Abstract bucket lock selection logic

Recovering the node lock from a pointer to the header and a pointer to
the db is a common operation. This commit abstracts it away into a
function, so that the node lock selection logic may be modified more
easily.

diff --git a/lib/dns/qpzone.c b/lib/dns/qpzone.c
index 9aed34098313d6a93143c66fad41601e2738e279..c3adb7127a8f63c87a3d62741f181a253fd1a74b 100644 (file)
--- a/lib/dns/qpzone.c
+++ b/lib/dns/qpzone.c
@@ -91,7 +91,9 @@
 #define QPDB_ATTR_LOADED  0x01
 #define QPDB_ATTR_LOADING 0x02
 
+#ifndef DEFAULT_BUCKETS_COUNT
 #define DEFAULT_BUCKETS_COUNT 17 /*%< Should be prime. */
+#endif
 
 #define QPDBITER_NSEC3_ORIGIN_NODE(qpdb, iterator)        \
        ((iterator)->current == &(iterator)->nsec3iter && \
@@ -108,6 +110,15 @@
 typedef struct qpzonedb qpzonedb_t;
 typedef struct qpznode qpznode_t;
 
+typedef struct qpzone_bucket {
+       /* Per-bucket lock. */
+       isc_rwlock_t lock;
+
+       /* Padding to prevent false sharing between locks. */
+       uint8_t __padding[ISC_OS_CACHELINE_SIZE -
+                         (sizeof(isc_rwlock_t)) % ISC_OS_CACHELINE_SIZE];
+} qpzone_bucket_t;
+
 typedef struct qpz_changed {
        qpznode_t *node;
        bool dirty;
@@ -185,15 +196,6 @@ struct qpznode {
        void *data;
 };
 
-typedef struct qpzone_bucket {
-       /* Per-bucket lock. */
-       isc_rwlock_t lock;
-
-       /* Padding to prevent false sharing between locks. */
-       uint8_t __padding[ISC_OS_CACHELINE_SIZE -
-                         (sizeof(isc_rwlock_t)) % ISC_OS_CACHELINE_SIZE];
-} qpzone_bucket_t;
-
 struct qpzonedb {
        /* Unlocked. */
        dns_db_t common;
@@ -239,8 +241,7 @@ struct qpzonedb {
        dns_qpmulti_t *nsec;  /* NSEC nodes only */
        dns_qpmulti_t *nsec3; /* NSEC3 nodes only */
 
-       size_t buckets_count;
-       qpzone_bucket_t buckets[]; /* attribute((counted_by(buckets_count))) */
+       qpzone_bucket_t buckets[DEFAULT_BUCKETS_COUNT];
 };
 
 #ifdef DNS_DB_NODETRACE
@@ -404,6 +405,16 @@ static atomic_uint_fast16_t init_count = 0;
  * Failure to follow this hierarchy can result in deadlock.
  */
 
+static isc_rwlock_t *
+qpzone_get_lock(qpzonedb_t *qpdb, qpznode_t *node) {
+       return &qpdb->buckets[node->locknum].lock;
+}
+
+static uint16_t
+qpzone_get_locknum(void) {
+       return isc_random_uniform(DEFAULT_BUCKETS_COUNT);
+}
+
 /*%
  * Return which RRset should be resigned sooner.  If the RRsets have the
  * same signing time, prefer the other RRset over the SOA RRset.
@@ -507,7 +518,7 @@ free_db_rcu(struct rcu_head *rcu_head) {
        if (dns_name_dynamic(&qpdb->common.origin)) {
                dns_name_free(&qpdb->common.origin, qpdb->common.mctx);
        }
-       for (size_t i = 0; i < qpdb->buckets_count; i++) {
+       for (size_t i = 0; i < DEFAULT_BUCKETS_COUNT; i++) {
                NODE_DESTROYLOCK(&qpdb->buckets[i].lock);
        }
 
@@ -532,9 +543,7 @@ free_db_rcu(struct rcu_head *rcu_head) {
                INSIST(!cds_lfht_destroy(qpdb->common.update_listeners, NULL));
        }
 
