Merge branch 'fanf-urcu-qsbr-build' into 'main'

Fixes for liburcu-qsbr

Closes #4067

See merge request isc-projects/bind9!7925

.tsan-suppress

@@ -1,4 +1,4 @@
 # be more selective with liburcu
 race:rcu_barrier
-race:rcu_memb_barrier
+race:rcu_*_barrier
 thread:*

lib/dns/qp.c

@@ -1169,8 +1169,7 @@ dns_qpmulti_commit(dns_qpmulti_t *multi, dns_qp_t **qptp) {
 	/* paired with chunk_free() */
 	isc_refcount_increment(&qp->base->refcount);
 
-	/* reader_open() below has the matching atomic_load_acquire() */
-	atomic_store_release(&multi->reader, reader); /* COMMIT */
+	rcu_assign_pointer(multi->reader, reader); /* COMMIT */
 
 	/* clean up what we can right now */
 	if (qp->transaction_mode == QP_UPDATE || QP_NEEDGC(qp)) {
@@ -1249,8 +1248,7 @@ dns_qpmulti_rollback(dns_qpmulti_t *multi, dns_qp_t **qptp) {
 static dns_qpmulti_t *
 reader_open(dns_qpmulti_t *multi, dns_qpreadable_t qpr) {
 	dns_qpreader_t *qp = dns_qpreader(qpr);
-	/* dns_qpmulti_commit() has the matching atomic_store_release() */
-	qp_node_t *reader = atomic_load_acquire(&multi->reader);
+	qp_node_t *reader = rcu_dereference(multi->reader);
 	if (reader == NULL) {
 		QP_INIT(qp, multi->writer.methods, multi->writer.uctx);
 	} else {

lib/dns/qp_p.h

@@ -549,8 +549,8 @@ struct dns_qp {
  */
 struct dns_qpmulti {
 	uint32_t magic;
-	/*% pointer to current packed reader */
-	atomic_ptr(qp_node_t) reader;
+	/*% RCU-protected pointer to current packed reader */
+	qp_node_t *reader;
 	/*% the mutex protects the rest of this structure */
 	isc_mutex_t mutex;
 	/*% ref_ptr(writer, reader_ref) == reader */

lib/isc/include/isc/urcu.h

@@ -109,12 +109,12 @@
 #define synchronize_rcu() isc_qsbr_syncronize_rcu()
 
 #define isc_qsbr_rcu_dereference(ptr)              \
-	{                                          \
+	({                                         \
 		if (!urcu_qsbr_read_ongoing()) {   \
 			urcu_qsbr_thread_online(); \
 		}                                  \
-		urcu_qsbr_dereference(ptr);        \
-	}
+		_rcu_dereference(ptr);             \
+	})
 
 #undef rcu_dereference
 #define rcu_dereference(ptr) isc_qsbr_rcu_dereference(ptr)

lib/isc/lib.c

@@ -18,6 +18,7 @@
 #include <isc/mem.h>
 #include <isc/os.h>
 #include <isc/tls.h>
+#include <isc/urcu.h>
 #include <isc/util.h>
 #include <isc/uv.h>
 #include <isc/xml.h>
@@ -51,6 +52,7 @@ isc__initialize(void) {
 	isc__md_initialize();
 	isc__iterated_hash_initialize();
 	(void)isc_os_ncpus();
+	rcu_register_thread();
 }
 
 void
@@ -63,4 +65,6 @@ isc__shutdown(void) {
 	isc__mem_shutdown();
 	isc__mutex_shutdown();
 	isc__os_shutdown();
+	/* should be after isc__mem_shutdown() which calls rcu_barrier() */
+	rcu_unregister_thread();
 }

lib/isc/loop.c

@@ -436,8 +436,6 @@ isc_loopmgr_run(isc_loopmgr_t *loopmgr) {
 
 	bool free_call_rcu_data = !create_all_cpu_call_rcu_data(0);
 
-	rcu_register_thread();
-
 	/*
 	 * The thread 0 is this one.
 	 */
@@ -453,8 +451,6 @@ isc_loopmgr_run(isc_loopmgr_t *loopmgr) {
 
 	isc_thread_main(loop_thread, &loopmgr->loops[0]);
 
-	rcu_unregister_thread();
-
 	rcu_barrier();
 
 	if (free_call_rcu_data) {

tests/libtest/qp.c

@@ -232,7 +232,7 @@ qp_test_dumpqp(dns_qp_t *qp) {
 void
 qp_test_dumpmulti(dns_qpmulti_t *multi) {
 	dns_qpreader_t qpr;
-	qp_node_t *reader = atomic_load(&multi->reader);
+	qp_node_t *reader = rcu_dereference(multi->reader);
 	dns_qpmulti_t *whence = unpack_reader(&qpr, reader);
 	dumpqp(&multi->writer, "qpmulti->writer");
 	printf("qpmulti->reader %p root_ref %u %u:%u base %p\n", reader,