fix a synchronization problem in the GC for places
When a GC is needed for the shared space, a GC is triggered in all places, and the places wait until each other place has completed. However, the places also need to wait until all other places are ready to *start* a GC; otherwise, a place may be modifying a shared record while some other place traverses it for a GC. Closes PR 14229 Merge to v6.0
This commit is contained in:
Matthew Flatt
parent
019c8214ef
commit
280bb31d70
40
pkgs/racket-pkgs/racket-test/tests/racket/place-sync-gc.rkt
Normal file
40
pkgs/racket-pkgs/racket-test/tests/racket/place-sync-gc.rkt
Normal file
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@ -0,0 +1,40 @@
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#lang racket/base
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(require racket/place)
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;; This test (by Eric Dobson) effectively checks synchronization
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;; of GC among places. The `holder` place waits until the main
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;; place triggers a shared-space GC due to a growing message channel.
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;; Since the `holder` place can reach the channel, the GC can go
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;; bad if the `holder` place traverses the channel while the other
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;; place is still installing new message-array (so that the channel
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;; is marked already by the GC, but its content changes).
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(define (holder)
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(place chan
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(let loop ([v #f])
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(define v2 (sync chan))
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(place-channel-put chan v)
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(loop v2))))
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(module+ main
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(define other (holder))
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(define exec (make-will-executor))
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(define exec-thread
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(thread
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(lambda ()
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(let loop ()
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(will-execute exec)
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(loop)))))
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(define in
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(let-values ([(in out) (place-channel)])
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(place-channel-put other out)
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in))
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(collect-garbage)
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;; Let will execute
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(sleep 1)
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(/ (current-memory-use) 1000000.0)
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(for ((i 1000000))
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(place-channel-put in i)))
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(module+ test
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(require (submod ".." main)))
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@ -164,7 +164,8 @@ intptr_t GC_is_place() {
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return postmaster_and_place_gc(gc);
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}
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static void master_collect_initiate(NewGC *gc);
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static void master_collect_request();
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struct Log_Master_Info {
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int ran, full;
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intptr_t pre_used, post_used, pre_admin, post_admin;
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@ -894,10 +895,15 @@ void GC_check_master_gc_request() {
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if (mgc) {
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/* check for GC needed due to GC_report_unsent_message_delta(): */
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if ((mgc->gen0.current_size + mgc->pending_msg_size) >= mgc->gen0.max_size) {
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NewGC *saved_gc;
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saved_gc = GC_switch_to_master_gc();
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master_collect_initiate(mgc);
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GC_switch_back_from_master(saved_gc);
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NewGC *gc = GC_get_GC();
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if (!postmaster_and_master_gc(gc))
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mzrt_rwlock_wrlock(MASTERGCINFO->cangc);
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master_collect_request();
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if (!postmaster_and_master_gc(gc))
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mzrt_rwlock_unlock(MASTERGCINFO->cangc);
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}
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if (mgc->major_places_gc == 1) {
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@ -908,19 +914,47 @@ void GC_check_master_gc_request() {
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}
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#ifdef MZ_USE_PLACES
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static int check_master_wants_to_collect() {
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return (MASTERGC && MASTERGC->major_places_gc);
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static int master_wants_to_collect() {
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if (MASTERGC) {
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int v;
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mzrt_rwlock_rdlock(MASTERGCINFO->cangc);
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v = MASTERGC->major_places_gc;
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mzrt_rwlock_unlock(MASTERGCINFO->cangc);
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return v;
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} else
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return 0;
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}
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#endif
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#ifdef MZ_USE_PLACES
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static void wait_until_master_in_progress(NewGC *gc);
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#endif
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static void collect_now(NewGC *gc, int major)
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{
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#ifdef MZ_USE_PLACES
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if (postmaster_and_master_gc(gc))
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master_collect_initiate(gc);
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else
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master_collect_request();
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else {
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int again;
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do {
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if (!gc->dont_master_gc_until_child_registers && master_wants_to_collect()) {
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wait_until_master_in_progress(gc);
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gc->major_places_gc = 1;
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garbage_collect(gc, 1, 0, NULL); /* waits until all are done */
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gc->major_places_gc = 0;
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} else {
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garbage_collect(gc, major, 0, NULL);
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}
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if (gc->dont_master_gc_until_child_registers)
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again = 0;
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else
