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fix: dev: Try to skip lock on fully lower names

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If the name is fully lowercase, we don't need to access the case bitmap in order to set the case. Therefore, we can check for the FULLYLOWERCASE flag using only atomic operations, and skip a lock in the hot path, provided we clear the FULLYLOWERCASE flag before changing the case bitmap.

Merge branch 'alessio/skip-lock-on-fully-lower-names' into 'main'

See merge request isc-projects/bind9!10497
This commit is contained in:
Ondřej Surý 2025-06-04 10:48:18 +00:00
commit 59585e2294
1 changed files with 8 additions and 10 deletions
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18
lib/dns/rdataslab.c
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@ -870,7 +870,7 @@ dns_slabheader_reset(dns_slabheader_t *h, dns_db_t *db, dns_dbnode_t *node) {
atomic_init(&h->attributes, 0);
atomic_init(&h->last_refresh_fail_ts, 0);
STATIC_ASSERT((sizeof(h->attributes) == 2),
STATIC_ASSERT(sizeof(h->attributes) == 2,
"The .attributes field of dns_slabheader_t needs to be "
"16-bit int type exactly.");
}
@ -1208,6 +1208,8 @@ static void
rdataset_setownercase(dns_rdataset_t *rdataset, const dns_name_t *name) {
dns_slabheader_t *header = dns_rdataset_getheader(rdataset);
DNS_SLABHEADER_CLRATTR(header, DNS_SLABHEADERATTR_CASEFULLYLOWER);
dns_db_locknode(header->db, header->node, isc_rwlocktype_write);
dns_slabheader_setownercase(header, name);
dns_db_unlocknode(header->db, header->node, isc_rwlocktype_write);
@ -1219,15 +1221,13 @@ rdataset_getownercase(const dns_rdataset_t *rdataset, dns_name_t *name) {
uint8_t mask = (1 << 7);
uint8_t bits = 0;
dns_db_locknode(header->db, header->node, isc_rwlocktype_read);
if (!CASESET(header)) {
goto unlock;
}
if (CASEFULLYLOWER(header)) {
isc_ascii_lowercopy(name->ndata, name->ndata, name->length);
} else {
return;
}
dns_db_locknode(header->db, header->node, isc_rwlocktype_read);
if (CASESET(header)) {
uint8_t *nd = name->ndata;
for (size_t i = 0; i < name->length; i++) {
if (mask == (1 << 7)) {
@ -1240,8 +1240,6 @@ rdataset_getownercase(const dns_rdataset_t *rdataset, dns_name_t *name) {
: isc_ascii_tolower(nd[i]);
}
}
unlock:
dns_db_unlocknode(header->db, header->node, isc_rwlocktype_read);
}