static void unpark_waiters_on(Capability *cap, StgTVar *s) {
StgTVarWatchQueue *q;
+ StgTVarWatchQueue *trail;
TRACE("unpark_waiters_on tvar=%p", s);
- for (q = s -> first_watch_queue_entry;
- q != END_STM_WATCH_QUEUE;
+ // unblock TSOs in reverse order, to be a bit fairer (#2319)
+ for (q = s -> first_watch_queue_entry, trail = q;
+ q != END_STM_WATCH_QUEUE;
q = q -> next_queue_entry) {
+ trail = q;
+ }
+ q = trail;
+ for (;
+ q != END_STM_WATCH_QUEUE;
+ q = q -> prev_queue_entry) {
if (watcher_is_tso(q)) {
unpark_tso(cap, (StgTSO *)(q -> closure));
}
StgClosure *stmReadTVar(Capability *cap,
StgTRecHeader *trec,
StgTVar *tvar) {
- StgTRecHeader *entry_in;
+ StgTRecHeader *entry_in = NULL;
StgClosure *result = NULL;
TRecEntry *entry = NULL;
TRACE("%p : stmReadTVar(%p)", trec, tvar);
StgTVar *tvar,
StgClosure *new_value) {
- StgTRecHeader *entry_in;
+ StgTRecHeader *entry_in = NULL;
TRecEntry *entry = NULL;
TRACE("%p : stmWriteTVar(%p, %p)", trec, tvar, new_value);
ASSERT (trec != NO_TREC);