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again = master_wants_to_collect();
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} while (again);
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}
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#else
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garbage_collect(gc, major, 0, NULL);
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#endif
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garbage_collect(gc, major, 0, NULL);
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}
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@ -2587,7 +2621,8 @@ static void NewGCMasterInfo_initialize() {
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MASTERGCINFO->signal_fds[i] = (void *)REAPED_SLOT_AVAILABLE;
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}
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mzrt_rwlock_create(&MASTERGCINFO->cangc);
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mzrt_sema_create(&MASTERGCINFO->wait_sema, 0);
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mzrt_sema_create(&MASTERGCINFO->wait_go_sema, 0);
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mzrt_sema_create(&MASTERGCINFO->wait_done_sema, 0);
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}
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#if 0
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@ -2602,10 +2637,10 @@ static void NewGCMasterInfo_cleanup() {
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/* signals every place to do a full gc at then end of
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garbage_collect the places will call
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wait_if_master_in_progress and
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wait_while_master_in_progress and
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rendezvous for a master gc */
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/* this is only called from the master so the cangc lock should already be held */
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static void master_collect_initiate(NewGC *gc) {
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static void master_collect_request() {
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if (MASTERGC->major_places_gc == 0) {
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int i = 0;
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int size = MASTERGCINFO->size;
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@ -2613,7 +2648,7 @@ static void master_collect_initiate(NewGC *gc) {
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MASTERGC->major_places_gc = 1;
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MASTERGCINFO->ready = 0;
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for (i=1; i < size; i++) {
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for (i = 1; i < size; i++) {
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void *signal_fd = MASTERGCINFO->signal_fds[i];
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if (signal_fd < (void*) -2) {
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scheme_signal_received_at(signal_fd);
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@ -2628,11 +2663,11 @@ static void master_collect_initiate(NewGC *gc) {
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MASTERGCINFO->signal_fds[i] = (void*) SIGNALED_BUT_NOT_REGISTERED;
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count++;
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}
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if (count == (MASTERGCINFO->alive -1)) {
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if (count == (MASTERGCINFO->alive - 1)) {
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break;
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}
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}
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if (count != (MASTERGCINFO->alive -1)) {
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if (count != (MASTERGCINFO->alive - 1)) {
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printf("GC2 count != MASTERGCINFO->alive %i %" PRIdPTR "\n", count, MASTERGCINFO->alive);
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abort();
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}
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@ -2663,63 +2698,83 @@ static void collect_master(Log_Master_Info *lmi) {
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int i = 0;
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int alive = MASTERGCINFO->alive;
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/* wake everyone back up, except MASTERGC and ourself */
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for (i=2; i < alive; i++) {
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mzrt_sema_post(MASTERGCINFO->wait_sema);
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for (i = 2; i < alive; i++) {
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mzrt_sema_post(MASTERGCINFO->wait_done_sema);
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}
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}
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}
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GC_switch_back_from_master(saved_gc);
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}
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static void wait_if_master_in_progress(NewGC *gc, Log_Master_Info *lmi) {
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static void sync_master_progress(NewGC *gc, int done, Log_Master_Info *lmi) {
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int last_one_here = -1;
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mzrt_rwlock_wrlock(MASTERGCINFO->cangc);
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GC_LOCK_DEBUG("MGCLOCK wait_if_master_in_progress\n");
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{
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if (MASTERGC->major_places_gc == 1) {
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MASTERGCINFO->ready++;
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if (MASTERGC->major_places_gc == 1) {
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MASTERGCINFO->ready++;
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#if defined(GC_DEBUG_PAGES)
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printf("%i READY\n", gc->place_id);
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GCVERBOSEprintf(gc, "%i READY\n", gc->place_id);
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GCVERBOSEprintf(gc, "START MASTER COLLECTION\n");
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printf("%i READY\n", gc->place_id);
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GCVERBOSEprintf(gc, "%i READY\n", gc->place_id);
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GCVERBOSEprintf(gc, "START MASTER COLLECTION\n");
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#endif
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/* don't count MASTERGC*/
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if ((MASTERGCINFO->alive -1) == MASTERGCINFO->ready) {
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last_one_here = 1;
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}
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else {
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last_one_here = 0;
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}
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}
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else {
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last_one_here = -1;
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/* don't count MASTERGC */
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if ((MASTERGCINFO->alive - 1) == MASTERGCINFO->ready) {
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last_one_here = 1;
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MASTERGCINFO->ready = 0;
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} else {
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last_one_here = 0;
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}
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} else {
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last_one_here = -1;
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}
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GC_LOCK_DEBUG("UNMGCLOCK wait_if_master_in_progress\n");
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mzrt_rwlock_unlock(MASTERGCINFO->cangc);
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switch(last_one_here) {
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case -1:
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/* master doesn't want to collect */
