diff --git a/src/librustc/middle/const_val.rs b/src/librustc/middle/const_val.rs
index 8c3dfd0bce752..19a7576b7ceac 100644
--- a/src/librustc/middle/const_val.rs
+++ b/src/librustc/middle/const_val.rs
@@ -19,7 +19,7 @@ use graphviz::IntoCow;
 use syntax_pos::Span;
 
 use std::borrow::Cow;
-use std::rc::Rc;
+use rustc_data_structures::sync::Lrc;
 
 pub type EvalResult<'tcx> = Result<&'tcx ty::Const<'tcx>, ConstEvalErr<'tcx>>;
 
@@ -52,7 +52,7 @@ impl<'tcx> ConstVal<'tcx> {
 #[derive(Clone, Debug)]
 pub struct ConstEvalErr<'tcx> {
     pub span: Span,
-    pub kind: Rc<ErrKind<'tcx>>,
+    pub kind: Lrc<ErrKind<'tcx>>,
 }
 
 #[derive(Clone, Debug)]
diff --git a/src/librustc/traits/query/dropck_outlives.rs b/src/librustc/traits/query/dropck_outlives.rs
index 1caab6fd89ef9..e16a1082214f7 100644
--- a/src/librustc/traits/query/dropck_outlives.rs
+++ b/src/librustc/traits/query/dropck_outlives.rs
@@ -15,7 +15,7 @@ use std::iter::FromIterator;
 use traits::query::CanonicalTyGoal;
 use ty::{self, Ty, TyCtxt};
 use ty::subst::Kind;
-use std::rc::Rc;
+use rustc_data_structures::sync::Lrc;
 
 impl<'cx, 'gcx, 'tcx> At<'cx, 'gcx, 'tcx> {
     /// Given a type `ty` of some value being dropped, computes a set
@@ -182,13 +182,13 @@ impl_stable_hash_for!(struct DropckOutlivesResult<'tcx> {
 
 impl<'gcx: 'tcx, 'tcx> Canonicalize<'gcx, 'tcx> for QueryResult<'tcx, DropckOutlivesResult<'tcx>> {
     // we ought to intern this, but I'm too lazy just now
-    type Canonicalized = Rc<Canonical<'gcx, QueryResult<'gcx, DropckOutlivesResult<'gcx>>>>;
+    type Canonicalized = Lrc<Canonical<'gcx, QueryResult<'gcx, DropckOutlivesResult<'gcx>>>>;
 
     fn intern(
         _gcx: TyCtxt<'_, 'gcx, 'gcx>,
         value: Canonical<'gcx, Self::Lifted>,
     ) -> Self::Canonicalized {
-        Rc::new(value)
+        Lrc::new(value)
     }
 }
 
diff --git a/src/librustc/traits/query/normalize.rs b/src/librustc/traits/query/normalize.rs
index 70c5cf5f39029..63f50cff4c2ad 100644
--- a/src/librustc/traits/query/normalize.rs
+++ b/src/librustc/traits/query/normalize.rs
@@ -17,7 +17,7 @@ use infer::at::At;
 use infer::canonical::{Canonical, Canonicalize, QueryResult};
 use middle::const_val::ConstVal;
 use mir::interpret::GlobalId;
-use std::rc::Rc;
+use rustc_data_structures::sync::Lrc;
 use traits::{Obligation, ObligationCause, PredicateObligation, Reveal};
 use traits::query::CanonicalProjectionGoal;
 use traits::project::Normalized;
@@ -259,13 +259,13 @@ impl<'gcx: 'tcx, 'tcx> Canonicalize<'gcx, 'tcx> for ty::ParamEnvAnd<'tcx, ty::Pr
 
 impl<'gcx: 'tcx, 'tcx> Canonicalize<'gcx, 'tcx> for QueryResult<'tcx, NormalizationResult<'tcx>> {
     // we ought to intern this, but I'm too lazy just now
-    type Canonicalized = Rc<Canonical<'gcx, QueryResult<'gcx, NormalizationResult<'gcx>>>>;
+    type Canonicalized = Lrc<Canonical<'gcx, QueryResult<'gcx, NormalizationResult<'gcx>>>>;
 
     fn intern(
         _gcx: TyCtxt<'_, 'gcx, 'gcx>,
         value: Canonical<'gcx, Self::Lifted>,
     ) -> Self::Canonicalized {
-        Rc::new(value)
+        Lrc::new(value)
     }
 }
 
