+#if defined(THREADED_RTS)
+ gc_running_threads = 0;
+#endif
+}
+
+static void
+wakeup_gc_threads (nat me USED_IF_THREADS)
+{
+#if defined(THREADED_RTS)
+ nat i;
+
+ if (n_gc_threads == 1) return;
+
+ for (i=0; i < n_gc_threads; i++) {
+ if (i == me) continue;
+ inc_running();
+ debugTrace(DEBUG_gc, "waking up gc thread %d", i);
+ if (gc_threads[i]->wakeup != GC_THREAD_STANDING_BY) barf("wakeup_gc_threads");
+
+ gc_threads[i]->wakeup = GC_THREAD_RUNNING;
+ ACQUIRE_SPIN_LOCK(&gc_threads[i]->mut_spin);
+ RELEASE_SPIN_LOCK(&gc_threads[i]->gc_spin);
+ }
+#endif
+}
+
+// After GC is complete, we must wait for all GC threads to enter the
+// standby state, otherwise they may still be executing inside
+// any_work(), and may even remain awake until the next GC starts.
+static void
+shutdown_gc_threads (nat me USED_IF_THREADS)
+{
+#if defined(THREADED_RTS)
+ nat i;
+
+ if (n_gc_threads == 1) return;
+
+ for (i=0; i < n_gc_threads; i++) {
+ if (i == me) continue;
+ while (gc_threads[i]->wakeup != GC_THREAD_WAITING_TO_CONTINUE) { write_barrier(); }
+ }
+#endif
+}
+
+#if defined(THREADED_RTS)
+void
+releaseGCThreads (Capability *cap USED_IF_THREADS)
+{
+ const nat n_threads = RtsFlags.ParFlags.nNodes;
+ const nat me = cap->no;
+ nat i;
+ for (i=0; i < n_threads; i++) {
+ if (i == me) continue;
+ if (gc_threads[i]->wakeup != GC_THREAD_WAITING_TO_CONTINUE)
+ barf("releaseGCThreads");
+
+ gc_threads[i]->wakeup = GC_THREAD_INACTIVE;
+ ACQUIRE_SPIN_LOCK(&gc_threads[i]->gc_spin);
+ RELEASE_SPIN_LOCK(&gc_threads[i]->mut_spin);
+ }
+}
+#endif
+
+/* ----------------------------------------------------------------------------
+ Initialise a generation that is to be collected
+ ------------------------------------------------------------------------- */
+
+static void
+prepare_collected_gen (generation *gen)
+{
+ nat i, g, n;
+ gen_workspace *ws;
+ bdescr *bd, *next;
+
+ // Throw away the current mutable list. Invariant: the mutable
+ // list always has at least one block; this means we can avoid a
+ // check for NULL in recordMutable().
+ g = gen->no;
+ if (g != 0) {
+ for (i = 0; i < n_capabilities; i++) {
+ freeChain(capabilities[i].mut_lists[g]);
+ capabilities[i].mut_lists[g] = allocBlock();
+ }
+ }
+
+ gen = &generations[g];
+ ASSERT(gen->no == g);
+
+ // we'll construct a new list of threads in this step
+ // during GC, throw away the current list.
+ gen->old_threads = gen->threads;
+ gen->threads = END_TSO_QUEUE;
+
+ // deprecate the existing blocks
+ gen->old_blocks = gen->blocks;
+ gen->n_old_blocks = gen->n_blocks;
+ gen->blocks = NULL;
+ gen->n_blocks = 0;
+ gen->n_words = 0;
+ gen->live_estimate = 0;
+
+ // initialise the large object queues.
+ ASSERT(gen->scavenged_large_objects == NULL);
+ ASSERT(gen->n_scavenged_large_blocks == 0);
+
+ // grab all the partial blocks stashed in the gc_thread workspaces and
+ // move them to the old_blocks list of this gen.
+ for (n = 0; n < n_capabilities; n++) {
+ ws = &gc_threads[n]->gens[gen->no];
+
+ for (bd = ws->part_list; bd != NULL; bd = next) {
+ next = bd->link;
+ bd->link = gen->old_blocks;
+ gen->old_blocks = bd;
+ gen->n_old_blocks += bd->blocks;
+ }
+ ws->part_list = NULL;
+ ws->n_part_blocks = 0;
+
+ ASSERT(ws->scavd_list == NULL);
+ ASSERT(ws->n_scavd_blocks == 0);
+
+ if (ws->todo_free != ws->todo_bd->start) {
+ ws->todo_bd->free = ws->todo_free;
+ ws->todo_bd->link = gen->old_blocks;
+ gen->old_blocks = ws->todo_bd;
+ gen->n_old_blocks += ws->todo_bd->blocks;
+ alloc_todo_block(ws,0); // always has one block.
