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fix: dev: Call rcu_barrier earlier in the destructor

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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.

Closes #5296

Merge branch '5296-join-rcu-thread-on-shutdown' into 'main'

See merge request isc-projects/bind9!10423
This commit is contained in:
Alessio Podda
2025-04-25 12:30:49 +00:00
parent 336c9d5114 59086c33e2
commit 962b75dca4
2 changed files with 4 additions and 4 deletions
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5
lib/isc/lib.c
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@@ -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();
}

3
lib/isc/mem.c
View File

@@ -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);