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case -1:
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/* master doesn't want to collect */
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return;
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break;
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case 0:
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/* wait on semaphore */
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mzrt_sema_wait(MASTERGCINFO->wait_sema);
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case 0:
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/* wait on semaphore */
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if (done) {
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mzrt_sema_wait(MASTERGCINFO->wait_done_sema);
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GCVERBOSEprintf(gc, "END MASTER COLLECTION\n");
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} else
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mzrt_sema_wait(MASTERGCINFO->wait_go_sema);
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break;
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case 1:
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/* You're the last one here. */
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collect_master(lmi);
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case 1:
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/* You're the last one here. */
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if (done) {
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collect_master(lmi); /* notifies other places on completion */
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GCVERBOSEprintf(gc, "END MASTER COLLECTION\n");
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} else {
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int i = 0;
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int alive = MASTERGCINFO->alive;
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/* wake everyone back up, except MASTERGC and ourself */
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for (i = 2; i < alive; i++) {
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mzrt_sema_post(MASTERGCINFO->wait_go_sema);
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}
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}
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break;
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default:
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printf("GC2 wait_if_master_in_progress invalid case, unreachable\n");
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abort();
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default:
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printf("GC2 sync_master_in_progress invalid case, unreachable\n");
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abort();
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break;
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}
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}
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static void wait_until_master_in_progress(NewGC *gc) {
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sync_master_progress(gc, 0, NULL);
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}
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static void wait_while_master_in_progress(NewGC *gc, Log_Master_Info *lmi) {
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sync_master_progress(gc, 1, lmi);
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}
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/* MUST CALL WITH cangc lock */
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static intptr_t NewGCMasterInfo_find_free_id() {
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GC_ASSERT(MASTERGCINFO->alive <= MASTERGCINFO->size);
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@ -2912,7 +2967,7 @@ void GC_destruct_child_gc() {
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mzrt_rwlock_unlock(MASTERGCINFO->cangc);
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if (waiting) {
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garbage_collect(gc, 1, 0, NULL);
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collect_now(gc, 1);
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waiting = 1;
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}
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} while (waiting == 1);
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@ -3124,7 +3179,7 @@ void GC_mark2(const void *const_p, struct NewGC *gc)
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if(!(page = pagemap_find_page_for_marking(gc, p, 0))) {
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#ifdef MZ_USE_PLACES
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if (MASTERGC && MASTERGC->major_places_gc && (page = pagemap_find_page(MASTERGC->page_maps, p))) {
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if (gc->major_places_gc && (page = pagemap_find_page(MASTERGC->page_maps, p))) {
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is_a_master_page = 1;
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} else
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#endif
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@ -3343,7 +3398,7 @@ static inline void propagate_marks_worker(NewGC *gc, Mark2_Proc *mark_table, voi
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p = REMOVE_BIG_PAGE_PTR_TAG(pp);
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page = pagemap_find_page_for_marking(gc, p, 0);
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#ifdef MZ_USE_PLACES
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if (!page && MASTERGC && MASTERGC->major_places_gc) {
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if (!page && gc->major_places_gc) {
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page = pagemap_find_page(MASTERGC->page_maps, p);
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}
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#endif
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@ -4617,9 +4672,6 @@ static void garbage_collect(NewGC *gc, int force_full, int switching_master, Log
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uintptr_t old_mem_allocated;
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int next_gc_full;
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#ifdef MZ_USE_PLACES
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int master_wants_to_collect = check_master_wants_to_collect();
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#endif
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old_mem_use = gc->memory_in_use;
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old_gen0 = gc->gen0.current_size;
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@ -4908,10 +4960,10 @@ static void garbage_collect(NewGC *gc, int force_full, int switching_master, Log
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#ifdef MZ_USE_PLACES
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if (postmaster_and_place_gc(gc)) {
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if (gc->gc_full && master_wants_to_collect && !(gc->dont_master_gc_until_child_registers)) {
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if (gc->gc_full && gc->major_places_gc && !(gc->dont_master_gc_until_child_registers)) {
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Log_Master_Info sub_lmi;
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sub_lmi.ran = 0;
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wait_if_master_in_progress(gc, &sub_lmi);
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wait_while_master_in_progress(gc, &sub_lmi);
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if (sub_lmi.ran) {
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if (gc->GC_collect_inform_callback) {
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park_for_inform_callback(gc);
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@ -120,7 +120,8 @@ typedef struct NewGCMasterInfo {
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uintptr_t ready;
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void **signal_fds;
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mzrt_rwlock *cangc;
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mzrt_sema *wait_sema;
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mzrt_sema *wait_go_sema;
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mzrt_sema *wait_done_sema;
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} NewGCMasterInfo;
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#endif
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