1 files changed, 21 insertions, 12 deletions
diff --git a/catapult/systrace/systrace/tracing_agents/atrace_agent.py b/catapult/systrace/systrace/tracing_agents/atrace_agent.py
index f699fc05..caf78f44 100644
--- a/catapult/systrace/systrace/tracing_agents/atrace_agent.py
+++ b/catapult/systrace/systrace/tracing_agents/atrace_agent.py
@@ -241,19 +241,28 @@ class AtraceAgent(tracing_agents.TracingAgent):
   def _stop_collect_trace(self):
     """Stops atrace.
 
-    Note that prior to Api 23, --async-stop may not actually stop tracing.
-    Thus, this uses a fallback method of running a zero-length synchronous
-    trace if tracing is still on."""
-    result = self._device_utils.RunShellCommand(
-        self._tracer_args + ['--async_stop'], raw_output=True,
-        large_output=True, check_return=True, timeout=ADB_LARGE_OUTPUT_TIMEOUT)
-    is_trace_enabled_file = '/sys/kernel/debug/tracing/tracing_on'
-
+    Note that prior to Api 23, --async-stop isn't working correctly. It
+    doesn't stop tracing and clears trace buffer before dumping it rendering
+    results unusable."""
     if self._device_sdk_version < version_codes.MARSHMALLOW:
-      if int(self._device_utils.ReadFile(is_trace_enabled_file)):
-        # tracing was incorrectly left on, disable it
-        self._device_utils.RunShellCommand(
-            self._tracer_args + ['-t 0'], check_return=True)
+      is_trace_enabled_file = '/sys/kernel/debug/tracing/tracing_on'
+      # Stop tracing first so new data won't arrive while dump is performed (it
+      # may take a non-trivial time and tracing buffer may overflow).
+      self._device_utils.WriteFile(is_trace_enabled_file, '0')
+      result = self._device_utils.RunShellCommand(
+          self._tracer_args + ['--async_dump'], raw_output=True,
+          large_output=True, check_return=True,
+          timeout=ADB_LARGE_OUTPUT_TIMEOUT)
+      # Run synchronous tracing for 0 seconds to stop tracing, clear buffers
+      # and other state.
+      self._device_utils.RunShellCommand(
+          self._tracer_args + ['-t 0'], check_return=True)
+    else:
+      # On M+ --async_stop does everything necessary
+      result = self._device_utils.RunShellCommand(
+          self._tracer_args + ['--async_stop'], raw_output=True,
+          large_output=True, check_return=True,
+          timeout=ADB_LARGE_OUTPUT_TIMEOUT)
 
     return result