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make resolver->zspill atomic to prevent potential deadlock

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(cherry picked from commit 62abb6aa82)
This commit is contained in:
Mark Andrews
2019-12-12 20:22:22 +11:00
parent 623e23e296
commit 02874aa472
1 changed files with 10 additions and 13 deletions
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lib/dns/resolver.c
+10 -13
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@@ -512,16 +512,19 @@ struct dns_resolver {
unsigned int spillatmax;
unsigned int spillatmin;
isc_timer_t * spillattimer;
bool zero_no_soa_ttl;
bool zero_no_soa_ttl;
unsigned int query_timeout;
unsigned int maxdepth;
unsigned int maxqueries;
isc_result_t quotaresp[2];
/* Additions for serve-stale feature. */
unsigned int retryinterval; /* in milliseconds */
unsigned int retryinterval; /* in milliseconds */
unsigned int nonbackofftries;
/* Atomic */
atomic_uint_fast32_t zspill; /* fetches-per-zone */
/* Locked by lock. */
unsigned int references;
bool exiting;
@@ -529,9 +532,8 @@ struct dns_resolver {
unsigned int activebuckets;
bool priming;
unsigned int spillat; /* clients-per-query */
unsigned int zspill; /* fetches-per-zone */
dns_badcache_t * badcache; /* Bad cache. */
dns_badcache_t * badcache; /* Bad cache. */
/* Locked by primelock. */
dns_fetch_t * primefetch;
@@ -1511,7 +1513,7 @@ fcount_incr(fetchctx_t *fctx, bool force) {
isc_result_t result = ISC_R_SUCCESS;
zonebucket_t *dbucket;
fctxcount_t *counter;
unsigned int bucketnum, spill;
unsigned int bucketnum;
REQUIRE(fctx != NULL);
REQUIRE(fctx->res != NULL);
@@ -1520,10 +1522,6 @@ fcount_incr(fetchctx_t *fctx, bool force) {
bucketnum = dns_name_fullhash(&fctx->domain, false)
% RES_DOMAIN_BUCKETS;
LOCK(&fctx->res->lock);
spill = fctx->res->zspill;
UNLOCK(&fctx->res->lock);
dbucket = &fctx->res->dbuckets[bucketnum];
LOCK(&dbucket->lock);
@@ -1550,6 +1548,7 @@ fcount_incr(fetchctx_t *fctx, bool force) {
ISC_LIST_APPEND(dbucket->list, counter, link);
}
} else {
uint_fast32_t spill = atomic_load_acquire(&fctx->res->zspill);
if (!force && spill != 0 && counter->count >= spill) {
counter->dropped++;
fcount_logspill(fctx, counter);
@@ -10074,7 +10073,7 @@ dns_resolver_create(dns_view_t *view,
res->spillatmin = res->spillat = 10;
res->spillatmax = 100;
res->spillattimer = NULL;
res->zspill = 0;
atomic_init(&res->zspill, 0);
res->zero_no_soa_ttl = false;
res->retryinterval = 30000;
res->nonbackofftries = 3;
@@ -11410,9 +11409,7 @@ dns_resolver_setfetchesperzone(dns_resolver_t *resolver, uint32_t clients)
{
REQUIRE(VALID_RESOLVER(resolver));
LOCK(&resolver->lock);
resolver->zspill = clients;
UNLOCK(&resolver->lock);
atomic_store_release(&resolver->zspill, clients);
}