Remove GcxPtr

compiler/rustc_middle/src/ty/context.rs

@@ -40,9 +40,9 @@ use rustc_data_structures::profiling::SelfProfilerRef;
 use rustc_data_structures::sharded::{IntoPointer, ShardedHashMap};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
-#[cfg(parallel_compiler)]
-use rustc_data_structures::sync::DynSend;
-use rustc_data_structures::sync::{self, FreezeReadGuard, Lock, Lrc, RwLock, WorkerLocal};
+use rustc_data_structures::sync::{
+    DynSend, DynSync, FreezeReadGuard, Lock, Lrc, RwLock, WorkerLocal,
+};
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::{
     DecorateLint, DiagnosticBuilder, DiagnosticMessage, ErrorGuaranteed, MultiSpan,
@@ -542,7 +542,7 @@ pub struct GlobalCtxt<'tcx> {
     ///
     /// FIXME(Centril): consider `dyn LintStoreMarker` once
     /// we can upcast to `Any` for some additional type safety.
-    pub lint_store: Lrc<dyn Any + sync::DynSync + sync::DynSend>,
+    pub lint_store: Lrc<dyn Any + DynSync + DynSend>,
 
     pub dep_graph: DepGraph,
 
@@ -601,32 +601,22 @@ impl<'tcx> GlobalCtxt<'tcx> {
     {
         let icx = tls::ImplicitCtxt::new(self);
 
-        let gcx_ptr =
-            GcxPtr { value: Lrc::new(RwLock::new(Some(icx.tcx.gcx as *const _ as *const ()))) };
-
-        // Reset `gcx_ptr` to `None` when we exit.
-        let gcx_ptr_ = gcx_ptr.clone();
+        // Reset `current_gcx` to `None` when we exit.
         let _on_drop = defer(move || {
-            *gcx_ptr_.value.write() = None;
+            *self.current_gcx.value.write() = None;
         });
 
         // Set this `GlobalCtxt` as the current one.
-        *self.current_gcx.value.lock() = Some(gcx_ptr);
+        {
+            let mut guard = self.current_gcx.value.write();
+            assert!(guard.is_none(), "no `GlobalCtxt` is currently set");
+            *guard = Some(self as *const _ as *const ());
+        }
 
         tls::enter_context(&icx, || f(icx.tcx))
     }
 }
 
-/// This stores a pointer to a `GlobalCtxt`. When the `GlobalCtxt` is no longer available the lock
-/// will be set to `None`.
-#[derive(Clone)]
-struct GcxPtr {
-    value: Lrc<RwLock<Option<*const ()>>>,
-}
-
-#[cfg(parallel_compiler)]
-unsafe impl DynSend for GcxPtr {}
-
 /// This is used to get a reference to a `GlobalCtxt` if one is available.
 ///
 /// This is needed to allow the deadlock handler access to `GlobalCtxt` to look for query cycles.
@@ -635,21 +625,27 @@ unsafe impl DynSend for GcxPtr {}
 /// the deadlock handler is not called inside such a job.
 #[derive(Clone)]
 pub struct CurrentGcx {
-    value: Lrc<Lock<Option<GcxPtr>>>,
+    /// This stores a pointer to a `GlobalCtxt`. This is set to `Some` inside `GlobalCtxt::enter`
+    /// and reset to `None` when that function returns or unwinds.
+    value: Lrc<RwLock<Option<*const ()>>>,
 }
 
+#[cfg(parallel_compiler)]
+unsafe impl DynSend for CurrentGcx {}
+#[cfg(parallel_compiler)]
+unsafe impl DynSync for CurrentGcx {}
+
 impl CurrentGcx {
     pub fn new() -> Self {
-        Self { value: Lrc::new(Lock::new(None)) }
+        Self { value: Lrc::new(RwLock::new(None)) }
     }
 
     pub fn access<R>(&self, f: impl for<'tcx> FnOnce(&'tcx GlobalCtxt<'tcx>) -> R) -> R {
-        let gcx_ptr = self.value.lock().clone().unwrap();
-        let read_guard = gcx_ptr.value.read();
+        let read_guard = self.value.read();
         let gcx: *const GlobalCtxt<'_> = read_guard.unwrap() as *const _;
-        // SAFETY: We hold the read lock for `GcxPtr`. That prevents `GlobalCtxt::enter` from
-        // returning as it would first acquire the write lock. This ensures the `GlobalCtxt` is
-        // live during `f`.
+        // SAFETY: We hold the read lock for the `GlobalCtxt` pointer. That prevents
+        // `GlobalCtxt::enter` from returning as it would first acquire the write lock.
+        // This ensures the `GlobalCtxt` is live during `f`.
         f(unsafe { &*gcx })
     }
 }
@@ -755,7 +751,7 @@ impl<'tcx> TyCtxt<'tcx> {
         s: &'tcx Session,
         crate_types: Vec<CrateType>,
         stable_crate_id: StableCrateId,
-        lint_store: Lrc<dyn Any + sync::DynSend + sync::DynSync>,
+        lint_store: Lrc<dyn Any + DynSend + DynSync>,
         arena: &'tcx WorkerLocal<Arena<'tcx>>,
         hir_arena: &'tcx WorkerLocal<hir::Arena<'tcx>>,
         untracked: Untracked,