[Lldb-commits] [PATCH] D83446: [WIP][lldb/Reproducers] Synchronize the command interpreter with asynchronous events

[Pavel Labath via Phabricator via lldb-commits]

labath added a reviewer: jingham.
labath added a comment.

Well, this is an interesting problem... IIUC, what's happening is that the printing of the "stop reason" in the "event handler thread" is generating some packets (to fetch the stop reason), and then the "cont" command produces some (c) too...

I'm wondering if this problem does not go beyond reproducers... The fact that we can have two threads running in parallel, doing stuff, without much synchronization seems like a bad idea in general. In theory, something similar could happen during normal operation as well, if the user was fast enough to type "cont<Return>" before the stop reason is printed. In the non-reproducer mode we wouldn't crash with the unexpected packet assertion, but we would probably do something unexpected nonetheless. Of course, a real human user won't be fast enough to do that, but I wouldn't rule out this being the cause of the flakiness of some of our pexpect tests. And I'm not sure what happens when sourcing command files, which is fairly similar to running a reproducer. How would the events be processed there?

So, I'm wondering if we shouldn't add some form of synchronization here, which would be independent of the reproducer mode we're running in. That would solve the reproducer problem as a consequence, but it seems like it would be generally useful. One way to do that could be to send some sort of a ping event (EventDataReceipt ?) to the event handler thread before or after running a command, and wait for it to report back. That should ensure that all events produced by the previous command have been fully processed...


Repository:
  rLLDB LLDB

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https://reviews.llvm.org/D83446