How to find all occurrences where main thread waited on lock held by background thread in a Android Profiler output

Question

My application uses background thread to initialize some of the stuff required by main thread to load the hero activity. It has bunch of locks for synchronization. I am looking for a quick way to plot possible stack traces where main thread was waiting for lock held by background thread during app startup. I checked Thread Status Monitor. How do I debug this? What's causing it? but this is talking about point to time thread state where as I am looking for all such events that occurred during startup without knowing where those occured.

I do see that this information can be found by manually inspecting startup android profile trace and looking at various thread stacks to find these occurrences, but there is lot of data to go through. It would be great if the tool can just show me # of times main thread waited for lock held by other threads, total amount of time spent and places where it held those locks.

Q1) Do we know whether Android profiler can show this? I checked https://developer.android.com/studio/profile/cpu-profiler but couldn't find it.

Q2) If not, is there any other tool that can parse profiler exported trace and print this info?

Q3) If not, do you have any pointers on how to read exported trace file. It seems to be binary. I am going through https://github.com/JetBrains/android to figure it out. It seems to be using perfetto now, but I haven't been able to write any utility to read that data yet.

Update: I discovered that CPU profiling/Systrace option shows that my main thread does remain idle or waits for some resources, however it doesn't have information around what does it wait for or what methods run after it was idle for some time. Any pointers to how to marry java method traces and sys trace view?

Answer 1

Perfetto is able to show this information. Look for "Lock Contention" messages on the timeline for a given thread. It also prints the data which thread has obtained that lock.