The attached patch works around the issue. The problem is
the tracepoint destructors that run in parallel with the thread
that still exists.
If we remove this, we leak the liblttng-ust-tracepoint.so.0 shared
object on dlclose of the instrumented code. Not sure if we should
care though...
Thoughts ?
Thanks,
Mathieu
----- On Mar 8, 2016, at 7:35 PM, Mathieu Desnoyers
<mathieu.desnoy...@efficios.com> wrote:
> Reproduced it on master (ust and tools).
> Repro with:
> lttng create
> lttng enable-event -u -a
> lttng start
> then run hello a few times, it eventually segfaults in the spawned thread.
> Looking into it.
> Thanks,
> Mathieu
> ----- On Mar 8, 2016, at 7:12 PM, Jonathan Rajotte Julien
> <jonathan.rajotte-jul...@efficios.com> wrote:
>> Hi Jeffrey,
>> Could you provide the version for lttng-ust, lttng-tools, lttng-modules (if
>> installed)?
>> Were you able to reproduce the issue on master (git) ?
>> What are the exact order of command to reproduce the problem ?
>> Thanks
>> On 2016-03-08 06:43 PM, Jeffrey Chen wrote:
>>> Hi LTTng community:
>>> We are using LTTng for our production environment. We have been noticing
>>> segfault problem when our process exit. We think the problem is due to the
>>> background thread continue to write traces, while LTTng cleanup its memory.
>>> We
>>> do not know how to fix this issue without changing LTTng code base. I have
>>> written a very simple app that could repro the problem. Most of my codes are
>>> copy pasted from the LTTng doc sample. Is there any fix that the LTTng side
>>> could do?
>>> hello.c
>>> #include <stdio.h>
>>> #include "hello-tp.h"
>>> #include <pthread.h>
>>> void* doSomeThing(void *arg)
>>> {
>>> int x;
>>> for (x = 0; x < 100000; ++x) {
>>> tracepoint(hello_world, my_first_tracepoint, x, "test");
>>> }
>>> }
>>> int main(int argc, char *argv[])
>>> {
>>> int x;
>>> getchar();
>>> pthread_t inc_x_thread;
>>> if(pthread_create(&inc_x_thread, NULL, doSomeThing, NULL)) {
>>> fprintf(stderr, "Error creating thread\n");
>>> return 1;
>>> }
>>> tracepoint(hello_world, my_first_tracepoint, 23, "hi there!");
>>> return 0;
>>> }
>>> hello-tp.c
>>> #define TRACEPOINT_CREATE_PROBES
>>> #define TRACEPOINT_DEFINE
>>> #include "hello-tp.h"
>>> hello-tp.h
>>> #undef TRACEPOINT_PROVIDER
>>> #define TRACEPOINT_PROVIDER hello_world
>>> #undef TRACEPOINT_INCLUDE
>>> #define TRACEPOINT_INCLUDE "./hello-tp.h"
>>> #if !defined(_HELLO_TP_H) || defined(TRACEPOINT_HEADER_MULTI_READ)
>>> #define _HELLO_TP_H
>>> #include <lttng/tracepoint.h>
>>> TRACEPOINT_EVENT(
>>> hello_world,
>>> my_first_tracepoint,
>>> TP_ARGS(
>>> int, my_integer_arg,
>>> char*, my_string_arg
>>> ),
>>> TP_FIELDS(
>>> ctf_string(my_string_field, my_string_arg)
>>> ctf_integer(int, my_integer_field, my_integer_arg)
>>> )
>>> )
>>> #endif /* _HELLO_TP_H */
>>> #include <lttng/tracepoint-event.h>
>>> Compile
>>> gcc -c -I. hello-tp.c
>>> gcc -c hello.c
>>> gcc -o hello hello.o hello-tp.o -llttng-ust -ldl -lpthread
>>> _______________________________________________
>>> lttng-dev mailing list lttng-dev@lists.lttng.org
>>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>> --
>> Jonathan R. Julien
>> Efficios
>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev@lists.lttng.org
>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
commit fcf3b4b09fa4558014328f34b0a1c396a03b6515
Author: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
Date: Tue Mar 8 21:05:32 2016 -0500
Workaround
diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
index 16348b8..d9e2003 100644
--- a/include/lttng/tracepoint.h
+++ b/include/lttng/tracepoint.h
@@ -301,6 +301,7 @@ __tracepoints__destroy(void)
if (--__tracepoint_registered)
return;
+#if 0
if (tracepoint_dlopen.liblttngust_handle && !__tracepoint_ptrs_registered) {
ret = dlclose(tracepoint_dlopen.liblttngust_handle);
if (ret) {
@@ -309,6 +310,7 @@ __tracepoints__destroy(void)
}
memset(&tracepoint_dlopen, 0, sizeof(tracepoint_dlopen));
}
+#endif
}
#endif
@@ -404,6 +406,7 @@ __tracepoints__ptrs_destroy(void)
if (--__tracepoint_ptrs_registered)
return;
+#if 0
if (tracepoint_dlopen.tracepoint_unregister_lib)
tracepoint_dlopen.tracepoint_unregister_lib(__start___tracepoints_ptrs);
if (tracepoint_dlopen.liblttngust_handle && !__tracepoint_registered) {
@@ -414,6 +417,7 @@ __tracepoints__ptrs_destroy(void)
}
memset(&tracepoint_dlopen, 0, sizeof(tracepoint_dlopen));
}
+#endif
}
#else /* TRACEPOINT_DEFINE */
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