2 files changed, 22 insertions, 0 deletions
diff --git a/library/std/src/sys_common/once/futex.rs b/library/std/src/sys_common/once/futex.rs
index 5c7e6c013..42db5fad4 100644
--- a/library/std/src/sys_common/once/futex.rs
+++ b/library/std/src/sys_common/once/futex.rs
@@ -4,6 +4,7 @@ use crate::sync::atomic::{
     AtomicU32,
     Ordering::{Acquire, Relaxed, Release},
 };
+use crate::sync::once::ExclusiveState;
 use crate::sys::futex::{futex_wait, futex_wake_all};
 
 // On some platforms, the OS is very nice and handles the waiter queue for us.
@@ -78,6 +79,16 @@ impl Once {
         self.state.load(Acquire) == COMPLETE
     }
 
+    #[inline]
+    pub(crate) fn state(&mut self) -> ExclusiveState {
+        match *self.state.get_mut() {
+            INCOMPLETE => ExclusiveState::Incomplete,
+            POISONED => ExclusiveState::Poisoned,
+            COMPLETE => ExclusiveState::Complete,
+            _ => unreachable!("invalid Once state"),
+        }
+    }
+
     // This uses FnMut to match the API of the generic implementation. As this
     // implementation is quite light-weight, it is generic over the closure and
     // so avoids the cost of dynamic dispatch.
diff --git a/library/std/src/sys_common/once/queue.rs b/library/std/src/sys_common/once/queue.rs
index d953a6745..def0bcd6f 100644
--- a/library/std/src/sys_common/once/queue.rs
+++ b/library/std/src/sys_common/once/queue.rs
@@ -60,6 +60,7 @@ use crate::fmt;
 use crate::ptr;
 use crate::sync as public;
 use crate::sync::atomic::{AtomicBool, AtomicPtr, Ordering};
+use crate::sync::once::ExclusiveState;
 use crate::thread::{self, Thread};
 
 type Masked = ();
@@ -121,6 +122,16 @@ impl Once {
         self.state_and_queue.load(Ordering::Acquire).addr() == COMPLETE
     }
 
+    #[inline]
+    pub(crate) fn state(&mut self) -> ExclusiveState {
+        match self.state_and_queue.get_mut().addr() {
+            INCOMPLETE => ExclusiveState::Incomplete,
+            POISONED => ExclusiveState::Poisoned,
+            COMPLETE => ExclusiveState::Complete,
+            _ => unreachable!("invalid Once state"),
+        }
+    }
+
     // This is a non-generic function to reduce the monomorphization cost of
     // using `call_once` (this isn't exactly a trivial or small implementation).
     //