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index fd3465f59ebf2..966c96e594fc4 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -161,12 +161,12 @@ impl<'gcx: 'tcx, 'tcx> CtxtInterners<'tcx> {
                  -> Ty<'tcx> {
         let ty = {
             let mut interner = self.type_.borrow_mut();
-            let global_interner = global_interners.map(|interners| {
-                interners.type_.borrow_mut()
-            });
             if let Some(&Interned(ty)) = interner.get(&st) {
                 return ty;
             }
+            let global_interner = global_interners.map(|interners| {
+                interners.type_.borrow_mut()
+            });
             if let Some(ref interner) = global_interner {
                 if let Some(&Interned(ty)) = interner.get(&st) {
                     return ty;
@@ -1010,17 +1010,16 @@ impl<'tcx> InterpretInterner<'tcx> {
     }
 }
 
-impl<'tcx> GlobalCtxt<'tcx> {
+impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// Get the global TyCtxt.
-    pub fn global_tcx<'a>(&'a self) -> TyCtxt<'a, 'tcx, 'tcx> {
+    #[inline]
+    pub fn global_tcx(self) -> TyCtxt<'a, 'gcx, 'gcx> {
         TyCtxt {
-            gcx: self,
-            interners: &self.global_interners
+            gcx: self.gcx,
+            interners: &self.gcx.global_interners,
         }
     }
-}
 
-impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn alloc_generics(self, generics: ty::Generics) -> &'gcx ty::Generics {
         self.global_arenas.generics.alloc(generics)
     }
@@ -1081,12 +1080,13 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         self,
         alloc: interpret::Allocation,
     ) -> &'gcx interpret::Allocation {
-        if let Some(alloc) = self.interpret_interner.inner.borrow().allocs.get(&alloc) {
+        let allocs = &mut self.interpret_interner.inner.borrow_mut().allocs;
+        if let Some(alloc) = allocs.get(&alloc) {
             return alloc;
         }
 
         let interned = self.global_arenas.const_allocs.alloc(alloc);
-        if let Some(prev) = self.interpret_interner.inner.borrow_mut().allocs.replace(interned) {
+        if let Some(prev) = allocs.replace(interned) {
             bug!("Tried to overwrite interned Allocation: {:#?}", prev)
         }
         interned
@@ -1113,24 +1113,26 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     }
 
     pub fn intern_stability(self, stab: attr::Stability) -> &'gcx attr::Stability {
-        if let Some(st) = self.stability_interner.borrow().get(&stab) {
+        let mut stability_interner = self.stability_interner.borrow_mut();
+        if let Some(st) = stability_interner.get(&stab) {
             return st;
         }
 
         let interned = self.global_interners.arena.alloc(stab);
-        if let Some(prev) = self.stability_interner.borrow_mut().replace(interned) {
+        if let Some(prev) = stability_interner.replace(interned) {
             bug!("Tried to overwrite interned Stability: {:?}", prev)
         }
         interned
     }
 
     pub fn intern_layout(self, layout: LayoutDetails) -> &'gcx LayoutDetails {
-        if let Some(layout) = self.layout_interner.borrow().get(&layout) {
+        let mut layout_interner = self.layout_interner.borrow_mut();
+        if let Some(layout) = layout_interner.get(&layout) {
             return layout;
         }
 
         let interned = self.global_arenas.layout.alloc(layout);
-        if let Some(prev) = self.layout_interner.borrow_mut().replace(interned) {
+        if let Some(prev) = layout_interner.replace(interned) {
             bug!("Tried to overwrite interned Layout: {:?}", prev)
         }
         interned
diff --git a/src/librustc/ty/structural_impls.rs b/src/librustc/ty/structural_impls.rs
index c9a69d5405c9a..3fc20508ad7ee 100644
--- a/src/librustc/ty/structural_impls.rs
+++ b/src/librustc/ty/structural_impls.rs
@@ -18,6 +18,7 @@ use ty::{self, Lift, Ty, TyCtxt};
 use ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 use rustc_data_structures::accumulate_vec::AccumulateVec;
 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
+use rustc_data_structures::sync::Lrc;
 use mir::interpret;
 
 use std::rc::Rc;
@@ -465,7 +466,7 @@ impl<'a, 'tcx> Lift<'tcx> for ConstEvalErr<'a> {
         tcx.lift(&*self.kind).map(|kind| {
             ConstEvalErr {
                 span: self.span,
-                kind: Rc::new(kind),
+                kind: Lrc::new(kind),
             }
         })
     }
diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index 81246aea1b56e..bf0b3726bb301 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -76,6 +76,14 @@ pub mod flock;
 pub mod sync;
 pub mod owning_ref;
 
