) == MVM_thread_stage_clearing_nursery) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : transferring gen2 of thread %d\n", other->thread_id);
MVM_gc_gen2_transfer(other, tc);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : destroying thread %d\n", other->thread_id);
MVM_tc_destroy(other);
tc->gc_work[i].tc = thread_obj->body.tc = NULL;
MVM_store(&thread_obj->body.stage, MVM_thread_stage_destroyed);
}
else {
if (MVM_load(&thread_obj->body.stage) == MVM_thread_stage_exited) {
/* Don't bother freeing gen2; we'll do it next time */
MVM_store(&thread_obj->body.stage, MVM_thread_stage_clearing_nursery);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : set thread %d clearing nursery stage to %d\n",
other->thread_id, (int)MVM_load(&thread_obj->body.stage));
}
MVM_cas(&other->gc_status, MVMGCStatus_STOLEN, MVMGCStatus_UNABLE);
MVM_cas(&other->gc_status, MVMGCStatus_INTERRUPT, MVMGCStatus_NONE);
}
}
/* Signal acknowledgement of completing the cleanup,
* except for STables, and if we're the final to do
* so, free the STables, which have been linked. */
if (MVM_decr(&tc->instance->gc_ack) == 2) {
/* Set it to zero (we're guaranteed the only ones trying to write to
* it here). Actual STable free in MVM_gc_enter_from_allocator. */
MVM_store(&tc->instance->gc_ack, 0);
}
}
/* Checks if a thread has marked itself as blocked. Considers that the GC may
* have stolen its work and marked it as such also. So what this really
* answers is, "did this thread mark itself blocked, and since then not mark
* itself unblocked", which is useful if you need to conditionally unblock
* or re-block. If the status changes from blocked to stolen or stolen to
* blocked between checking this and calling unblock, it's safe anyway since
* these cases are handled in MVM_gc_mark_thread_unblocked. Note that this
* relies on a thread itself only ever calling block/unblock. */
MVMint32 MVM_gc_is_thread_blocked(MVMThreadContext *tc) {
AO_t gc_status = MVM_load(&(tc->gc_status));
return gc_status == MVMGCStatus_UNABLE ||
gc_status == MVMGCStatus_STOLEN;
}
/* Goes through the unmarked objects in the second generation heap and builds
* free lists out of them. Also does any required finalization. */
void MVM_gc_collect_free_gen2_unmarked(MVMThreadContext *tc) {
/* Visit each of the size class bins. */
MVMGen2Allocator *gen2 = tc->gen2;
MVMuint32 bin, obj_size, page, i;
char ***freelist_insert_pos;
for (bin = 0; bin < MVM_GEN2_BINS; bin++) {
/* If we've nothing allocated in this size class, skip it. */
if (gen2->size_classes[bin].pages == NULL)
continue;
/* Calculate object size for this bin. */
obj_size = (bin + 1) << MVM_GEN2_BIN_BITS;
/* freelist_insert_pos is a pointer to a memory location that
* stores the address of the last traversed free list node (char **). */
/* Initialize freelist insertion position to free list head. */
freelist_insert_pos = &gen2->size_classes[bin].free_list;
/* Visit each page. */
for (page = 0; page < gen2->size_classes[bin].num_pages; page++) {
/* Visit all the objects, looking for dead ones and reset the
* mark for each of them. */
char *cur_ptr = gen2->size_classes[bin].pages[page];
char *end_ptr = page + 1 == gen2->size_classes[bin].num_pages
? gen2->size_classes[bin].alloc_pos
: cur_ptr + obj_size * MVM_GEN2_PAGE_ITEMS;
char **last_insert_pos = NULL;
while (cur_ptr < end_ptr) {
MVMCollectable *col = (MVMCollectable *)cur_ptr;
/* Is this already a free list slot? If so, it becomes the
* new free list insert position. */
if (*freelist_insert_pos == (char **)cur_ptr) {
freelist_insert_pos = (char ***)cur_ptr;
}
/* Otherwise, it must be a collectable of some kind. Is it
* live? */
else if (col->forwarder) {
/* Yes; clear the mark. */
col->forwarder = NULL;
}
else {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_COLLECT, "Thread %d run %d : collecting an object %p in the gen2\n", col);
/* No, it's dead. Do any cleanup. */
if (!(col->flags & (MVM_CF_TYPE_OBJECT | MVM_CF_STABLE))) {
/* Object instance; call gc_free if needed. */
MVMObject *obj = (MVMObject *)col;
if (REPR(obj)->gc_free)
REPR(obj)->gc_free(tc, obj);
}
else if (col->flags & MVM_CF_TYPE_OBJECT) {
/* Type object; doesn't have anything extra that needs freeing. */
}
else if (col->flags & MVM_CF_STABLE) {
if (col->sc == (MVMSerializationContext *)1) {
/* We marked it dead last time, kill it. */
MVM_6model_stable_gc_free(tc, (MVMSTable *)col);
}
else {
if (MVM_load(&tc->gc_status) == MVMGCStatus_NONE) {
/* We're in global destruction, so enqueue to the end
* like we do in the nursery */
MVM_gc_collect_enqueue_stable_for_deletion(tc, (MVMSTable *)col);
} else {
/* There will definitely be another gc run, so mark it as "died last time". */
col->sc = (MVMSerializationContext *)1;
}
/* Skip the freelist updating. */
cur_ptr += obj_size;
continue;
}
}
else {
printf("item flags: %d\n", col->flags);
MVM_panic(MVM_exitcode_gcnursery, "Internal error: impossible case encountered in gen2 GC free");
}
/* Chain in to the free list. */
*((char **)cur_ptr) = (char *)*freelist_insert_pos;
*freelist_insert_pos = (char **)cur_ptr;
/* Update the pointer to the insert position to point to us */
freelist_insert_pos = (char ***)cur_ptr;
}
/* Move to the next object. */
cur_ptr += obj_size;
}
}
}
/* Also need to consider overflows. */
for (i = 0; i < gen2->num_overflows; i++) {
if (gen2->overflows[i]) {
MVMCollectable *col = gen2->overflows[i];
if (col->forwarder) {
/* A living over-sized object; just clear the mark. */
col->forwarder = NULL;
}
else {
/* Dead over-sized object. We know if it's this big it cannot
* be a type object or STable, so only need handle the simple
* object case. */
if (!(col->flags & (MVM_CF_TYPE_OBJECT | MVM_CF_STABLE))) {
MVMObject *obj = (MVMObject *)col;
if (REPR(obj)->gc_free)
REPR(obj)->gc_free(tc, obj);
}
else {
MVM_panic(MVM_exitcode_gcnursery, "Internal error: gen2 overflow contains non-object");
}
free(col);
gen2->overflows[i] = NULL;
}
}
}
}
