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trace/systrace: make start() return when tracing has started

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In SystraceCollector, start() returns after executing
subprocess.Popen() for systrace. That doesn't mean that systrace is
running though, the function can return even before systrace has had a
chance to execute anything. Therefore, when you run the command
you want to trace, systrace will miss the first seconds of the
execution.

Run systrace with -u to unbuffer its stdin and wait for it to print
"Starting tracing (stop with enter)" before returning.

Fixes #403
This commit is contained in:
Javi Merino 2019-07-30 14:43:58 +01:00 committed by Marc Bonnici
parent 986261bc7e
commit 71bd8b10ed
1 changed files with 3 additions and 1 deletions
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4
devlib/trace/systrace.py
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@ -107,7 +107,7 @@ class SystraceCollector(TraceCollector):
self._tmpfile = NamedTemporaryFile()
# pylint: disable=attribute-defined-outside-init
self.systrace_cmd = '{} -o {} -e {}'.format(
self.systrace_cmd = 'python2 -u {} -o {} -e {}'.format(
self.systrace_binary,
self._tmpfile.name,
self.target.adb_name
@ -137,9 +137,11 @@ class SystraceCollector(TraceCollector):
self._systrace_process = subprocess.Popen(
self.systrace_cmd,
stdin=subprocess.PIPE,
stdout=subprocess.PIPE,
shell=True,
universal_newlines=True
)
self._systrace_process.stdout.read(1)
def stop(self):
if not self._systrace_process: