Add an android version of perf's futex-contention script

This is temporarily added here, its not used by androdeb yet.

This will be made a part of androdeb's perf and then once its ready, it
can be submitted to the Linux kernel upstream and deleted from here.

TODO:
  - Add max to statistic print
  - Add support to detect wakers

  - Turn into a new perf script that's android specific (?)
  - Add a flag for android locking selection
  - Add support for pthread lock contention

Signed-off-by: Joel Fernandes <joel@joelfernandes.org>
diff --git a/bcc/misc/futex-contention.py b/bcc/misc/futex-contention.py
new file mode 100644
index 0000000..5c96780
--- /dev/null
+++ b/bcc/misc/futex-contention.py
@@ -0,0 +1,63 @@
+# futex contention
+# (c) 2010, Arnaldo Carvalho de Melo <acme@redhat.com>
+# Licensed under the terms of the GNU GPL License version 2
+#
+# Translation of:
+#
+# http://sourceware.org/systemtap/wiki/WSFutexContention
+#
+# to perf python scripting.
+#
+# Measures futex contention
+
+import os, sys
+sys.path.append(os.environ['PERF_EXEC_PATH'] + '/scripts/python/Perf-Trace-Util/lib/Perf/Trace')
+from Util import *
+
+process_names = {}
+thread_thislock = {}
+thread_blocktime = {}
+
+lock_waits = {} # long-lived stats on (tid,lock) blockage elapsed time
+process_names = {} # long-lived pid-to-execname mapping
+
+def android_lock(callchain):
+    for c in callchain:
+        if 'sym' in c and 'name' in c['sym']:
+            name = c['sym']['name']
+        else:
+            continue
+
+        if 'art::Monitor::Lock' in name:
+            return True
+    return False
+
+def syscalls__sys_enter_futex(event, ctxt, cpu, s, ns, tid, comm, callchain,
+			      nr, uaddr, op, val, utime, uaddr2, val3):
+
+	cmd = op & FUTEX_CMD_MASK
+        if cmd != FUTEX_WAIT or android_lock(callchain) == False:
+		return # we don't care about originators of WAKE events 
+                       # or futex uses that aren't android locks.
+
+	process_names[tid] = comm
+	thread_thislock[tid] = uaddr
+	thread_blocktime[tid] = nsecs(s, ns)
+
+def syscalls__sys_exit_futex(event, ctxt, cpu, s, ns, tid, comm, callchain,
+			     nr, ret):
+	if thread_blocktime.has_key(tid):
+		elapsed = nsecs(s, ns) - thread_blocktime[tid]
+		add_stats(lock_waits, (tid, thread_thislock[tid]), elapsed)
+		del thread_blocktime[tid]
+		del thread_thislock[tid]
+
+def trace_begin():
+	print "Press control+C to stop and show the summary"
+
+def trace_end():
+	for (tid, lock) in lock_waits:
+		min, max, avg, count = lock_waits[tid, lock]
+		print "%s[%d] lock %x contended %d times, %d avg ns" % \
+		      (process_names[tid], tid, lock, count, avg)
+