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fix interaction of place-channel receive and GC

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Avoid holding onto a pointer into a place-message page beyond
receipt of the message.

Merge to v5.3
This commit is contained in:
Matthew Flatt 2012-07-28 11:06:25 -06:00
parent d8d043d678
commit 8fc008c569
1 changed files with 31 additions and 13 deletions
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44
src/racket/src/place.c
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@ -2589,7 +2589,11 @@ static Scheme_Object *places_serialize(Scheme_Object *so, void **msg_memory, Sch
#endif #endif
} }
Scheme_Object *scheme_places_deserialize(Scheme_Object *so, void *msg_memory) { Scheme_Object *scheme_places_deserialize(Scheme_Object *so, void *msg_memory)
/* The caller must immediately drop any reference to `so' and
`msg_memory' after this function returns; otherwise, since the
`msg_memory' page may be deallocated, a GC could crash. */
{
#if defined(MZ_USE_PLACES) && defined(MZ_PRECISE_GC) #if defined(MZ_USE_PLACES) && defined(MZ_PRECISE_GC)
Scheme_Object *new_so = so; Scheme_Object *new_so = so;
@ -2600,6 +2604,8 @@ Scheme_Object *scheme_places_deserialize(Scheme_Object *so, void *msg_memory) {
if (GC_message_objects_size(msg_memory) < 1024) { if (GC_message_objects_size(msg_memory) < 1024) {
new_so = do_places_deep_copy(so, mzPDC_UNCOPY, 1, NULL, NULL); new_so = do_places_deep_copy(so, mzPDC_UNCOPY, 1, NULL, NULL);
GC_dispose_short_message_allocator(msg_memory); GC_dispose_short_message_allocator(msg_memory);
/* from this point, we must return immediately, so that any
reference to `so' can be dropped before GC. */
msg_memory = NULL; msg_memory = NULL;
} }
else { else {
@ -3096,7 +3102,9 @@ static void register_place_object_with_channel(Scheme_Place_Async_Channel *ch, S
} }
} }
static Scheme_Object *scheme_place_async_try_receive_raw(Scheme_Place_Async_Channel *ch, void **msg_memory_ptr) { static Scheme_Object *scheme_place_async_try_receive_raw(Scheme_Place_Async_Channel *ch, void **msg_memory_ptr)
/* The result must not be retained past extraction from `*msg_memory_ptr'! */
{
Scheme_Object *msg = NULL; Scheme_Object *msg = NULL;
void *msg_memory = NULL; void *msg_memory = NULL;
intptr_t sz; intptr_t sz;
@ -3160,18 +3168,19 @@ static int scheme_place_async_ch_ready(Scheme_Place_Async_Channel *ch) {
mzrt_mutex_unlock(ch->lock); mzrt_mutex_unlock(ch->lock);
return ready; return ready;
} }
static Scheme_Object *place_channel_finish_ready(void *d, int argc, struct Scheme_Object *argv[]) {
static Scheme_Object *place_channel_finish_ready(void *d, int argc, struct Scheme_Object *argv[])
{
Scheme_Object *msg; Scheme_Object *msg;
Scheme_Thread *p = scheme_current_thread;
msg = argv[0]; msg = *(Scheme_Object **)d;
BEGIN_ESCAPEABLE(cleanup_msg_memmory, p);
msg = scheme_places_deserialize(msg, p->place_channel_msg_in_flight);
p->place_channel_msg_in_flight = NULL;
END_ESCAPEABLE();
if (msg) {
Scheme_Thread *p = scheme_current_thread;
BEGIN_ESCAPEABLE(cleanup_msg_memmory, p);
msg = scheme_places_deserialize(msg, p->place_channel_msg_in_flight);
p->place_channel_msg_in_flight = NULL;
END_ESCAPEABLE();
}
return msg; return msg;
} }
@ -3189,10 +3198,19 @@ static int place_channel_ready(Scheme_Object *so, Scheme_Schedule_Info *sinfo) {
msg = scheme_place_async_try_receive_raw((Scheme_Place_Async_Channel *) ch->recvch, &msg_memory); msg = scheme_place_async_try_receive_raw((Scheme_Place_Async_Channel *) ch->recvch, &msg_memory);
if (msg != NULL) { if (msg != NULL) {
Scheme_Object **msg_holder;
Scheme_Thread *p = ((Syncing *)(sinfo->current_syncing))->thread; Scheme_Thread *p = ((Syncing *)(sinfo->current_syncing))->thread;
/* Hold `msg' in atomic memory, because we're not allowed to hold onto
it beyond release of msg_memory, and `wrapper' and the result
flow into the evt system in general. */
msg_holder = (Scheme_Object **)scheme_malloc_atomic(sizeof(Scheme_Object*));
*msg_holder = msg;
p->place_channel_msg_in_flight = msg_memory; p->place_channel_msg_in_flight = msg_memory;
wrapper = scheme_make_closed_prim(place_channel_finish_ready, NULL); wrapper = scheme_make_closed_prim(place_channel_finish_ready, msg_holder);
scheme_set_sync_target(sinfo, msg, wrapper, NULL, 0, 0, NULL); scheme_set_sync_target(sinfo, scheme_void, wrapper, NULL, 0, 0, NULL);
return 1; return 1;
} }
return 0; return 0;