Rollup merge of #84777 - jyn514:rustdoc-parallel, r=Mark-Simulacrum

Apply `--cfg parallel_compiler` when documenting

This also reverts commit 9823c2c working around the bug.

Fixes #82301.

Author: JohnTitor

compiler/rustc_middle/src/ty/query/mod.rs

@@ -232,6 +232,7 @@ macro_rules! define_callbacks {
         }
 
         pub trait QueryEngine<'tcx>: rustc_data_structures::sync::Sync {
+            #[cfg(parallel_compiler)]
             unsafe fn deadlock(&'tcx self, tcx: TyCtxt<'tcx>, registry: &rustc_rayon_core::Registry);
 
             fn encode_query_results(

compiler/rustc_query_impl/src/plumbing.rs

@@ -550,12 +550,10 @@ macro_rules! define_queries_struct {
         }
 
         impl QueryEngine<'tcx> for Queries<'tcx> {
-            unsafe fn deadlock(&'tcx self, _tcx: TyCtxt<'tcx>, _registry: &rustc_rayon_core::Registry) {
-                #[cfg(parallel_compiler)]
-                {
-                    let tcx = QueryCtxt { tcx: _tcx, queries: self };
-                    rustc_query_system::query::deadlock(tcx, _registry)
-                }
+            #[cfg(parallel_compiler)]
+            unsafe fn deadlock(&'tcx self, tcx: TyCtxt<'tcx>, registry: &rustc_rayon_core::Registry) {
+                let tcx = QueryCtxt { tcx, queries: self };
+                rustc_query_system::query::deadlock(tcx, registry)
             }
 
             fn encode_query_results(

src/bootstrap/compile.rs

@@ -648,6 +648,7 @@ pub fn rustc_cargo_env(builder: &Builder<'_>, cargo: &mut Cargo, target: TargetS
     }
     if builder.config.rustc_parallel {
         cargo.rustflag("--cfg=parallel_compiler");
+        cargo.rustdocflag("--cfg=parallel_compiler");
     }
     if builder.config.rust_verify_llvm_ir {
         cargo.env("RUSTC_VERIFY_LLVM_IR", "1");