From 59086c33e2edb9ebc4f5b5bc6cde35f851a6f45b Mon Sep 17 00:00:00 2001 From: Your Name Date: Fri, 25 Apr 2025 10:41:29 +0200 Subject: [PATCH] Call rcu_barrier earlier in the destructor If a call_rcu thread is running, there is a possible race condition where the destructors run before all call_rcu callbacks have finished running. This can happen, for example, if the call_rcu callback tries to log something after the logging context has been torn down. In !10394, we tried to counter this by explicitely creating a call_rcu thread an shutting it down before running the destructors, but it is possible for things to "slip" and end up on the default call_rcu thread. As a quickfix, this commit moves an rcu_barrier() that was in the mem context destructor earlier, so that it "protects" all libisc destructors. --- lib/isc/lib.c | 5 +++-- lib/isc/mem.c | 3 +-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/lib/isc/lib.c b/lib/isc/lib.c index bdff8efd35..c0f9d30dba 100644 --- a/lib/isc/lib.c +++ b/lib/isc/lib.c @@ -67,6 +67,9 @@ isc__lib_shutdown(void) { return; } + rcu_barrier(); + rcu_unregister_thread(); + isc__iterated_hash_shutdown(); isc__xml_shutdown(); isc__uv_shutdown(); @@ -75,6 +78,4 @@ isc__lib_shutdown(void) { isc__mem_shutdown(); isc__mutex_shutdown(); isc__os_shutdown(); - /* should be after isc__mem_shutdown() which calls rcu_barrier() */ - rcu_unregister_thread(); } diff --git a/lib/isc/mem.c b/lib/isc/mem.c index c1b0ab7331..ff34485ae0 100644 --- a/lib/isc/mem.c +++ b/lib/isc/mem.c @@ -434,10 +434,9 @@ isc__mem_initialize(void) { void isc__mem_shutdown(void) { + /* should be called after an rcu_barrier() */ bool empty; - rcu_barrier(); - isc__mem_checkdestroyed(); LOCK(&contextslock);