From: Ondřej Surý <ondrej@isc.org>
Date: Thu, 12 Oct 2023 07:17:40 +0000 (+0200)
Subject: Skip the no-op code in adjustsrtt()
X-Git-Tag: v9.19.18~47^2~2
X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=0635bd01cbf47cf05cfa7670fe0833077ccfe6fe;p=thirdparty%2Fbind9.git

Skip the no-op code in adjustsrtt()

If factor == DNS_ADB_RTTADJAGE and addr->entry->lastage == now we would
load value into new_srtt and then immediatelly store it back which
triggers the synchronization between threads using .srtt values.
---

diff --git a/lib/dns/adb.c b/lib/dns/adb.c
index 26f9885ba34..a589519f6ee 100644
--- a/lib/dns/adb.c
+++ b/lib/dns/adb.c
@@ -3057,18 +3057,17 @@ adjustsrtt(dns_adbaddrinfo_t *addr, unsigned int rtt, unsigned int factor,
 			new_srtt -= addr->entry->srtt;
 			new_srtt >>= 9;
 			atomic_store(&addr->entry->lastage, now);
-		} else {
-			new_srtt = atomic_load(&addr->entry->srtt)
+			atomic_store(&addr->entry->srtt, new_srtt);
+			addr->srtt = new_srtt;
 		}
 	} else {
 		new_srtt = ((uint64_t)atomic_load(&addr->entry->srtt) / 10 *
 			    factor) +
 			   ((uint64_t)rtt / 10 * (10 - factor));
+		atomic_store(&addr->entry->srtt, new_srtt);
+		addr->srtt = new_srtt;
 	}
 
-	atomic_store(&addr->entry->srtt, new_srtt);
-	addr->srtt = new_srtt;
-
 	(void)atomic_compare_exchange_strong(&addr->entry->expires,
 					     &(isc_stdtime_t){ 0 },
 					     now + ADB_ENTRY_WINDOW);