From: Tony Finch <fanf@isc.org>
Date: Wed, 17 May 2023 09:57:16 +0000 (+0100)
Subject: Acquire qpmulti->mutex during destruction
X-Git-Tag: v9.19.14~36^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b754c6628fc0a69441afbd449890e6b9af0d092a;p=thirdparty%2Fbind9.git

Acquire qpmulti->mutex during destruction

Thread sanitizer warns that parts of the qp-trie are accessed
both with and without the mutex; the unlocked accesses happen during
destruction, so they should be benign, but there's no harm locking
anyway to convince tsan it is clean.

Also, ensure .tsan-suppress and .tsan-suppress-extra are in sync.
---

diff --git a/.tsan-suppress-extra b/.tsan-suppress-extra
index 0f598bf36b3..2e31db7e263 100644
--- a/.tsan-suppress-extra
+++ b/.tsan-suppress-extra
@@ -3,5 +3,5 @@ called_from_lib:libfstrm.so
 called_from_lib:libdummyrpz.so
 # be more selective with liburcu
 race:rcu_barrier
-race:rcu_memb_barrier
+race:rcu_*_barrier
 thread:*
diff --git a/lib/dns/qp.c b/lib/dns/qp.c
index 10d19e1b1b2..afa513f5599 100644
--- a/lib/dns/qp.c
+++ b/lib/dns/qp.c
@@ -1431,14 +1431,22 @@ static void
 qpmulti_destroy_cb(struct rcu_head *arg) {
 	qp_rcuctx_t *rcuctx = isc_urcu_container(arg, qp_rcuctx_t, rcu_head);
 	REQUIRE(QPRCU_VALID(rcuctx));
+	/* only nonzero for reclaim_chunks_cb() */
+	REQUIRE(rcuctx->count == 0);
+
 	dns_qpmulti_t *multi = rcuctx->multi;
 	REQUIRE(QPMULTI_VALID(multi));
+
+	/* reassure thread sanitizer */
+	LOCK(&multi->mutex);
+
 	dns_qp_t *qp = &multi->writer;
 	REQUIRE(QP_VALID(qp));
 
-	REQUIRE(rcuctx->count == 0);
-
 	destroy_guts(qp);
+
+	UNLOCK(&multi->mutex);
+
 	isc_mutex_destroy(&multi->mutex);
 	isc_mem_putanddetach(&rcuctx->mctx, rcuctx,
 			     STRUCT_FLEX_SIZE(rcuctx, chunk, rcuctx->count));