Remove coordinator and support forking (#53)

Upstream PR: Remove coordinator and support forking

---------

Co-authored-by: mmtkgc-bot <[email protected]>

Author: wks

mmtk/Cargo.lock

@@ -12,7 +12,7 @@ edition = "2021"
 # Metadata for the Ruby repository
 [package.metadata.ci-repos.ruby]
 repo = "mmtk/ruby" # This is used by actions/checkout, so the format is "owner/repo", not URL.
-rev = "6d1596f7a4401d267d2b208c42521edc35020a8e  "
+rev = "e173f879e6e4f1566cca83513e7bfeb4f39331a8"
 
 [lib]
 name = "mmtk_ruby"
@@ -37,7 +37,7 @@ features = ["is_mmtk_object", "object_pinning"]
 
 # Uncomment the following lines to use mmtk-core from the official repository.
 git = "https://github.com/mmtk/mmtk-core.git"
-rev = "dd84218933deab50196fc77828cc1446cb829881"
+rev = "5ab62f96c006475285b00b6d20a8b1bf83b74a4d"
 
 # Uncomment the following line to use mmtk-core from a local repository.
 #path = "../../mmtk-core"

mmtk/Cargo.toml

@@ -1,13 +1,12 @@
 use crate::api::RubyMutator;
 use crate::{upcalls, Ruby};
-use mmtk::scheduler::{GCController, GCWorker};
+use mmtk::scheduler::GCWorker;
 use mmtk::util::{Address, ObjectReference, VMMutatorThread, VMWorkerThread};
 
 // For the C binding
 pub const OBJREF_OFFSET: usize = 8;
 pub const MIN_OBJ_ALIGN: usize = 8; // Even on 32-bit machine.  A Ruby object is at least 40 bytes large.
 
-pub const GC_THREAD_KIND_CONTROLLER: libc::c_int = 0;
 pub const GC_THREAD_KIND_WORKER: libc::c_int = 1;
 
 const HAS_MOVED_GIVTBL: usize = 1 << 63;
@@ -244,10 +243,6 @@ impl GCThreadTLS {
         }
     }
 
-    pub fn for_controller(gc_context: *mut GCController<Ruby>) -> Self {
-        Self::new(GC_THREAD_KIND_CONTROLLER, gc_context as *mut libc::c_void)
-    }
-
     pub fn for_worker(gc_context: *mut GCWorker<Ruby>) -> Self {
         Self::new(GC_THREAD_KIND_WORKER, gc_context as *mut libc::c_void)
     }
@@ -266,7 +261,7 @@ impl GCThreadTLS {
         let result = &mut *ptr;
         debug_assert!({
             let kind = result.kind;
-            kind == GC_THREAD_KIND_CONTROLLER || kind == GC_THREAD_KIND_WORKER
+            kind == GC_THREAD_KIND_WORKER
         });
         result
     }

mmtk/src/abi.rs

@@ -156,6 +156,17 @@ pub extern "C" fn mmtk_initialize_collection(tls: VMThread) {
     memory_manager::initialize_collection(mmtk(), tls)
 }
 
+#[no_mangle]
+pub extern "C" fn mmtk_prepare_to_fork() {
+    mmtk().prepare_to_fork();
+    binding().join_all_gc_threads();
+}
+
+#[no_mangle]
+pub extern "C" fn mmtk_after_fork(tls: VMThread) {
+    mmtk().after_fork(tls);
+}
+
 #[no_mangle]
 pub extern "C" fn mmtk_enable_collection() {
     BINDING_FAST.gc_enabled.store(true, Ordering::Relaxed);

mmtk/src/api.rs

@@ -2,6 +2,7 @@ use std::collections::HashMap;
 use std::ffi::CString;
 use std::sync::atomic::AtomicBool;
 use std::sync::Mutex;
+use std::thread::JoinHandle;
 
 use libc::c_void;
 use mmtk::util::ObjectReference;
@@ -50,6 +51,7 @@ pub struct RubyBinding {
     pub weak_proc: WeakProcessor,
     pub ppp_registry: PPPRegistry,
     pub(crate) moved_givtbl: Mutex<HashMap<ObjectReference, MovedGIVTblEntry>>,
+    pub gc_thread_join_handles: Mutex<Vec<JoinHandle<()>>>,
 }
 
 unsafe impl Sync for RubyBinding {}
@@ -72,6 +74,7 @@ impl RubyBinding {
             weak_proc: WeakProcessor::new(),
             ppp_registry: PPPRegistry::new(),
             moved_givtbl: Default::default(),
+            gc_thread_join_handles: Default::default(),
         }
     }
 