-       isc_mem_putanddetach(&qpdb->common.mctx, qpdb,
-                            sizeof(*qpdb) + qpdb->buckets_count *
-                                                    sizeof(qpdb->buckets[0]));
+       isc_mem_putanddetach(&qpdb->common.mctx, qpdb, sizeof(*qpdb));
 }
 
 static void
@@ -595,7 +604,7 @@ new_qpznode(qpzonedb_t *qpdb, const dns_name_t *name) {
        *newdata = (qpznode_t){
                .name = DNS_NAME_INITEMPTY,
                .references = ISC_REFCOUNT_INITIALIZER(1),
-               .locknum = isc_random_uniform(qpdb->buckets_count),
+               .locknum = qpzone_get_locknum(),
        };
 
        isc_mem_attach(qpdb->common.mctx, &newdata->mctx);
@@ -636,14 +645,11 @@ dns__qpzone_create(isc_mem_t *mctx, const dns_name_t *origin, dns_dbtype_t type,
        isc_result_t result;
        dns_qp_t *qp = NULL;
 
-       qpdb = isc_mem_get(mctx,
-                          sizeof(*qpdb) + DEFAULT_BUCKETS_COUNT *
-                                                  sizeof(qpdb->buckets[0]));
+       qpdb = isc_mem_get(mctx, sizeof(*qpdb));
        *qpdb = (qpzonedb_t){
                .common.origin = DNS_NAME_INITEMPTY,
                .common.rdclass = rdclass,
                .common.references = ISC_REFCOUNT_INITIALIZER(1),
-               .buckets_count = DEFAULT_BUCKETS_COUNT,
                .current_serial = 1,
                .least_serial = 1,
                .next_serial = 2,
@@ -662,7 +668,7 @@ dns__qpzone_create(isc_mem_t *mctx, const dns_name_t *origin, dns_dbtype_t type,
 
        isc_heap_create(mctx, resign_sooner, set_index, 0, &qpdb->heap);
 
-       for (size_t i = 0; i < qpdb->buckets_count; i++) {
+       for (size_t i = 0; i < DEFAULT_BUCKETS_COUNT; i++) {
                NODE_INITLOCK(&qpdb->buckets[i].lock);
        }
 
@@ -944,7 +950,7 @@ qpznode_release(qpzonedb_t *qpdb, qpznode_t *node, uint32_t least_serial,
                 * erefs_increment.  If another thread acquires reference it
                 * will be larger than 0, if it doesn't it is going to be 0.
                 */
-               isc_rwlock_t *nlock = &qpdb->buckets[node->locknum].lock;
+               isc_rwlock_t *nlock = qpzone_get_lock(qpdb, node);
                qpznode_erefs_increment(qpdb, node DNS__DB_FLARG_PASS);
                NODE_FORCEUPGRADE(nlock, nlocktypep);
                if (!qpznode_erefs_decrement(qpdb, node DNS__DB_FLARG_PASS)) {
@@ -1038,7 +1044,7 @@ setnsec3parameters(dns_db_t *db, qpz_version_t *version) {
 
        version->havensec3 = false;
        node = qpdb->origin;
-       nlock = &qpdb->buckets[node->locknum].lock;
+       nlock = qpzone_get_lock(qpdb, node);
        NODE_RDLOCK(nlock, &nlocktype);
        for (header = node->data; header != NULL; header = header_next) {
                header_next = header->next;
@@ -1498,7 +1504,7 @@ closeversion(dns_db_t *db, dns_dbversion_t **versionp,
 
                ISC_LIST_UNLINK(resigned_list, header, link);
 
-               nlock = &qpdb->buckets[HEADERNODE(header)->locknum].lock;
+               nlock = qpzone_get_lock(qpdb, HEADERNODE(header));
                NODE_WRLOCK(nlock, &nlocktype);
                if (rollback && !IGNORE(header)) {
                        resigninsert(qpdb, header);
@@ -1518,7 +1524,7 @@ closeversion(dns_db_t *db, dns_dbversion_t **versionp,
                isc_rwlocktype_t nlocktype = isc_rwlocktype_none;
 
                node = changed->node;
-               nlock = &qpdb->buckets[node->locknum].lock;
+               nlock = qpzone_get_lock(qpdb, node);
 
                NODE_WRLOCK(nlock, &nlocktype);
                if (rollback) {
@@ -1562,7 +1568,7 @@ qpzone_findrdataset(dns_db_t *db, dns_dbnode_t *dbnode,
        }
        serial = version->serial;
 
-       nlock = &qpdb->buckets[node->locknum].lock;
+       nlock = qpzone_get_lock(qpdb, node);
        NODE_RDLOCK(nlock, &nlocktype);
 
        matchtype = DNS_TYPEPAIR_VALUE(type, covers);
@@ -2168,7 +2174,7 @@ loading_addrdataset(void *arg, const dns_name_t *name,
                newheader->resign_lsb = rdataset->resign & 0x1;
        }
 
