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resolved: make sure we don't get confused when notifying transactions while they are destroyed 

A failing transaction might cause other transactions to fail too, and
thus the set of transactions to notify for a transaction might change
while we are notifying them. Protect against that.
This commit is contained in:
Lennart Poettering 2015-12-18 14:23:48 +01:00
parent a0c888c78c
commit f7014757fd
1 changed files with 31 additions and 3 deletions
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34
src/resolve/resolved-dns-transaction.c
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@ -245,14 +245,42 @@ void dns_transaction_complete(DnsTransaction *t, DnsTransactionState state) {
/* Notify all queries that are interested, but make sure the
* transaction isn't freed while we are still looking at it */
t->block_gc++;
SET_FOREACH(c, t->notify_query_candidates, i)
dns_query_candidate_notify(c);
SET_FOREACH(z, t->notify_zone_items, i)
dns_zone_item_notify(z);
SET_FOREACH(d, t->notify_transactions, i)
dns_transaction_notify(d, t);
t->block_gc--;
if (!set_isempty(t->notify_transactions)) {
DnsTransaction **nt;
unsigned j, n = 0;
/* We need to be careful when notifying other
* transactions, as that might destroy other
* transactions in our list. Hence, in order to be
* able to safely iterate through the list of
* transactions, take a GC lock on all of them
* first. Then, in a second loop, notify them, but
* first unlock that specific transaction. */
nt = newa(DnsTransaction*, set_size(t->notify_transactions));
SET_FOREACH(d, t->notify_transactions, i) {
nt[n++] = d;
d->block_gc++;
}
assert(n == set_size(t->notify_transactions));
for (j = 0; j < n; j++) {
if (set_contains(t->notify_transactions, nt[j]))
dns_transaction_notify(nt[j], t);
nt[j]->block_gc--;
dns_transaction_gc(nt[j]);
}
}
t->block_gc--;
dns_transaction_gc(t);
}