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From: mwilck@suse.com
To: Christophe Varoqui <christophe.varoqui@opensvc.com>,
	Benjamin Marzinski <bmarzins@redhat.com>
Cc: lixiaokeng@huawei.com, dm-devel@redhat.com,
	Martin Wilck <mwilck@suse.com>
Subject: [dm-devel] [PATCH v2 02/29] multipathd: Fix liburcu memory leak
Date: Fri, 16 Oct 2020 12:44:34 +0200
Message-ID: <20201016104501.8700-3-mwilck@suse.com> (raw)
In-Reply-To: <20201016104501.8700-1-mwilck@suse.com>

From: Martin Wilck <mwilck@suse.com>

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.

Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Martin Wilck <mwilck@suse.com>
---
 multipathd/main.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/multipathd/main.c b/multipathd/main.c
index c5c374b..be1b5ae 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -2889,6 +2889,47 @@ 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 void cleanup_rcu(int dummy __attribute__((unused)), void *arg)
+{
+	struct call_rcu_data *crdp = arg;
+	pthread_t rcu_thread;
+
+	/* Wait for any pending RCU calls */
+	rcu_barrier();
+	if (crdp != NULL) {
+		rcu_thread = get_call_rcu_thread(crdp);
+		/* detach this thread from the RCU thread */
+		set_thread_call_rcu_data(NULL);
+		synchronize_rcu();
+		/* tell RCU thread to exit */
+		call_rcu_data_free(crdp);
+		pthread_join(rcu_thread, NULL);
+	}
+	rcu_unregister_thread();
+}
+
 static int
 child (__attribute__((unused)) void *param)
 {
@@ -2903,10 +2944,12 @@ child (__attribute__((unused)) void *param)
 	char *envp;
 	int queue_without_daemon;
 	enum daemon_status state;
+	struct call_rcu_data *crdp;
 
 	mlockall(MCL_CURRENT | MCL_FUTURE);
 	signal_init();
-	rcu_init();
+	crdp = setup_rcu();
+	on_exit(cleanup_rcu, crdp);
 
 	setup_thread_attr(&misc_attr, 64 * 1024, 0);
 	setup_thread_attr(&uevent_attr, DEFAULT_UEVENT_STACKSIZE * 1024, 0);
-- 
2.28.0


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  parent reply index

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-16 10:44 [dm-devel] [PATCH v2 00/29] libmultipath: improve cleanup on exit mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 01/29] multipathd: uxlsnr: avoid deadlock " mwilck
2020-10-20 19:04   ` Benjamin Marzinski
2020-10-16 10:44 ` mwilck [this message]
2020-10-16 10:44 ` [dm-devel] [PATCH v2 03/29] multipathd: move handling of io_err_stat_attr into libmultipath mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 04/29] multipathd: move vecs desctruction into cleanup function mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 05/29] multipathd: make some globals static mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 06/29] multipathd: move threads destruction into separate function mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 07/29] multipathd: move conf " mwilck
2020-10-19 18:56   ` Benjamin Marzinski
2020-10-16 10:44 ` [dm-devel] [PATCH v2 08/29] multipathd: move pid " mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 09/29] multipathd: close pidfile on exit mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 10/29] multipathd: add helper for systemd notification at exit mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 11/29] multipathd: child(): call cleanups in failure case, too mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 12/29] multipathd: unwatch_all_dmevents: check if waiter is initialized mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 13/29] multipathd: print error message if config can't be loaded mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 14/29] libmultipath: add libmp_dm_exit() mwilck
2020-10-19 19:07   ` Benjamin Marzinski
2020-10-16 10:44 ` [dm-devel] [PATCH v2 15/29] multipathd: fixup libdm deinitialization mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 16/29] libmultipath: log_thread_stop(): check if logarea is initialized mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 17/29] multipathd: add cleanup_child() exit handler mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 18/29] libmultipath: fix log_thread startup and teardown mwilck
2020-10-19 20:00   ` Benjamin Marzinski
2020-10-26 13:58     ` Martin Wilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 19/29] multipathd: move cleanup_{prio, checkers, foreign} to libmultipath_exit mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 20/29] multipath: use atexit() for cleanup handlers mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 21/29] mpathpersist: " mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 22/29] multipath: fix leaks in check_path_valid() mwilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 23/29] multipath-tools: mpath-tools.supp: file with valgrind suppressions mwilck
2020-10-19 20:01   ` Benjamin Marzinski
2020-10-16 10:44 ` [dm-devel] [PATCH v2 24/29] libmultipath: use libmp_verbosity to track verbosity mwilck
2020-10-19 20:38   ` Benjamin Marzinski
2020-10-26 14:47     ` Martin Wilck
2020-10-16 10:44 ` [dm-devel] [PATCH v2 25/29] libmultipath: introduce symbolic values for logsink mwilck
2020-10-16 20:13   ` Benjamin Marzinski
2020-10-16 10:44 ` [dm-devel] [PATCH v2 26/29] libmultipath: simplify dlog() mwilck
2020-10-19 21:07   ` Benjamin Marzinski
2020-10-16 10:44 ` [dm-devel] [PATCH v2 27/29] multipathd: common code for "-k" and command args mwilck
2020-10-19 21:51   ` Benjamin Marzinski
2020-10-16 10:45 ` [dm-devel] [PATCH v2 28/29] multipathd: sanitize uxsock_listen() mwilck
2020-10-19 23:33   ` Benjamin Marzinski
2020-10-26 13:54     ` Martin Wilck
2020-10-16 10:45 ` [dm-devel] [PATCH v2 29/29] libmultipath: fix race between log_safe and log_thread_stop() mwilck
2020-10-20  2:20   ` Benjamin Marzinski
2020-10-26 16:22     ` Martin Wilck
2020-10-26 17:24       ` Martin Wilck
2020-11-03  0:11         ` Benjamin Marzinski
2020-11-04 12:36           ` Martin Wilck
2020-11-04 15:46             ` Benjamin Marzinski

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