-       nlock = &qpdb->buckets[node->locknum].lock;
+       nlock = qpzone_get_lock(qpdb, node);
        NODE_WRLOCK(nlock, &nlocktype);
        result = add(qpdb, node, name, qpdb->current_version, newheader,
                     DNS_DBADD_MERGE, true, NULL, 0 DNS__DB_FLARG_PASS);
@@ -2377,7 +2383,7 @@ setsigningtime(dns_db_t *db, dns_rdataset_t *rdataset, isc_stdtime_t resign) {
 
        header = dns_rdataset_getheader(rdataset);
 
-       nlock = &qpdb->buckets[HEADERNODE(header)->locknum].lock;
+       nlock = qpzone_get_lock(qpdb, HEADERNODE(header));
        NODE_WRLOCK(nlock, &nlocktype);
 
        oldheader = *header;
@@ -2420,7 +2426,6 @@ getsigningtime(dns_db_t *db, isc_stdtime_t *resign, dns_name_t *foundname,
        dns_slabheader_t *header = NULL;
        isc_rwlocktype_t nlocktype = isc_rwlocktype_none;
        isc_rwlock_t *nlock = NULL;
-       uint16_t locknum;
        isc_result_t result = ISC_R_NOTFOUND;
 
        REQUIRE(VALID_QPZONE(qpdb));
@@ -2434,20 +2439,21 @@ getsigningtime(dns_db_t *db, isc_stdtime_t *resign, dns_name_t *foundname,
                RWUNLOCK(&qpdb->lock, isc_rwlocktype_read);
                return ISC_R_NOTFOUND;
        }
-       locknum = HEADERNODE(header)->locknum;
+       nlock = qpzone_get_lock(qpdb, HEADERNODE(header));
        RWUNLOCK(&qpdb->lock, isc_rwlocktype_read);
 
 again:
-       nlock = &qpdb->buckets[locknum].lock;
-
        NODE_RDLOCK(nlock, &nlocktype);
 
        RWLOCK(&qpdb->lock, isc_rwlocktype_read);
        header = isc_heap_element(qpdb->heap, 1);
-       if (header != NULL && HEADERNODE(header)->locknum != locknum) {
+       if (header != NULL &&
+           qpzone_get_lock(qpdb, HEADERNODE(header)) != nlock)
+       {
                RWUNLOCK(&qpdb->lock, isc_rwlocktype_read);
                NODE_UNLOCK(nlock, &nlocktype);
-               locknum = HEADERNODE(header)->locknum;
+
+               nlock = qpzone_get_lock(qpdb, HEADERNODE(header));
                goto again;
        }
 
@@ -2632,8 +2638,7 @@ qpzone_setup_delegation(qpz_search_t *search, dns_dbnode_t **nodep,
        }
        if (rdataset != NULL) {
                isc_rwlocktype_t nlocktype = isc_rwlocktype_none;
-               isc_rwlock_t *nlock =
-                       &search->qpdb->buckets[node->locknum].lock;
+               isc_rwlock_t *nlock = qpzone_get_lock(search->qpdb, node);
                NODE_RDLOCK(nlock, &nlocktype);
                bindrdataset(search->qpdb, node, search->zonecut_header,
                             rdataset DNS__DB_FLARG_PASS);
@@ -2673,7 +2678,7 @@ step(qpz_search_t *search, dns_qpiter_t *it, direction_t direction,
 
        result = dns_qpiter_current(it, nodename, (void **)&node, NULL);
        while (result == ISC_R_SUCCESS) {
-               isc_rwlock_t *nlock = &qpdb->buckets[node->locknum].lock;
+               isc_rwlock_t *nlock = qpzone_get_lock(qpdb, node);
                isc_rwlocktype_t nlocktype = isc_rwlocktype_none;
                dns_slabheader_t *header_next = NULL;
 
@@ -2838,7 +2843,7 @@ find_wildcard(qpz_search_t *search, qpznode_t **nodep,
 
                dns_qpchain_node(&search->chain, i, NULL, (void **)&node, NULL);
 
