check whether pinning to the OS thread fixes the issue

internal/libtor/enabled.go

@@ -149,6 +149,13 @@ var ErrNonzeroExitCode = errors.New("libtor: command completed with nonzero exit
 // runtor runs tor until completion and ensures that tor exits when
 // the given ctx is cancelled or its deadline expires.
 func (p *torProcess) runtor(ctx context.Context, cc net.Conn, args ...string) {
+ // make sure we lock to an OS thread otherwise the goroutine can get
+ // preempted midway and cause data races
+ //
+ // See https://github.com/ooni/probe/issues/2406#issuecomment-1479138677
+ runtime.LockOSThread()
+ defer runtime.UnlockOSThread()
+
  // wait for Start or context to expire
  select {
  case <-p.awaitStart: