Auto merge of #140145 - Zoxc:job-server-proxy, r=SparrowLii

Add a jobserver proxy to ensure at least one token is always held

This adds a jobserver proxy to ensure at least one token is always held by `rustc`. Currently with `-Z threads` `rustc` can temporarily give up all its tokens, causing `cargo` to spawn additional `rustc` instances beyond the job limit.

The current behavior causes an issue with `cargo fix` which has a global lock preventing concurrent `rustc` instances, but it also holds a jobserver token, causing a deadlock when `rustc` gives up its token. That is fixed by this PR.

Fixes https://github.com/rust-lang/rust/issues/67385.
Fixes https://github.com/rust-lang/rust/issues/133873.
Fixes https://github.com/rust-lang/rust/issues/140093.

3 files changed, 39 insertions, 14 deletions

diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 708fe23b791..cf494f8d686 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -5,7 +5,7 @@ use std::sync::Arc;
 use rustc_ast::{LitKind, MetaItemKind, token};
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_data_structures::jobserver;
+use rustc_data_structures::jobserver::{self, Proxy};
 use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_errors::registry::Registry;
 use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed};
@@ -40,7 +40,12 @@ pub struct Compiler {
     pub sess: Session,
     pub codegen_backend: Box<dyn CodegenBackend>,
     pub(crate) override_queries: Option<fn(&Session, &mut Providers)>,
+
+    /// A reference to the current `GlobalCtxt` which we pass on to `GlobalCtxt`.
     pub(crate) current_gcx: CurrentGcx,
+
+    /// A jobserver reference which we pass on to `GlobalCtxt`.
+    pub(crate) jobserver_proxy: Arc<Proxy>,
 }
 
 /// Converts strings provided as `--cfg [cfgspec]` into a `Cfg`.
@@ -415,7 +420,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
         config.opts.unstable_opts.threads,
         &config.extra_symbols,
         SourceMapInputs { file_loader, path_mapping, hash_kind, checksum_hash_kind },
-        |current_gcx| {
+        |current_gcx, jobserver_proxy| {
             // The previous `early_dcx` can't be reused here because it doesn't
             // impl `Send`. Creating a new one is fine.
             let early_dcx = EarlyDiagCtxt::new(config.opts.error_format);
@@ -511,6 +516,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
                 codegen_backend,
                 override_queries: config.override_queries,
                 current_gcx,
+                jobserver_proxy,
             };
 
             // There are two paths out of `f`.
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index aad63f4edcf..493b1d5eaa9 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -7,6 +7,7 @@ use std::{env, fs, iter};
 
 use rustc_ast as ast;
 use rustc_codegen_ssa::traits::CodegenBackend;
+use rustc_data_structures::jobserver::Proxy;
 use rustc_data_structures::parallel;
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::sync::{AppendOnlyIndexVec, FreezeLock, WorkerLocal};
@@ -841,12 +842,13 @@ pub fn create_and_enter_global_ctxt<T, F: for<'tcx> FnOnce(TyCtxt<'tcx>) -> T>(
         dyn for<'tcx> FnOnce(
             &'tcx Session,
             CurrentGcx,
+            Arc<Proxy>,
             &'tcx OnceLock<GlobalCtxt<'tcx>>,
             &'tcx WorkerLocal<Arena<'tcx>>,
             &'tcx WorkerLocal<rustc_hir::Arena<'tcx>>,
             F,
         ) -> T,
-    > = Box::new(move |sess, current_gcx, gcx_cell, arena, hir_arena, f| {
+    > = Box::new(move |sess, current_gcx, jobserver_proxy, gcx_cell, arena, hir_arena, f| {
         TyCtxt::create_global_ctxt(
             gcx_cell,
             sess,
@@ -865,6 +867,7 @@ pub fn create_and_enter_global_ctxt<T, F: for<'tcx> FnOnce(TyCtxt<'tcx>) -> T>(
             ),
             providers.hooks,
             current_gcx,
+            jobserver_proxy,
             |tcx| {
                 let feed = tcx.create_crate_num(stable_crate_id).unwrap();
                 assert_eq!(feed.key(), LOCAL_CRATE);
@@ -887,7 +890,15 @@ pub fn create_and_enter_global_ctxt<T, F: for<'tcx> FnOnce(TyCtxt<'tcx>) -> T>(
         )
     });
 
