forktree worked with depth=3 on k210 platform.

os/src/mm/memory_set.rs

@@ -212,7 +212,7 @@ impl MemorySet {
     pub fn translate(&self, vpn: VirtPageNum) -> Option<PageTableEntry> {
         self.page_table.translate(vpn)
     }
-    pub fn clear(&mut self) {
+    pub fn recycle_data_pages(&mut self) {
         //*self = Self::new_bare();
         self.areas.clear();
     }

os/src/syscall/fs.rs

@@ -1,5 +1,5 @@
 use crate::mm::translated_byte_buffer;
-use crate::task::{current_user_token};
+use crate::task::{current_user_token, suspend_current_and_run_next};
 use crate::sbi::console_getchar;
 
 const FD_STDIN: usize = 0;
@@ -28,7 +28,7 @@ pub fn sys_read(fd: usize, buf: *const u8, len: usize) -> isize {
             loop {
                 c = console_getchar();
                 if c == 0 {
-                    //suspend_current_and_run_next();
+                    suspend_current_and_run_next();
                     continue;
                 } else {
                     break;

os/src/task/mod.rs

@@ -10,6 +10,7 @@ use switch::__switch;
 use task::{TaskControlBlock, TaskStatus};
 use alloc::sync::Arc;
 use manager::fetch_task;
+use lazy_static::*;
 
 pub use context::TaskContext;
 pub use processor::{
@@ -51,22 +52,20 @@ pub fn exit_current_and_run_next(exit_code: i32) {
     inner.task_status = TaskStatus::Zombie;
     // Record exit code
     inner.exit_code = exit_code;
-    // move any child to its parent
-    // TODO: do not move to its parent but under initproc
+    // do not move to its parent but under initproc
 
-    // ++++++ hold parent PCB lock here
+    // ++++++ hold initproc PCB lock here
     {
-        let parent = inner.parent.as_ref().unwrap().upgrade().unwrap();
-        let mut parent_inner = parent.acquire_inner_lock();
+        let mut initproc_inner = INITPROC.acquire_inner_lock();
         for child in inner.children.iter() {
-            parent_inner.children.push(child.clone());
+            initproc_inner.children.push(child.clone());
         }
     }
     // ++++++ release parent PCB lock here
 
     inner.children.clear();
     // deallocate user space
-    inner.memory_set.clear();
+    inner.memory_set.recycle_data_pages();
     drop(inner);
     // **** release current PCB lock
     // drop task manually to maintain rc correctly
@@ -76,7 +75,12 @@ pub fn exit_current_and_run_next(exit_code: i32) {
     schedule(&_unused as *const _);
 }
 
+lazy_static! {
+    pub static ref INITPROC: Arc<TaskControlBlock> = Arc::new(
+        TaskControlBlock::new(get_app_data_by_name("initproc").unwrap())
+    );
+}
+
 pub fn add_initproc() {
-    let data = get_app_data_by_name("initproc").unwrap();
-    add_task(Arc::new(TaskControlBlock::new(data)));
+    add_task(INITPROC.clone());
 }

user/src/bin/forktest2.rs

@@ -30,6 +30,6 @@ pub fn main() -> i32 {
         assert_eq!(xstate, 0);
     }
     assert!(wait(&mut xstate) < 0);
-    println!("r_forktest2 test passed!");
+    println!("forktest2 test passed!");
     0
 }

user/src/bin/forktree.rs

@@ -0,0 +1,37 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user_lib;
+
+use user_lib::{sleep, getpid, fork, exit, yield_};
+
+const DEPTH: usize = 3;
+
+fn fork_child(cur: &str, branch: char) {
+    let mut next = [0u8; DEPTH + 1];
+    let l = cur.len();
+    if l >= DEPTH {
+        return;
+    }
+    &mut next[..l].copy_from_slice(cur.as_bytes());
+    next[l] = branch as u8;
+    if fork() == 0 {
+        fork_tree(core::str::from_utf8(&next[..l + 1]).unwrap());
+        yield_();
+        exit(0);
+    }
+}
+
+fn fork_tree(cur: &str) {
+    println!("pid{}: {}", getpid(), cur);
+    fork_child(cur, '0');
+    fork_child(cur, '1');
+}
+
+#[no_mangle]
+pub fn main() -> i32 {
+    fork_tree("");
+    sleep(3000);
+    0
+}

user/src/bin/initproc.rs

@@ -17,13 +17,17 @@ fn main() -> i32 {
         exec("user_shell\0");
     } else {
         loop {
-            let mut xstatus: i32 = 0;
-            let pid = wait(&mut xstatus);
+            let mut exit_code: i32 = 0;
+            let pid = wait(&mut exit_code);
             if pid == -1 {
                 yield_();
                 continue;
             }
-            println!("[initproc] Release a zombie process!");
+            println!(
+                "[initproc] Released a zombie process, pid={}, exit_code={}",
+                pid,
+                exit_code,
+            );
         }
     }
     0