memory leak of global locks (libevent-2.0.21-stable)

[qidu]

test code

void onTimeOut(evutil_socket_t fd, short event, void *arg)
{
        struct event_base* base = (struct event_base*)arg;
        event_base_loopbreak(base);
}
int main(int argc, char* argv[])
{
        int rc = evthread_use_pthreads();
        evthread_enable_lock_debuging();
        struct event_base* base = event_base_new();
        struct event* timeEvent = event_new(base, -1, EV_PERSIST, onTimeOut, base);
        struct timeval tv;
        evutil_timerclear(&tv);
        tv.tv_sec = 1;
        event_add(timeEvent, &tv);
        event_base_dispatch(base);
        event_free(timeEvent);
        event_base_free(base);
        return 0;
}

valgrind --leak-check=full --show-reachable=yes ./a.out
==15543== Memcheck, a memory error detector.
==15543== Copyright (C) 2002-2006, and GNU GPL'd, by Julian Seward et al.
==15543== Using LibVEX rev 1658, a library for dynamic binary translation.
==15543== Copyright (C) 2004-2006, and GNU GPL'd, by OpenWorks LLP.
==15543== Using valgrind-3.2.1, a dynamic binary instrumentation framework.
==15543== Copyright (C) 2000-2006, and GNU GPL'd, by Julian Seward et al.
==15543== For more details, rerun with: -v
==15543==
==15543==
==15543== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 4 from 1)
==15543== malloc/free: in use at exit: 120 bytes in 3 blocks.
==15543== malloc/free: 14 allocs, 11 frees, 1,776 bytes allocated.
==15543== For counts of detected errors, rerun with: -v
==15543== searching for pointers to 3 not-freed blocks.
==15543== checked 206,968 bytes.
==15543==
==15543== 120 bytes in 3 blocks are still reachable in loss record 1 of 1
==15543== at 0x4A05809: malloc (vg_replace_malloc.c:149)
==15543== by 0x4E61ED1: evthread_posix_lock_alloc (evthread_pthread.c:46)
==15543== by 0x4C2AB37: event_global_setup_locks_ (event.c:2894)
==15543== by 0x4E61CE3: evthread_use_pthreads (evthread_pthread.c:187)
==15543== by 0x400A57: main (in /root/dev/a.out)
==15543==
==15543== LEAK SUMMARY:
==15543== definitely lost: 0 bytes in 0 blocks.
==15543== possibly lost: 0 bytes in 0 blocks.
==15543== still reachable: 120 bytes in 3 blocks.
==15543== suppressed: 0 bytes in 0 blocks.

[qidu]

We can add following patches to fix the bug
--------------------------------------------------------------------patch of signal.c------------------------------------------------------------------

--- /root/dev/orig/libevent-2.0.21-stable/signal.c  2012-11-02 23:57:00.000000000 +0800
+++ /root/dev/libevent-2.0.21-stable/signal.c   2013-04-16 15:27:31.000000000 +0800
@@ -439,7 +439,14 @@
 int
 evsig_global_setup_locks_(const int enable_locks)
 {
    EVTHREAD_SETUP_GLOBAL_LOCK(evsig_base_lock, 0);
    return 0;
 }
+
+int
+evsig_global_free_locks_(const int enable_locks)
+{
+   EVTHREAD_FREE_LOCK(evsig_base_lock, 0);
+}
 #endif

--------------------------------------------------------------------patch of evutil_rand.c------------------------------------------------------------------

--- /root/dev/orig/libevent-2.0.21-stable/evutil_rand.c 2012-08-02 23:36:53.000000000 +0800
+++ /root/dev/libevent-2.0.21-stable/evutil_rand.c  2013-04-16 15:27:19.000000000 +0800
@@ -118,9 +118,16 @@
 int
 evutil_secure_rng_global_setup_locks_(const int enable_locks)
 {
    EVTHREAD_SETUP_GLOBAL_LOCK(arc4rand_lock, 0);
    return 0;
 }
+
+int
+evutil_secure_rng_global_free_locks_(const int enable_locks)
+{
+   EVTHREAD_FREE_LOCK(arc4rand_lock, 0);
+}
 #endif

 int

------------------------------------------------------------patch of event.c---------------------------------------------------------------------------------

--- /root/dev/orig/libevent-2.0.21-stable/event.c   2012-11-17 08:22:19.000000000 +0800
+++ /root/dev/libevent-2.0.21-stable/event.c    2013-04-16 15:30:15.000000000 +0800
@@ -788,7 +789,12 @@
    EVTHREAD_FREE_LOCK(base->th_base_lock, EVTHREAD_LOCKTYPE_RECURSIVE);
    EVTHREAD_FREE_COND(base->current_event_cond);

+   if(!current_base) {
+       event_global_free_locks_(0);
+   }
+
    mm_free(base);
 }

 /* reinitialize the event base after a fork */
@@ -2887,6 +2895,16 @@
        return -1;
    return 0;
 }
+
+int 
+event_global_free_locks_(const int enable_locks)
+{
+   evutil_secure_rng_global_free_locks_(0);
+   evsig_global_free_locks_(0);
+#ifndef _EVENT_DISABLE_DEBUG_MODE
+   EVTHREAD_FREE_LOCK(_event_debug_map_lock, 0);
+#endif
+}
 #endif

 void

[nmathewson]

This part is broken:

+   if(!current_base) {
+       event_global_free_locks_(0);
+   }

If someone creates two event_bases, and frees the second one, this will free the global locks.

Libevent 2.1 already has a fix for this in the libevent_global_shutdown() function.

[qidu]

OK, i see, current_base is not a right flag for releasing global locks.
Calling the external interface "libevent_global_shutdown" explicitly would be better for users.
Thanks!