Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/tools/perf/scripts/python/stackcollapse.py b/tools/perf/scripts/python/stackcollapse.py
index 1697b5e..b1c4def 100755
--- a/tools/perf/scripts/python/stackcollapse.py
+++ b/tools/perf/scripts/python/stackcollapse.py
@@ -19,13 +19,15 @@
 # Written by Paolo Bonzini <pbonzini@redhat.com>
 # Based on Brendan Gregg's stackcollapse-perf.pl script.
 
+from __future__ import print_function
+
 import os
 import sys
 from collections import defaultdict
 from optparse import OptionParser, make_option
 
 sys.path.append(os.environ['PERF_EXEC_PATH'] + \
-                '/scripts/python/Perf-Trace-Util/lib/Perf/Trace')
+    '/scripts/python/Perf-Trace-Util/lib/Perf/Trace')
 
 from perf_trace_context import *
 from Core import *
@@ -120,7 +122,6 @@
     lines[stack_string] = lines[stack_string] + 1
 
 def trace_end():
-    list = lines.keys()
-    list.sort()
+    list = sorted(lines)
     for stack in list:
-        print "%s %d" % (stack, lines[stack])
+        print("%s %d" % (stack, lines[stack]))