From: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Date: Tue, 3 Jul 2018 16:28:54 +0000 (-0400)
Subject: Use trace->trace_id in check to remove trace from bt_ctx
X-Git-Tag: v1.5.6~2
X-Git-Url: http://git.efficios.com/?p=babeltrace.git;a=commitdiff_plain;h=c8a683194ae8caef6592cd235bf1666001d8d4cd

Use trace->trace_id in check to remove trace from bt_ctx

Commit b9e6498df8b3e7c2ad312dccddf9f1a5e181648e removes the existence
guarantee of the trace_id hash table key by moving the trace->in_use
assignation before the assignation of trace_id and insertion into the
hash table.

Use the trade_id field value to validate if it should be removed from
the hash table. A NULL trace_id field indicates that no insertion was
performed.

This is mostly a workaround to a problem found in, at least, glib 2.28
where g_hash_table_lookup_node() aborts on a SIGFPE signal due to
modulo by zero. The exact cause for this is unknown for now, but a
similar problem was reported against Nautilus [1].

There is little reason for "mod" to be 0 at that point, as explained
in the bug report.

Currently unable to reproduce.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1074401

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/formats/lttng-live/lttng-live-comm.c b/formats/lttng-live/lttng-live-comm.c
index 055b1c30..ec03fb2f 100644
--- a/formats/lttng-live/lttng-live-comm.c
+++ b/formats/lttng-live/lttng-live-comm.c
@@ -390,6 +390,7 @@ int lttng_live_ctf_trace_assign(struct lttng_live_viewer_stream *stream,
 	if (!trace) {
 		trace = g_new0(struct lttng_live_ctf_trace, 1);
 		trace->ctf_trace_id = ctf_trace_id;
+		trace->trace_id = -1;
 		printf_verbose("Create trace ctf_trace_id %" PRIu64 "\n", ctf_trace_id);
 		BT_INIT_LIST_HEAD(&trace->stream_list);
 		g_hash_table_insert(stream->session->ctf_traces,
@@ -1466,7 +1467,7 @@ int del_traces(gpointer key, gpointer value, gpointer user_data)
 		lvstream->in_trace = 0;
 		bt_list_del(&lvstream->trace_stream_node);
 	}
-	if (trace->in_use) {
+	if (trace->in_use && trace->trace_id >= 0) {
 		ret = bt_context_remove_trace(bt_ctx, trace->trace_id);
 		if (ret < 0)
 			fprintf(stderr, "[error] removing trace from context\n");
diff --git a/formats/lttng-live/lttng-live.h b/formats/lttng-live/lttng-live.h
index 9739078a..34c57ede 100644
--- a/formats/lttng-live/lttng-live.h
+++ b/formats/lttng-live/lttng-live.h
@@ -88,6 +88,7 @@ struct lttng_live_ctf_trace {
 	struct bt_list_head stream_list;
 	FILE *metadata_fp;
 	struct bt_trace_handle *handle;
+	/* Set to -1 when not initialized. */
 	int trace_id;
 	int in_use;
 };