Fix: sessiond: snapshot: leak of trace chunk

Valgrind reports a leak after every snapshot record command:

==827791== 430 (280 direct, 150 indirect) bytes in 1 blocks are definitely lost in loss record 34 of 37
==827791==    at 0x48435FF: calloc (vg_replace_malloc.c:1117)
==827791==    by 0x223D01: zmalloc (macros.h:45)
==827791==    by 0x224B79: lttng_trace_chunk_allocate (trace-chunk.c:387)
==827791==    by 0x224E41: lttng_trace_chunk_create (trace-chunk.c:427)
==827791==    by 0x150B55: session_create_new_trace_chunk (session.c:656)
==827791==    by 0x164A11: snapshot_record (cmd.c:5113)
==827791==    by 0x1651EE: cmd_snapshot_record (cmd.c:5302)
==827791==    by 0x196E74: process_client_msg (client.c:2166)
==827791==    by 0x198AF1: thread_manage_clients (client.c:2742)
==827791==    by 0x18E245: launch_thread (thread.c:66)
==827791==    by 0x4B9E258: start_thread (in /usr/lib/libpthread-2.33.so)
==827791==    by 0x4CB45E2: clone (in /usr/lib/libc-2.33.so)

session_set_trace_chunk() on line 5162 returns a reference to the
current trace chunk which is never released.

This also causes tests/regression/tools/snapshots/test_ust_long to fail
due to a file descriptor exhaustion (presumably from using too many
directory file descriptors) when it is executed by an unprivileged user.

The CI doesn't catch this since the long regression test suite is
executed as root.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I4b6e45df48c3daafa2294c80ccd8a2b4d91401e1

diff --git a/src/bin/lttng-sessiond/cmd.cpp b/src/bin/lttng-sessiond/cmd.cpp
index 6bdfe30c161ecbab118f8a9bcdae8c8c28f8304d..b4bd6b43fca8826850a83d4f0fd6b0ec4579b735 100644 (file)
--- a/src/bin/lttng-sessiond/cmd.cpp
+++ b/src/bin/lttng-sessiond/cmd.cpp
@@ -5176,6 +5176,9 @@ error_close_trace_chunk:
                                session->name);
                ret_code = LTTNG_ERR_CLOSE_TRACE_CHUNK_FAIL_CONSUMER;
        }
                                session->name);
                ret_code = LTTNG_ERR_CLOSE_TRACE_CHUNK_FAIL_CONSUMER;
        }

+
+       lttng_trace_chunk_put(snapshot_trace_chunk);
+       snapshot_trace_chunk = NULL;

 error:
        if (original_ust_consumer_output) {
                session->ust_session->consumer = original_ust_consumer_output;
 error:
        if (original_ust_consumer_output) {
                session->ust_session->consumer = original_ust_consumer_output;