[PATCH 6/7] kernel-shark: Check if "trace_seq" was destroyed before using it

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

When closing a "tep" data stream we destroy the "trace_seq" object.
However, trace_seq_destroy() sets the buffer to "TRACE_SEQ_POISON"
which is different from NULL.

It is unfortunate that TRACE_SEQ_POISON is an internal definition
of libtraceevent, so we have to redefine it here, but this can be
fixed in the future.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 src/libkshark-tepdata.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/libkshark-tepdata.c b/src/libkshark-tepdata.c
index bc5babb..4a84141 100644
--- a/src/libkshark-tepdata.c
+++ b/src/libkshark-tepdata.c
@@ -29,11 +29,17 @@
 #include "libkshark-plugin.h"
 #include "libkshark-tepdata.h"
 
+/**
+ * The TEP_SEQ_POISON is to catch the use of
+ * a trace_seq structure after it was destroyed.
+ */
+#define TEP_SEQ_POISON	((void *)0xdeadbeef)
+
 static __thread struct trace_seq seq;
 
 static bool init_thread_seq(void)
 {
-	if (!seq.buffer)
+	if (!seq.buffer || seq.buffer == TEP_SEQ_POISON)
 		trace_seq_init(&seq);
 
 	return seq.buffer != NULL;
-- 
2.27.0