-               nlock = &qpdb->buckets[node->locknum].lock;
+               nlock = qpzone_get_lock(qpdb, node);
                NODE_RDLOCK(nlock, &nlocktype);
                /*
                 * First we try to figure out if this node is active in
@@ -2882,7 +2887,7 @@ find_wildcard(qpz_search_t *search, qpznode_t **nodep,
                                 * is active in the search's version, we're
                                 * done.
                                 */
-                               nlock = &qpdb->buckets[wnode->locknum].lock;
+                               nlock = qpzone_get_lock(qpdb, wnode);
                                NODE_RDLOCK(nlock, &nlocktype);
                                for (header = wnode->data; header != NULL;
                                     header = header->next)
@@ -3065,8 +3070,7 @@ again:
        do {
                dns_slabheader_t *found = NULL, *foundsig = NULL;
                isc_rwlocktype_t nlocktype = isc_rwlocktype_none;
-               isc_rwlock_t *nlock =
-                       &search->qpdb->buckets[node->locknum].lock;
+               isc_rwlock_t *nlock = qpzone_get_lock(search->qpdb, node);
                NODE_RDLOCK(nlock, &nlocktype);
                empty_node = true;
                for (header = node->data; header != NULL; header = header_next)
@@ -3209,7 +3213,7 @@ qpzone_check_zonecut(qpznode_t *node, void *arg DNS__DB_FLARG) {
        dns_slabheader_t *found = NULL;
        isc_result_t result = DNS_R_CONTINUE;
        isc_rwlocktype_t nlocktype = isc_rwlocktype_none;
-       isc_rwlock_t *nlock = &search->qpdb->buckets[node->locknum].lock;
+       isc_rwlock_t *nlock = qpzone_get_lock(search->qpdb, node);
 
        NODE_RDLOCK(nlock, &nlocktype);
 
@@ -3498,7 +3502,7 @@ found:
         * have matched a wildcard.
         */
 
-       nlock = &search.qpdb->buckets[node->locknum].lock;
+       nlock = qpzone_get_lock(search.qpdb, node);
        NODE_RDLOCK(nlock, &nlocktype);
 
        if (search.zonecut != NULL) {
@@ -3860,7 +3864,7 @@ tree_exit:
        if (search.need_cleanup) {
                node = search.zonecut;
                INSIST(node != NULL);
-               nlock = &search.qpdb->buckets[node->locknum].lock;
+               nlock = qpzone_get_lock(search.qpdb, node);
 
                NODE_RDLOCK(nlock, &nlocktype);
                qpznode_release(search.qpdb, node, 0,
@@ -3936,7 +3940,7 @@ qpzone_detachnode(dns_db_t *db, dns_dbnode_t **nodep DNS__DB_FLARG) {
 
        node = (qpznode_t *)(*nodep);
        *nodep = NULL;
-       nlock = &qpdb->buckets[node->locknum].lock;
+       nlock = qpzone_get_lock(qpdb, node);
 
        /*
         * qpzone_destroy() uses call_rcu() API to destroy the node locks, so it
@@ -4020,7 +4024,7 @@ locknode(dns_db_t *db, dns_dbnode_t *dbnode, isc_rwlocktype_t type) {
        qpzonedb_t *qpdb = (qpzonedb_t *)db;
        qpznode_t *node = (qpznode_t *)dbnode;
 
-       RWLOCK(&qpdb->buckets[node->locknum].lock, type);
+       RWLOCK(qpzone_get_lock(qpdb, node), type);
 }
 
 static void
@@ -4028,7 +4032,7 @@ unlocknode(dns_db_t *db, dns_dbnode_t *dbnode, isc_rwlocktype_t type) {
        qpzonedb_t *qpdb = (qpzonedb_t *)db;
        qpznode_t *node = (qpznode_t *)dbnode;
 
-       RWUNLOCK(&qpdb->buckets[node->locknum].lock, type);
+       RWUNLOCK(qpzone_get_lock(qpdb, node), type);
 }
 
 static void
@@ -4074,7 +4078,7 @@ rdatasetiter_first(dns_rdatasetiter_t *iterator DNS__DB_FLARG) {
        qpz_version_t *version = (qpz_version_t *)qrditer->common.version;
        dns_slabheader_t *header = NULL, *top_next = NULL;
        isc_rwlocktype_t nlocktype = isc_rwlocktype_none;
-       isc_rwlock_t *nlock = &qpdb->buckets[node->locknum].lock;
+       isc_rwlock_t *nlock = qpzone_get_lock(qpdb, node);
 
        NODE_RDLOCK(nlock, &nlocktype);
 
