Drop files at the correct time

kernel/src/process/posix_thread/thread_local.rs

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use core::cell::{Cell, RefCell};
+use core::cell::{Cell, Ref, RefCell, RefMut};
 
 use aster_rights::Full;
 use ostd::{mm::Vaddr, sync::RwArc, task::CurrentTask};
@@ -23,7 +23,7 @@ pub struct ThreadLocal {
     robust_list: RefCell<Option<RobustListHead>>,
 
     // Files.
-    file_table: RefCell<RwArc<FileTable>>,
+    file_table: RefCell<Option<RwArc<FileTable>>>,
 
     // Signal.
     /// `ucontext` address for the signal handler.
@@ -38,15 +38,15 @@ impl ThreadLocal {
     pub(super) fn new(
         set_child_tid: Vaddr,
         clear_child_tid: Vaddr,
-        root_vmar: Option<Vmar<Full>>,
+        root_vmar: Vmar<Full>,
         file_table: RwArc<FileTable>,
     ) -> Self {
         Self {
             set_child_tid: Cell::new(set_child_tid),
             clear_child_tid: Cell::new(clear_child_tid),
-            root_vmar: RefCell::new(root_vmar),
+            root_vmar: RefCell::new(Some(root_vmar)),
             robust_list: RefCell::new(None),
-            file_table: RefCell::new(file_table),
+            file_table: RefCell::new(Some(file_table)),
             sig_context: Cell::new(None),
             sig_stack: RefCell::new(None),
         }
@@ -68,8 +68,12 @@ impl ThreadLocal {
         &self.robust_list
     }
 
-    pub fn file_table(&self) -> &RefCell<RwArc<FileTable>> {
-        &self.file_table
+    pub fn borrow_file_table(&self) -> FileTableRef {
+        FileTableRef(self.file_table.borrow())
+    }
+
+    pub fn borrow_file_table_mut(&self) -> FileTableRefMut {
+        FileTableRefMut(self.file_table.borrow_mut())
     }
 
     pub fn sig_context(&self) -> &Cell<Option<Vaddr>> {
@@ -81,6 +85,39 @@ impl ThreadLocal {
     }
 }
 
+/// An immutable, shared reference to the file table in [`ThreadLocal`].
+pub struct FileTableRef<'a>(Ref<'a, Option<RwArc<FileTable>>>);
+
+impl FileTableRef<'_> {
+    /// Unwraps and returns a reference to the file table.
+    ///
+    /// # Panics
+    ///
+    /// This method will panic if the thread has exited and the file table has been dropped.
+    pub fn unwrap(&self) -> &RwArc<FileTable> {
+        self.0.as_ref().unwrap()
+    }
+}
+
+/// A mutable, exclusive reference to the file table in [`ThreadLocal`].
+pub struct FileTableRefMut<'a>(RefMut<'a, Option<RwArc<FileTable>>>);
+
+impl FileTableRefMut<'_> {
+    /// Unwraps and returns a reference to the file table.
+    ///
+    /// # Panics
+    ///
+    /// This method will panic if the thread has exited and the file table has been dropped.
+    pub fn unwrap(&mut self) -> &mut RwArc<FileTable> {
+        self.0.as_mut().unwrap()
+    }
+
+    /// Removes the file table and drops it.
+    pub(super) fn remove(&mut self) {
+        *self.0 = None;
+    }
+}
+
 /// A trait to provide the `as_thread_local` method for tasks.
 pub trait AsThreadLocal {
     /// Returns the associated [`ThreadLocal`].