+pub struct OnDrop<F: Fn()>(pub F);
+
+impl<F: Fn()> Drop for OnDrop<F> {
+      fn drop(&mut self) {
+            (self.0)();
+      }
+}
+
 // See comments in src/librustc/lib.rs
 #[doc(hidden)]
 pub fn __noop_fix_for_27438() {}
diff --git a/src/librustc_data_structures/sync.rs b/src/librustc_data_structures/sync.rs
index d7cd459e5771c..184ef1369761c 100644
--- a/src/librustc_data_structures/sync.rs
+++ b/src/librustc_data_structures/sync.rs
@@ -26,11 +26,6 @@
 //!
 //! `MTLock` is a mutex which disappears if cfg!(parallel_queries) is false.
 //!
-//! `rustc_global!` gives us a way to declare variables which are intended to be
-//! global for the current rustc session. This currently maps to thread-locals,
-//! since rustdoc uses the rustc libraries in multiple threads.
-//! These globals should eventually be moved into the `Session` structure.
-//!
 //! `rustc_erase_owner!` erases a OwningRef owner into Erased or Erased + Send + Sync
 //! depending on the value of cfg!(parallel_queries).
 
@@ -228,31 +223,6 @@ pub fn assert_sync<T: ?Sized + Sync>() {}
 pub fn assert_send_val<T: ?Sized + Send>(_t: &T) {}
 pub fn assert_send_sync_val<T: ?Sized + Sync + Send>(_t: &T) {}
 
-#[macro_export]
-#[allow_internal_unstable]
-macro_rules! rustc_global {
-    // empty (base case for the recursion)
-    () => {};
-
-    // process multiple declarations
-    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr; $($rest:tt)*) => (
-        thread_local!($(#[$attr])* $vis static $name: $t = $init);
-        rustc_global!($($rest)*);
-    );
-
-    // handle a single declaration
-    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr) => (
-        thread_local!($(#[$attr])* $vis static $name: $t = $init);
-    );
-}
-
-#[macro_export]
-macro_rules! rustc_access_global {
-    ($name:path, $callback:expr) => {
-        $name.with($callback)
-    }
-}
-
 impl<T: Copy + Debug> Debug for LockCell<T> {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         f.debug_struct("LockCell")
@@ -363,6 +333,13 @@ impl<T> Lock<T> {
     }
 }
 
+impl<T: Default> Default for Lock<T> {
+    #[inline]
+    fn default() -> Self {
+        Lock::new(T::default())
+    }
+}
+
 // FIXME: Probably a bad idea
 impl<T: Clone> Clone for Lock<T> {
     #[inline]
diff --git a/src/librustc_mir/interpret/const_eval.rs b/src/librustc_mir/interpret/const_eval.rs
index 82eb28287b033..50997089a5764 100644
--- a/src/librustc_mir/interpret/const_eval.rs
+++ b/src/librustc_mir/interpret/const_eval.rs
@@ -14,7 +14,7 @@ use super::{Place, EvalContext, StackPopCleanup, ValTy, PlaceExtra, Memory};
 
 use std::fmt;
 use std::error::Error;
-use std::rc::Rc;
+use rustc_data_structures::sync::Lrc;
 
 pub fn mk_borrowck_eval_cx<'a, 'mir, 'tcx>(
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
@@ -477,7 +477,7 @@ pub fn const_eval_provider<'a, 'tcx>(
         // Do match-check before building MIR
         if tcx.check_match(def_id).is_err() {
             return Err(ConstEvalErr {
-                kind: Rc::new(CheckMatchError),
+                kind: Lrc::new(CheckMatchError),
                 span,
             });
         }
@@ -489,7 +489,7 @@ pub fn const_eval_provider<'a, 'tcx>(
         // Do not continue into miri if typeck errors occurred; it will fail horribly
         if tables.tainted_by_errors {
             return Err(ConstEvalErr {
-                kind: Rc::new(TypeckError),
+                kind: Lrc::new(TypeckError),
                 span,
             });
         }
diff --git a/src/librustc_traits/dropck_outlives.rs b/src/librustc_traits/dropck_outlives.rs
index 2a8cfe5cc06b3..1fe2f87128abd 100644
--- a/src/librustc_traits/dropck_outlives.rs
+++ b/src/librustc_traits/dropck_outlives.rs
@@ -16,14 +16,14 @@ use rustc::traits::query::dropck_outlives::{DtorckConstraint, DropckOutlivesResu
 use rustc::ty::{self, ParamEnvAnd, Ty, TyCtxt};
 use rustc::ty::subst::Subst;
 use rustc::util::nodemap::FxHashSet;
-use std::rc::Rc;
+use rustc_data_structures::sync::Lrc;
 use syntax::codemap::{Span, DUMMY_SP};
 use util;
 
