examples/tracing: some minor fixes

- chmod +x dddos.py mallocstacks.py stack_buildid_example.py
- Handle Ctrl-C keyboard interrupt for dddos.py, disksnoop.py,
  hello_perf_output.py, stacksnoop.py and trace_perf_output.py

examples/tracing/dddos.py

@@ -99,4 +99,7 @@ def trigger_alert_event(cpu, data, size):
 # loop with callback to trigger_alert_event
 b["events"].open_perf_buffer(trigger_alert_event)
 while 1:
-    b.perf_buffer_poll()
+    try:
+        b.perf_buffer_poll()
+    except KeyboardInterrupt:
+        exit()

examples/tracing/disksnoop.py

@@ -51,15 +51,18 @@ print("%-18s %-2s %-7s %8s" % ("TIME(s)", "T", "BYTES", "LAT(ms)"))
 
 # format output
 while 1:
-	(task, pid, cpu, flags, ts, msg) = b.trace_fields()
-	(bytes_s, bflags_s, us_s) = msg.split()
+	try:
+		(task, pid, cpu, flags, ts, msg) = b.trace_fields()
+		(bytes_s, bflags_s, us_s) = msg.split()
 
-	if int(bflags_s, 16) & REQ_WRITE:
-		type_s = "W"
-	elif bytes_s == "0":	# see blk_fill_rwbs() for logic
-		type_s = "M"
-	else:
-		type_s = "R"
-	ms = float(int(us_s, 10)) / 1000
+		if int(bflags_s, 16) & REQ_WRITE:
+			type_s = "W"
+		elif bytes_s == "0":	# see blk_fill_rwbs() for logic
+			type_s = "M"
+		else:
+			type_s = "R"
+		ms = float(int(us_s, 10)) / 1000
 
-	print("%-18.9f %-2s %-7s %8.2f" % (ts, type_s, bytes_s, ms))
+		print("%-18.9f %-2s %-7s %8.2f" % (ts, type_s, bytes_s, ms))
+	except KeyboardInterrupt:
+		exit()

examples/tracing/hello_perf_output.py

@@ -58,4 +58,7 @@ def print_event(cpu, data, size):
 # loop with callback to print_event
 b["events"].open_perf_buffer(print_event)
 while 1:
-    b.perf_buffer_poll()
+    try:
+        b.perf_buffer_poll()
+    except KeyboardInterrupt:
+        exit()

examples/tracing/stacksnoop.py

@@ -120,4 +120,7 @@ def print_event(cpu, data, size):
 
 b["events"].open_perf_buffer(print_event)
 while 1:
-    b.perf_buffer_poll()
+    try:
+        b.perf_buffer_poll()
+    except KeyboardInterrupt:
+        exit()

examples/tracing/trace_perf_output.py

@@ -53,4 +53,7 @@ def print_counter():
 print("Tracing " + event_name + ", try `dd if=/dev/zero of=/dev/null`")
 print("Tracing... Hit Ctrl-C to end.")
 while 1:
-    b.perf_buffer_poll()
+    try:
+        b.perf_buffer_poll()
+    except KeyboardInterrupt:
+        exit()