diff --git a/compiler/rustc_data_structures/src/marker.rs b/compiler/rustc_data_structures/src/marker.rs
index b067f9d4502df..41c08fa4d0e5d 100644
--- a/compiler/rustc_data_structures/src/marker.rs
+++ b/compiler/rustc_data_structures/src/marker.rs
@@ -171,7 +171,6 @@ cfg_if!(
             [Vec<T, A> where T: DynSync, A: std::alloc::Allocator + DynSync]
             [Box<T, A> where T: ?Sized + DynSync, A: std::alloc::Allocator + DynSync]
             [crate::sync::RwLock<T> where T: DynSend + DynSync]
-            [crate::sync::OneThread<T> where T]
             [crate::sync::WorkerLocal<T> where T: DynSend]
             [crate::intern::Interned<'a, T> where 'a, T: DynSync]
             [crate::tagged_ptr::CopyTaggedPtr<P, T, CP> where P: Sync + crate::tagged_ptr::Pointer, T: Sync + crate::tagged_ptr::Tag, const CP: bool]
diff --git a/compiler/rustc_data_structures/src/sync.rs b/compiler/rustc_data_structures/src/sync.rs
index cca043ba0d18d..481bff03adc9a 100644
--- a/compiler/rustc_data_structures/src/sync.rs
+++ b/compiler/rustc_data_structures/src/sync.rs
@@ -43,7 +43,6 @@
 pub use crate::marker::*;
 use std::collections::HashMap;
 use std::hash::{BuildHasher, Hash};
-use std::ops::{Deref, DerefMut};
 
 mod lock;
 pub use lock::{Lock, LockGuard, Mode};
@@ -303,8 +302,6 @@ cfg_if! {
 
         use parking_lot::RwLock as InnerRwLock;
 
-        use std::thread;
-
         /// This makes locks panic if they are already held.
         /// It is only useful when you are running in a single thread
         const ERROR_CHECKING: bool = false;
@@ -439,56 +436,3 @@ impl<T: Clone> Clone for RwLock<T> {
         RwLock::new(self.borrow().clone())
     }
 }
-
-/// A type which only allows its inner value to be used in one thread.
-/// It will panic if it is used on multiple threads.
-#[derive(Debug)]
-pub struct OneThread<T> {
-    #[cfg(parallel_compiler)]
-    thread: thread::ThreadId,
-    inner: T,
-}
-
-#[cfg(parallel_compiler)]
-unsafe impl<T> std::marker::Sync for OneThread<T> {}
-#[cfg(parallel_compiler)]
-unsafe impl<T> std::marker::Send for OneThread<T> {}
-
-impl<T> OneThread<T> {
-    #[inline(always)]
-    fn check(&self) {
-        #[cfg(parallel_compiler)]
-        assert_eq!(thread::current().id(), self.thread);
-    }
-
-    #[inline(always)]
-    pub fn new(inner: T) -> Self {
-        OneThread {
-            #[cfg(parallel_compiler)]
-            thread: thread::current().id(),
-            inner,
-        }
-    }
-
-    #[inline(always)]
-    pub fn into_inner(value: Self) -> T {
-        value.check();
-        value.inner
-    }
-}
-
-impl<T> Deref for OneThread<T> {
-    type Target = T;
-
-    fn deref(&self) -> &T {
-        self.check();
-        &self.inner
-    }
-}
-
-impl<T> DerefMut for OneThread<T> {
-    fn deref_mut(&mut self) -> &mut T {
-        self.check();
-        &mut self.inner
-    }
-}
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index b484978eed230..f0a513c8cda4d 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -17,7 +17,8 @@ use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::jobserver::{self, Client};
 use rustc_data_structures::profiling::{duration_to_secs_str, SelfProfiler, SelfProfilerRef};
 use rustc_data_structures::sync::{
-    AtomicU64, AtomicUsize, Lock, Lrc, OneThread, Ordering, Ordering::SeqCst,
+    AtomicU64, AtomicUsize, Lock, Lrc, MappedReadGuard, Ordering, Ordering::SeqCst, ReadGuard,
+    RwLock,
 };
 use rustc_errors::annotate_snippet_emitter_writer::AnnotateSnippetEmitterWriter;
 use rustc_errors::emitter::{DynEmitter, EmitterWriter, HumanReadableErrorType};
@@ -39,7 +40,6 @@ use rustc_target::spec::{
     DebuginfoKind, SanitizerSet, SplitDebuginfo, StackProtector, Target, TargetTriple, TlsModel,
 };
 
-use std::cell::{self, RefCell};
 use std::env;
 use std::fmt;
 use std::ops::{Div, Mul};
@@ -152,7 +152,7 @@ pub struct Session {
     /// Input, input file path and output file path to this compilation process.
     pub io: CompilerIO,
 
-    incr_comp_session: OneThread<RefCell<IncrCompSession>>,
+    incr_comp_session: RwLock<IncrCompSession>,
     /// Used for incremental compilation tests. Will only be populated if
     /// `-Zquery-dep-graph` is specified.
     pub cgu_reuse_tracker: CguReuseTracker,
@@ -853,9 +853,9 @@ impl Session {
         *incr_comp_session = IncrCompSession::InvalidBecauseOfErrors { session_directory };
     }
 
-    pub fn incr_comp_session_dir(&self) -> cell::Ref<'_, PathBuf> {
+    pub fn incr_comp_session_dir(&self) -> MappedReadGuard<'_, PathBuf> {
         let incr_comp_session = self.incr_comp_session.borrow();
-        cell::Ref::map(incr_comp_session, |incr_comp_session| match *incr_comp_session {
+        ReadGuard::map(incr_comp_session, |incr_comp_session| match *incr_comp_session {
             IncrCompSession::NotInitialized => panic!(
                 "trying to get session directory from `IncrCompSession`: {:?}",
                 *incr_comp_session,
@@ -868,7 +868,7 @@ impl Session {
         })
     }
 
-    pub fn incr_comp_session_dir_opt(&self) -> Option<cell::Ref<'_, PathBuf>> {
+    pub fn incr_comp_session_dir_opt(&self) -> Option<MappedReadGuard<'_, PathBuf>> {
         self.opts.incremental.as_ref().map(|_| self.incr_comp_session_dir())
     }
 
@@ -1460,7 +1460,7 @@ pub fn build_session(
         parse_sess,
         sysroot,
         io,
-        incr_comp_session: OneThread::new(RefCell::new(IncrCompSession::NotInitialized)),
+        incr_comp_session: RwLock::new(IncrCompSession::NotInitialized),
         cgu_reuse_tracker,
         prof,
         perf_stats: PerfStats {