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.

1 files changed, 18 insertions, 10 deletions

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()