99 lines
3.1 KiB
Diff
99 lines
3.1 KiB
Diff
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Martin Wilck <mwilck@suse.com>
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Date: Wed, 23 Sep 2020 18:02:39 +0200
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Subject: [PATCH] multipathd: Fix liburcu memory leak
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Fix this leak in multipathd, reported by valgrind, that messes up
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multipathd's otherwise clean leak report:
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==23823== 336 bytes in 1 blocks are possibly lost in loss record 3 of 3
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==23823== at 0x483AB65: calloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
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==23823== by 0x4012F16: _dl_allocate_tls (in /lib64/ld-2.31.so)
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==23823== by 0x493BB8E: pthread_create@@GLIBC_2.2.5 (in /lib64/libpthread-2.31.so)
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==23823== by 0x492A9A9: call_rcu_data_init (urcu-call-rcu-impl.h:437)
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==23823== by 0x492AD2F: UnknownInlinedFun (urcu-call-rcu-impl.h:492)
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==23823== by 0x492AD2F: create_call_rcu_data_memb (urcu-call-rcu-impl.h:504)
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==23823== by 0x1164E3: child.constprop.0.isra.0 (main.c:2915)
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==23823== by 0x10F50C: main (main.c:3335)
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==23823==
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==23823== LEAK SUMMARY:
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==23823== definitely lost: 0 bytes in 0 blocks
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==23823== indirectly lost: 0 bytes in 0 blocks
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==23823== possibly lost: 336 bytes in 1 blocks
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The problem is caused by using liburcu's default RCU call handler,
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which liburcu refuses to stop/join. See comments in the code.
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Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
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Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
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---
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multipathd/main.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
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1 file changed, 44 insertions(+), 1 deletion(-)
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diff --git a/multipathd/main.c b/multipathd/main.c
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index c5c374b7..ce14bb66 100644
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--- a/multipathd/main.c
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+++ b/multipathd/main.c
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@@ -2889,6 +2889,48 @@ set_oom_adj (void)
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condlog(0, "couldn't adjust oom score");
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}
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+/*
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+ * Use a non-default call_rcu_data for child().
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+ *
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+ * We do this to avoid a memory leak from liburcu.
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+ * liburcu never frees the default rcu handler (see comments on
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+ * call_rcu_data_free() in urcu-call-rcu-impl.h), its thread
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+ * can't be joined with pthread_join(), leaving a memory leak.
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+ *
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+ * Therefore we create our own, which can be destroyed and joined.
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+ */
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+static struct call_rcu_data *setup_rcu(void)
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+{
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+ struct call_rcu_data *crdp;
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+
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+ rcu_init();
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+ rcu_register_thread();
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+ crdp = create_call_rcu_data(0UL, -1);
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+ if (crdp != NULL)
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+ set_thread_call_rcu_data(crdp);
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+ return crdp;
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+}
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+
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+static struct call_rcu_data *mp_rcu_data;
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+
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+static void cleanup_rcu(void)
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+{
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+ pthread_t rcu_thread;
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+
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+ /* Wait for any pending RCU calls */
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+ rcu_barrier();
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+ if (mp_rcu_data != NULL) {
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+ rcu_thread = get_call_rcu_thread(mp_rcu_data);
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+ /* detach this thread from the RCU thread */
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+ set_thread_call_rcu_data(NULL);
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+ synchronize_rcu();
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+ /* tell RCU thread to exit */
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+ call_rcu_data_free(mp_rcu_data);
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+ pthread_join(rcu_thread, NULL);
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+ }
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+ rcu_unregister_thread();
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+}
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+
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static int
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child (__attribute__((unused)) void *param)
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{
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@@ -2906,7 +2948,8 @@ child (__attribute__((unused)) void *param)
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mlockall(MCL_CURRENT | MCL_FUTURE);
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signal_init();
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- rcu_init();
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+ mp_rcu_data = setup_rcu();
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+ atexit(cleanup_rcu);
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setup_thread_attr(&misc_attr, 64 * 1024, 0);
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setup_thread_attr(&uevent_attr, DEFAULT_UEVENT_STACKSIZE * 1024, 0);
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--
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2.17.2
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