+ }
+ }
+
+ // mark the small objects as from-space
+ for (bd = gen->old_blocks; bd; bd = bd->link) {
+ bd->flags &= ~BF_EVACUATED;
+ }
+
+ // mark the large objects as from-space
+ for (bd = gen->large_objects; bd; bd = bd->link) {
+ bd->flags &= ~BF_EVACUATED;
+ }
+
+ // for a compacted generation, we need to allocate the bitmap
+ if (gen->mark) {
+ nat bitmap_size; // in bytes
+ bdescr *bitmap_bdescr;
+ StgWord *bitmap;
+
+ bitmap_size = gen->n_old_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
+
+ if (bitmap_size > 0) {
+ bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size)
+ / BLOCK_SIZE);
+ gen->bitmap = bitmap_bdescr;
+ bitmap = bitmap_bdescr->start;
+
+ debugTrace(DEBUG_gc, "bitmap_size: %d, bitmap: %p",
+ bitmap_size, bitmap);
+
+ // don't forget to fill it with zeros!
+ memset(bitmap, 0, bitmap_size);
+
+ // For each block in this step, point to its bitmap from the
+ // block descriptor.
+ for (bd=gen->old_blocks; bd != NULL; bd = bd->link) {
+ bd->u.bitmap = bitmap;
+ bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
+
+ // Also at this point we set the BF_MARKED flag
+ // for this block. The invariant is that
+ // BF_MARKED is always unset, except during GC
+ // when it is set on those blocks which will be
+ // compacted.
+ if (!(bd->flags & BF_FRAGMENTED)) {
+ bd->flags |= BF_MARKED;
+ }
+
+ // BF_SWEPT should be marked only for blocks that are being
+ // collected in sweep()
+ bd->flags &= ~BF_SWEPT;
+ }
+ }
+ }
+}
+
+
+/* ----------------------------------------------------------------------------
+ Save the mutable lists in saved_mut_lists
+ ------------------------------------------------------------------------- */
+
+static void
+stash_mut_list (Capability *cap, nat gen_no)
+{
+ cap->saved_mut_lists[gen_no] = cap->mut_lists[gen_no];
+ cap->mut_lists[gen_no] = allocBlock_sync();
+}
+
+/* ----------------------------------------------------------------------------
+ Initialise a generation that is *not* to be collected
+ ------------------------------------------------------------------------- */
+
+static void
+prepare_uncollected_gen (generation *gen)
+{
+ nat i;
+
+
+ ASSERT(gen->no > 0);
+
+ // save the current mutable lists for this generation, and
+ // allocate a fresh block for each one. We'll traverse these
+ // mutable lists as roots early on in the GC.
+ for (i = 0; i < n_capabilities; i++) {
+ stash_mut_list(&capabilities[i], gen->no);
+ }
+
+ ASSERT(gen->scavenged_large_objects == NULL);
+ ASSERT(gen->n_scavenged_large_blocks == 0);
+}
+
+/* -----------------------------------------------------------------------------
+ Collect the completed blocks from a GC thread and attach them to
+ the generation.
+ -------------------------------------------------------------------------- */
+
+static void
+collect_gct_blocks (void)
+{
+ nat g;
+ gen_workspace *ws;
+ bdescr *bd, *prev;
+
+ for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
+ ws = &gct->gens[g];
+
+ // there may still be a block attached to ws->todo_bd;
+ // leave it there to use next time.
+
+ if (ws->scavd_list != NULL) {
+ ACQUIRE_SPIN_LOCK(&ws->gen->sync);
+
+ ASSERT(gct->scan_bd == NULL);
+ ASSERT(countBlocks(ws->scavd_list) == ws->n_scavd_blocks);
+
+ prev = NULL;
+ for (bd = ws->scavd_list; bd != NULL; bd = bd->link) {
+ ws->gen->n_words += bd->free - bd->start;
+ prev = bd;
+ }
+ if (prev != NULL) {
+ prev->link = ws->gen->blocks;
+ ws->gen->blocks = ws->scavd_list;
+ }
+ ws->gen->n_blocks += ws->n_scavd_blocks;
+
+ ws->scavd_list = NULL;
+ ws->n_scavd_blocks = 0;
+
+ RELEASE_SPIN_LOCK(&ws->gen->sync);
+ }
+ }
+}
+
+/* -----------------------------------------------------------------------------
+ Initialise a gc_thread before GC
+ -------------------------------------------------------------------------- */
+
+static void
+init_gc_thread (gc_thread *t)
+{
+ t->static_objects = END_OF_STATIC_LIST;
+ t->scavenged_static_objects = END_OF_STATIC_LIST;
+ t->scan_bd = NULL;
+ t->mut_lists = t->cap->mut_lists;
+ t->evac_gen_no = 0;
+ t->failed_to_evac = rtsFalse;
+ t->eager_promotion = rtsTrue;
+ t->thunk_selector_depth = 0;
+ t->copied = 0;
+ t->scanned = 0;
+ t->any_work = 0;
+ t->no_work = 0;
+ t->scav_find_work = 0;
+}
+
+/* -----------------------------------------------------------------------------
+ Function we pass to evacuate roots.
+ -------------------------------------------------------------------------- */
+
+static void
+mark_root(void *user USED_IF_THREADS, StgClosure **root)
+{
+ // we stole a register for gct, but this function is called from
+ // *outside* the GC where the register variable is not in effect,
+ // so we need to save and restore it here. NB. only call
+ // mark_root() from the main GC thread, otherwise gct will be
+ // incorrect.
+ gc_thread *saved_gct;
+ saved_gct = gct;
+ SET_GCT(user);
+
+ evacuate(root);
+
+ SET_GCT(saved_gct);