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make place-channel receives more fair

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This commit is contained in:
Matthew Flatt 2012-11-25 11:59:17 -07:00
parent 6c0baa0c1e
commit 9062d27d31
2 changed files with 14 additions and 4 deletions
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17
src/racket/src/place.c
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@ -3017,11 +3017,16 @@ static void place_async_send(Scheme_Place_Async_Channel *ch, Scheme_Object *uo)
/*wake up possibly sleeping multiple receiver */ /*wake up possibly sleeping multiple receiver */
else if (SCHEME_VECTORP(ch->wakeup_signal)) { else if (SCHEME_VECTORP(ch->wakeup_signal)) {
Scheme_Object *v = ch->wakeup_signal; Scheme_Object *v = ch->wakeup_signal;
int i; int i, j, delta;
int size = SCHEME_VEC_SIZE(v); int size = SCHEME_VEC_SIZE(v);
int alive = 0; int alive = 0;
for (i = 0; i < size; i++) { /* Try to be fair by cycling through the available places
starting at `delta'. */
delta = ch->delta++;
if (delta < 0) delta = -delta;
for (j = 0; j < size; j++) {
Scheme_Place_Object *o3; Scheme_Place_Object *o3;
i = (j + delta) % size;
o3 = (Scheme_Place_Object *)SCHEME_VEC_ELS(v)[i]; o3 = (Scheme_Place_Object *)SCHEME_VEC_ELS(v)[i];
if (o3) { if (o3) {
int refcount = 0; int refcount = 0;
@ -3119,13 +3124,17 @@ static void register_place_object_with_channel(Scheme_Place_Async_Channel *ch, S
int i = 0; int i = 0;
Scheme_Object *v = ch->wakeup_signal; Scheme_Object *v = ch->wakeup_signal;
int size = SCHEME_VEC_SIZE(v); int size = SCHEME_VEC_SIZE(v);
/* look for unused slot in wakeup vector */ /* already registered? */
for (i = 0; i < size; i++) { for (i = 0; i < size; i++) {
Scheme_Object *vo = SCHEME_VEC_ELS(v)[i]; Scheme_Object *vo = SCHEME_VEC_ELS(v)[i];
if (vo == o) { if (vo == o) {
return; return;
} }
else if (!vo) { }
/* look for unused slot in wakeup vector */
for (i = 0; i < size; i++) {
Scheme_Object *vo = SCHEME_VEC_ELS(v)[i];
if (!vo) {
place_object_inc_refcount(o); place_object_inc_refcount(o);
SCHEME_VEC_ELS(v)[i] = o; SCHEME_VEC_ELS(v)[i] = o;
return; return;

1
src/racket/src/schpriv.h
View File

@ -3906,6 +3906,7 @@ typedef struct Scheme_Place_Async_Channel {
int out; int out;
int count; int count;
int size; int size;
int delta;
#if defined(MZ_USE_PLACES) #if defined(MZ_USE_PLACES)
mzrt_mutex *lock; mzrt_mutex *lock;
#endif #endif