-    inner(&compiler.sess, compiler.current_gcx.clone(), &gcx_cell, &arena, &hir_arena, f)
+    inner(
+        &compiler.sess,
+        compiler.current_gcx.clone(),
+        Arc::clone(&compiler.jobserver_proxy),
+        &gcx_cell,
+        &arena,
+        &hir_arena,
+        f,
+    )
 }
 
 /// Runs all analyses that we guarantee to run, even if errors were reported in earlier analyses.
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 4d346b50c80..087b11fdf9d 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -1,11 +1,12 @@
 use std::env::consts::{DLL_PREFIX, DLL_SUFFIX};
 use std::path::{Path, PathBuf};
-use std::sync::OnceLock;
 use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Arc, OnceLock};
 use std::{env, iter, thread};
 
 use rustc_ast as ast;
 use rustc_codegen_ssa::traits::CodegenBackend;
+use rustc_data_structures::jobserver::Proxy;
 use rustc_data_structures::sync;
 use rustc_metadata::{DylibError, load_symbol_from_dylib};
 use rustc_middle::ty::CurrentGcx;
@@ -124,7 +125,7 @@ fn init_stack_size(early_dcx: &EarlyDiagCtxt) -> usize {
     })
 }
 
-fn run_in_thread_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: Send>(
+fn run_in_thread_with_globals<F: FnOnce(CurrentGcx, Arc<Proxy>) -> R + Send, R: Send>(
     thread_stack_size: usize,
     edition: Edition,
     sm_inputs: SourceMapInputs,
@@ -150,7 +151,7 @@ fn run_in_thread_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: Send>(
                     edition,
                     extra_symbols,
                     Some(sm_inputs),
-                    || f(CurrentGcx::new()),
+                    || f(CurrentGcx::new(), Proxy::new()),
                 )
             })
             .unwrap()
@@ -163,7 +164,10 @@ fn run_in_thread_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: Send>(
     })
 }
 
-pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send, R: Send>(
+pub(crate) fn run_in_thread_pool_with_globals<
+    F: FnOnce(CurrentGcx, Arc<Proxy>) -> R + Send,
+    R: Send,
+>(
     thread_builder_diag: &EarlyDiagCtxt,
     edition: Edition,
     threads: usize,
@@ -173,8 +177,8 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
 ) -> R {
     use std::process;
 
+    use rustc_data_structures::defer;
     use rustc_data_structures::sync::FromDyn;
-    use rustc_data_structures::{defer, jobserver};
     use rustc_middle::ty::tls;
     use rustc_query_impl::QueryCtxt;
     use rustc_query_system::query::{QueryContext, break_query_cycles};
@@ -189,11 +193,11 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
             edition,
             sm_inputs,
             extra_symbols,
-            |current_gcx| {
+            |current_gcx, jobserver_proxy| {
                 // Register the thread for use with the `WorkerLocal` type.
                 registry.register();
 
-                f(current_gcx)
+                f(current_gcx, jobserver_proxy)
             },
         );
     }
@@ -201,10 +205,14 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
     let current_gcx = FromDyn::from(CurrentGcx::new());
     let current_gcx2 = current_gcx.clone();
 
+    let proxy = Proxy::new();
+
+    let proxy_ = Arc::clone(&proxy);
+    let proxy__ = Arc::clone(&proxy);
     let builder = rayon_core::ThreadPoolBuilder::new()
         .thread_name(|_| "rustc".to_string())
-        .acquire_thread_handler(jobserver::acquire_thread)
-        .release_thread_handler(jobserver::release_thread)
+        .acquire_thread_handler(move || proxy_.acquire_thread())
+        .release_thread_handler(move || proxy__.release_thread())
         .num_threads(threads)
         .deadlock_handler(move || {
             // On deadlock, creates a new thread and forwards information in thread
@@ -268,7 +276,7 @@ pub(crate) fn run_in_thread_pool_with_globals<F: FnOnce(CurrentGcx) -> R + Send,
                     },
                     // Run `f` on the first thread in the thread pool.
                     move |pool: &rayon_core::ThreadPool| {
-                        pool.install(|| f(current_gcx.into_inner()))
+                        pool.install(|| f(current_gcx.into_inner(), proxy))
                     },
                 )
                 .unwrap()