Kernel: Prevent deadlocks when panicking

moon/src/panic.rs

@@ -1,9 +1,12 @@
 use core::panic::PanicInfo;
 
-use crate::println;
+use crate::try_println;
+use crate::arch::io::SERIAL;
+use crate::arch::cpu;
 
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
-    println!("Kernel {}", info);
-    loop {}
+    unsafe { SERIAL.force_unlock(); } // since we're panicking, this is not relevant anymore.
+    try_println!("Kernel {}", info); // we probably should succeed, unless another CPU locked the serial port just after we unlocked it but before try_println attempts to lock it.
+    cpu::halt();
 }