clayborg wrote:
So the issue from only the lldb-dap side here is VS Code is sending a threads
request, but we have resumed the process upon attach after sending the
configuration done request. So the race condition happens like:
- send configuration done
- send continue to process if stop on entry if false
- <start race condition>
- Our event thread will at some point consume the `eStateRunning` and cause
our public API to not allow stop locker requests to succeed, but any API calls
that come through before we consume this event will succeed,
- at the same time as the above event thread, we get a "threads" request and
start calling `SBProcess::GetNumThreads()` and
`SBProcess::GetThreadAtIndex(...)` and might get valid results if the run
locker is allowing stopped process calls. so we may start getting the number of
threads and some threads by index, but any of these calls can fail as soon as
we consume the `eStateRunning` process event in lldb-dap
So from a DAP only perspective, we need to sync with our lldb-dap event thread.
Current code looks like:
```
void ConfigurationDoneRequestHandler::operator()(
const llvm::json::Object &request) const {
llvm::json::Object response;
FillResponse(request, response);
dap.SendJSON(llvm::json::Value(std::move(response)));
dap.configuration_done_sent = true;
if (dap.stop_at_entry)
SendThreadStoppedEvent(dap);
else
dap.target.GetProcess().Continue();
}
```
But probably should look like:
```
void ConfigurationDoneRequestHandler::operator()(
const llvm::json::Object &request) const {
llvm::json::Object response;
FillResponse(request, response);
dap.SendJSON(llvm::json::Value(std::move(response)));
dap.configuration_done_sent = true;
if (dap.stop_at_entry)
SendThreadStoppedEvent(dap);
else {
dap.target.GetProcess().Continue();
dap.WaitForProcessResumedEvent(); /// New sync point here!
}
}
```
The call to `dap.WaitForProcessResumedEvent()` will make sure we have received
the `eStateRunning` process event before continuing. Then the "threads" call
can fail as the process stop locker won't succeed for the
`SBProcess::GetNumThreads()` and `SBProcess::GetThreadAtIndex(....)` calls.
Once we get past this race, we are good, but again, only from the DAP
perspective.
The fact that GetNumThreads() is able to interrupt (send a CTRL+C) to the
lldb-server is another bug that needs fixing. I thought that only the
breakpoint setting code would interrupt a process and send GDB remote packets
while running. Why are we allowing the threads request to interrupt?
https://github.com/llvm/llvm-project/pull/134339
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