warning: thread support is experimental: the scheduler is not preemptive, and can get stuck in spin loops.
         (see https://github.com/rust-lang/miri/issues/1388)

Thread 1 starting, will block on mutex
Thread 1 reported it has started
thread '<unnamed>' panicked at 'panic in thread 2', $DIR/concurrent-panic.rs:LL:CC
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Thread 2 blocking on thread 1
Thread 2 reported it has started
Unlocking mutex
thread '<unnamed>' panicked at 'panic in thread 1', $DIR/concurrent-panic.rs:LL:CC
Thread 1 has exited
Thread 2 has exited