From: Martin Wilck <mwilck@xxxxxxxx>
Fix this leak in multipathd, reported by valgrind, that messes up
multipathd's otherwise clean leak report:
==23823== 336 bytes in 1 blocks are possibly lost in loss record 3 of 3
==23823== at 0x483AB65: calloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==23823== by 0x4012F16: _dl_allocate_tls (in /lib64/ld-2.31.so)
==23823== by 0x493BB8E: pthread_create@@GLIBC_2.2.5 (in /lib64/libpthread-2.31.so)
==23823== by 0x492A9A9: call_rcu_data_init (urcu-call-rcu-impl.h:437)
==23823== by 0x492AD2F: UnknownInlinedFun (urcu-call-rcu-impl.h:492)
==23823== by 0x492AD2F: create_call_rcu_data_memb (urcu-call-rcu-impl.h:504)
==23823== by 0x1164E3: child.constprop.0.isra.0 (main.c:2915)
==23823== by 0x10F50C: main (main.c:3335)
==23823==
==23823== LEAK SUMMARY:
==23823== definitely lost: 0 bytes in 0 blocks
==23823== indirectly lost: 0 bytes in 0 blocks
==23823== possibly lost: 336 bytes in 1 blocks
The problem is caused by using liburcu's default RCU call handler,
which liburcu refuses to stop/join. See comments in the code.
Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
multipathd/main.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 44 insertions(+), 1 deletion(-)
diff --git a/multipathd/main.c b/multipathd/main.c
index c5c374b..ce14bb6 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -2889,6 +2889,48 @@ set_oom_adj (void)
condlog(0, "couldn't adjust oom score");
}
+/*
+ * Use a non-default call_rcu_data for child().
+ *
+ * We do this to avoid a memory leak from liburcu.
+ * liburcu never frees the default rcu handler (see comments on
+ * call_rcu_data_free() in urcu-call-rcu-impl.h), its thread
+ * can't be joined with pthread_join(), leaving a memory leak.
+ *
+ * Therefore we create our own, which can be destroyed and joined.
+ */
+static struct call_rcu_data *setup_rcu(void)
+{
+ struct call_rcu_data *crdp;
+
+ rcu_init();
+ rcu_register_thread();
+ crdp = create_call_rcu_data(0UL, -1);
+ if (crdp != NULL)
+ set_thread_call_rcu_data(crdp);
+ return crdp;
+}
+
+static struct call_rcu_data *mp_rcu_data;
+
+static void cleanup_rcu(void)
+{
+ pthread_t rcu_thread;
+
+ /* Wait for any pending RCU calls */
+ rcu_barrier();
+ if (mp_rcu_data != NULL) {
+ rcu_thread = get_call_rcu_thread(mp_rcu_data);
+ /* detach this thread from the RCU thread */
+ set_thread_call_rcu_data(NULL);
+ synchronize_rcu();
+ /* tell RCU thread to exit */
+ call_rcu_data_free(mp_rcu_data);
+ pthread_join(rcu_thread, NULL);
+ }
+ rcu_unregister_thread();
+}
+
static int
child (__attribute__((unused)) void *param)
{
@@ -2906,7 +2948,8 @@ child (__attribute__((unused)) void *param)
mlockall(MCL_CURRENT | MCL_FUTURE);
signal_init();
- rcu_init();
+ mp_rcu_data = setup_rcu();
+ atexit(cleanup_rcu);
setup_thread_attr(&misc_attr, 64 * 1024, 0);
setup_thread_attr(&uevent_attr, DEFAULT_UEVENT_STACKSIZE * 1024, 0);
--
2.29.0
--
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