std: send free message when xous thread parker is dropped

Author: joboet

library/std/src/sys/xous/thread_parking.rs

@@ -1,4 +1,4 @@
-use crate::os::xous::ffi::blocking_scalar;
+use crate::os::xous::ffi::{blocking_scalar, scalar};
 use crate::os::xous::services::{ticktimer_server, TicktimerScalar};
 use crate::pin::Pin;
 use crate::ptr;
@@ -86,3 +86,9 @@ impl Parker {
         }
     }
 }
+
+impl Drop for Parker {
+    fn drop(&mut self) {
+        scalar(ticktimer_server(), TicktimerScalar::FreeCondition(self.index()).into()).ok();
+    }
+}