@@ -4117,7 +4121,7 @@ rdatasetiter_next(dns_rdatasetiter_t *iterator DNS__DB_FLARG) {
        dns_slabheader_t *header = NULL;
        dns_slabheader_t *topheader, *topheader_next = NULL;
        isc_rwlocktype_t nlocktype = isc_rwlocktype_none;
-       isc_rwlock_t *nlock = &qpdb->buckets[node->locknum].lock;
+       isc_rwlock_t *nlock = qpzone_get_lock(qpdb, node);
 
        header = qrditer->current;
        if (header == NULL) {
@@ -4175,7 +4179,7 @@ rdatasetiter_current(dns_rdatasetiter_t *iterator,
        qpznode_t *node = (qpznode_t *)qrditer->common.node;
        dns_slabheader_t *header = NULL;
        isc_rwlocktype_t nlocktype = isc_rwlocktype_none;
-       isc_rwlock_t *nlock = &qpdb->buckets[node->locknum].lock;
+       isc_rwlock_t *nlock = qpzone_get_lock(qpdb, node);
 
        header = qrditer->current;
        REQUIRE(header != NULL);
@@ -4214,7 +4218,7 @@ dereference_iter_node(qpdb_dbiterator_t *iter DNS__DB_FLARG) {
        }
 
        iter->node = NULL;
-       nlock = &qpdb->buckets[node->locknum].lock;
+       nlock = qpzone_get_lock(qpdb, node);
 
        NODE_RDLOCK(nlock, &nlocktype);
        qpznode_release(qpdb, node, 0, &nlocktype DNS__DB_FLARG_PASS);
@@ -4710,7 +4714,7 @@ qpzone_addrdataset(dns_db_t *db, dns_dbnode_t *dbnode,
         * (Note: node lock must be acquired after starting
         * the QPDB transaction and released before committing.)
         */
-       nlock = &qpdb->buckets[node->locknum].lock;
+       nlock = qpzone_get_lock(qpdb, node);
 
        NODE_WRLOCK(nlock, &nlocktype);
 
@@ -4804,7 +4808,7 @@ qpzone_subtractrdataset(dns_db_t *db, dns_dbnode_t *dbnode,
                newheader->resign_lsb = rdataset->resign & 0x1;
        }
 
-       nlock = &qpdb->buckets[node->locknum].lock;
+       nlock = qpzone_get_lock(qpdb, node);
        NODE_WRLOCK(nlock, &nlocktype);
 
        changed = add_changed(newheader, version DNS__DB_FLARG_PASS);
@@ -4966,7 +4970,7 @@ qpzone_deleterdataset(dns_db_t *db, dns_dbnode_t *dbnode,
 
        dns_name_copy(&node->name, nodename);
 
-       nlock = &qpdb->buckets[node->locknum].lock;
+       nlock = qpzone_get_lock(qpdb, node);
        NODE_WRLOCK(nlock, &nlocktype);
        result = add(qpdb, node, nodename, version, newheader, DNS_DBADD_FORCE,
                     false, NULL, 0 DNS__DB_FLARG_PASS);
@@ -4985,7 +4989,7 @@ nodefullname(dns_db_t *db, dns_dbnode_t *node, dns_name_t *name) {
        REQUIRE(node != NULL);
        REQUIRE(name != NULL);
 
-       nlock = &qpdb->buckets[qpnode->locknum].lock;
+       nlock = qpzone_get_lock(qpdb, qpnode);
 
        NODE_RDLOCK(nlock, &nlocktype);
        dns_name_copy(&qpnode->name, name);

diff --git a/tests/dns/qpzone_test.c b/tests/dns/qpzone_test.c
index 7e716bf024d6710ea95c31316964124a43feff36..95c214d53eee4ae51835c057d02a470cfa721e04 100644 (file)
--- a/tests/dns/qpzone_test.c
+++ b/tests/dns/qpzone_test.c
@@ -39,6 +39,7 @@
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wshadow"
 #undef CHECK
+#define DEFAULT_BUCKETS_COUNT 1 /*%< Should be prime. */
 #include "qpzone.c"
 #pragma GCC diagnostic pop
 
@@ -108,7 +109,6 @@ ownercase_test_one(const char *str1, const char *str2) {
        *qpdb = (qpzonedb_t){
                .common.methods = &qpdb_zonemethods,
                .common.mctx = mctx,
-               .buckets_count = 1,
        };
        qpznode_t node = { .locknum = 0 };
        dns_slabheader_t header = {
@@ -176,7 +176,6 @@ ISC_RUN_TEST_IMPL(setownercase) {
        *qpdb = (qpzonedb_t){
                .common.methods = &qpdb_zonemethods,
                .common.mctx = mctx,
-               .buckets_count = 1,
        };
        qpznode_t node = { .locknum = 0 };
        dns_slabheader_t header = {