@@ -89,4 +92,20 @@ impl RubyBinding {
         }
         plan_name.as_deref().unwrap().as_ptr()
     }
+
+    pub fn join_all_gc_threads(&self) {
+        let handles = {
+            let mut guard = self.gc_thread_join_handles.lock().unwrap();
+            std::mem::take(&mut *guard)
+        };
+
+        debug!("Joining GC threads...");
+        let total = handles.len();
+        let mut joined = 0;
+        for handle in handles {
+            handle.join().unwrap();
+            joined += 1;
+            debug!("{joined}/{total} GC threads joined.");
+        }
+    }
 }

mmtk/src/binding.rs

@@ -37,53 +37,37 @@ impl Collection<Ruby> for VMCollection {
     }
 
     fn spawn_gc_thread(_tls: VMThread, ctx: GCThreadContext<Ruby>) {
-        match ctx {
-            GCThreadContext::Controller(mut controller) => {
-                thread::Builder::new()
-                    .name("MMTk Controller Thread".to_string())
-                    .spawn(move || {
-                        debug!("Hello! This is MMTk Controller Thread running!");
-                        crate::register_gc_thread(thread::current().id());
-                        let ptr_controller = &mut *controller as *mut GCController<Ruby>;
-                        let gc_thread_tls =
-                            Box::into_raw(Box::new(GCThreadTLS::for_controller(ptr_controller)));
-                        (upcalls().init_gc_worker_thread)(gc_thread_tls);
-                        memory_manager::start_control_collector(
-                            mmtk(),
-                            GCThreadTLS::to_vwt(gc_thread_tls),
-                            &mut controller,
-                        );
+        let join_handle = match ctx {
+            GCThreadContext::Worker(mut worker) => thread::Builder::new()
+                .name("MMTk Worker Thread".to_string())
+                .spawn(move || {
+                    let ordinal = worker.ordinal;
+                    debug!(
+                        "Hello! This is MMTk Worker Thread running! ordinal: {}",
+                        ordinal
+                    );
+                    crate::register_gc_thread(thread::current().id());
+                    let ptr_worker = &mut *worker as *mut GCWorker<Ruby>;
+                    let gc_thread_tls =
+                        Box::into_raw(Box::new(GCThreadTLS::for_worker(ptr_worker)));
+                    (upcalls().init_gc_worker_thread)(gc_thread_tls);
+                    memory_manager::start_worker(
+                        mmtk(),
+                        GCThreadTLS::to_vwt(gc_thread_tls),
+                        worker,
+                    );
+                    debug!(
+                        "An MMTk Worker Thread is quitting. Good bye! ordinal: {}",
+                        ordinal
+                    );
+                    crate::unregister_gc_thread(thread::current().id());
+                })
+                .unwrap(),
+        };
 
-                        // Currently the MMTk controller thread should run forever.
-                        // This is an unlikely event, but we log it anyway.
-                        warn!("The MMTk Controller Thread is quitting!");
-                        crate::unregister_gc_thread(thread::current().id());
-                    })
-                    .unwrap();
-            }
-            GCThreadContext::Worker(mut worker) => {
-                thread::Builder::new()
-                    .name("MMTk Worker Thread".to_string())
-                    .spawn(move || {
-                        debug!("Hello! This is MMTk Worker Thread running!");
-                        crate::register_gc_thread(thread::current().id());
-                        let ptr_worker = &mut *worker as *mut GCWorker<Ruby>;
-                        let gc_thread_tls =
-                            Box::into_raw(Box::new(GCThreadTLS::for_worker(ptr_worker)));
-                        (upcalls().init_gc_worker_thread)(gc_thread_tls);
-                        memory_manager::start_worker(
-                            mmtk(),
-                            GCThreadTLS::to_vwt(gc_thread_tls),
-                            &mut worker,
-                        );
-
-                        // Currently all MMTk worker threads should run forever.
-                        // This is an unlikely event, but we log it anyway.
-                        warn!("An MMTk Worker Thread is quitting!");
-                        crate::unregister_gc_thread(thread::current().id());
-                    })
-                    .unwrap();
-            }
+        {
+            let mut handles = crate::binding().gc_thread_join_handles.lock().unwrap();
+            handles.push(join_handle);
         }
     }