 crate fn dropck_outlives<'tcx>(
     tcx: TyCtxt<'_, 'tcx, 'tcx>,
     goal: CanonicalTyGoal<'tcx>,
-) -> Result<Rc<Canonical<'tcx, QueryResult<'tcx, DropckOutlivesResult<'tcx>>>>, NoSolution> {
+) -> Result<Lrc<Canonical<'tcx, QueryResult<'tcx, DropckOutlivesResult<'tcx>>>>, NoSolution> {
     debug!("dropck_outlives(goal={:#?})", goal);
 
     tcx.infer_ctxt().enter(|ref infcx| {
diff --git a/src/librustc_traits/normalize_projection_ty.rs b/src/librustc_traits/normalize_projection_ty.rs
index 55785d9586cc3..62d5ef11551c0 100644
--- a/src/librustc_traits/normalize_projection_ty.rs
+++ b/src/librustc_traits/normalize_projection_ty.rs
@@ -14,7 +14,7 @@ use rustc::traits::{self, FulfillmentContext, Normalized, ObligationCause,
 use rustc::traits::query::{CanonicalProjectionGoal, NoSolution, normalize::NormalizationResult};
 use rustc::ty::{ParamEnvAnd, TyCtxt};
 use rustc::util::common::CellUsizeExt;
-use std::rc::Rc;
+use rustc_data_structures::sync::Lrc;
 use syntax::ast::DUMMY_NODE_ID;
 use syntax_pos::DUMMY_SP;
 use util;
@@ -22,7 +22,7 @@ use util;
 crate fn normalize_projection_ty<'tcx>(
     tcx: TyCtxt<'_, 'tcx, 'tcx>,
     goal: CanonicalProjectionGoal<'tcx>,
-) -> Result<Rc<Canonical<'tcx, QueryResult<'tcx, NormalizationResult<'tcx>>>>, NoSolution> {
+) -> Result<Lrc<Canonical<'tcx, QueryResult<'tcx, NormalizationResult<'tcx>>>>, NoSolution> {
     debug!("normalize_provider(goal={:#?})", goal);
 
     tcx.sess.perf_stats.normalize_projection_ty.increment();
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index bec46ff3d797c..51da9a755ec4f 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -184,8 +184,12 @@ impl SpanData {
     }
 }
 
-// The interner in thread-local, so `Span` shouldn't move between threads.
+// The interner is pointed to by a thread local value which is only set on the main thread
+// with parallelization is disabled. So we don't allow Span to transfer between threads
+// to avoid panics and other errors, even though it would be memory safe to do so.
+#[cfg(not(parallel_queries))]
 impl !Send for Span {}
+#[cfg(not(parallel_queries))]
 impl !Sync for Span {}
 
 impl PartialOrd for Span {
diff --git a/src/libsyntax_pos/symbol.rs b/src/libsyntax_pos/symbol.rs
index e95079f7c88dd..34716e6eeec89 100644
--- a/src/libsyntax_pos/symbol.rs
+++ b/src/libsyntax_pos/symbol.rs
@@ -83,8 +83,12 @@ impl Decodable for Ident {
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct Symbol(u32);
 
-// The interner in thread-local, so `Symbol` shouldn't move between threads.
+// The interner is pointed to by a thread local value which is only set on the main thread
+// with parallelization is disabled. So we don't allow Symbol to transfer between threads
+// to avoid panics and other errors, even though it would be memory safe to do so.
+#[cfg(not(parallel_queries))]
 impl !Send for Symbol { }
+#[cfg(not(parallel_queries))]
 impl !Sync for Symbol { }
 
 impl Symbol {
diff --git a/src/test/run-pass-fulldeps/issue-35829.rs b/src/test/run-pass-fulldeps/issue-35829.rs
index c420243325038..798c214bc4715 100644
--- a/src/test/run-pass-fulldeps/issue-35829.rs
+++ b/src/test/run-pass-fulldeps/issue-35829.rs
@@ -20,8 +20,7 @@ use syntax::ext::expand::ExpansionConfig;
 use syntax::parse::ParseSess;
 use syntax::codemap::{FilePathMapping, dummy_spanned};
 use syntax::print::pprust::expr_to_string;
-use syntax::ast::{Expr, ExprKind, LitKind, StrStyle, RangeLimits};
-use syntax::symbol::Symbol;
+use syntax::ast::{ExprKind, LitKind, RangeLimits};
 use syntax::ptr::P;
 
 use rustc_data_structures::sync::Lrc;