Ugly impl sys_wait(0)

kernel/src/lib.rs

@@ -10,6 +10,7 @@
 #![feature(global_asm)]
 #![feature(compiler_builtins_lib)]
 #![feature(raw)]
+#![feature(vec_resize_default)]
 #![no_std]
 
 

kernel/src/process/mod.rs

@@ -4,6 +4,8 @@ pub use ucore_process::*;
 use consts::{MAX_CPU_NUM, MAX_PROCESS_NUM};
 use arch::cpu;
 use alloc::{boxed::Box, sync::Arc, vec::Vec};
+use sync::Condvar;
+use core::sync::atomic::*;
 
 mod context;
 
@@ -29,6 +31,55 @@ pub fn init() {
 
 static PROCESSORS: [Processor; MAX_CPU_NUM] = [Processor::new(), Processor::new(), Processor::new(), Processor::new(), Processor::new(), Processor::new(), Processor::new(), Processor::new()];
 
+/// Ugly solution for sys_wait(0) (wait for any child)
+#[derive(Default)]
+pub struct Process {
+    parent: AtomicUsize,
+    children: Mutex<Vec<usize>>,
+    subproc_exit: Condvar,  // Trigger parent's when exit
+}
+
+impl Process {
+    pub fn new_fork(pid: usize, parent: usize) {
+        PROCESS[pid].parent.store(parent, Ordering::Relaxed);
+        PROCESS[pid].subproc_exit._clear();
+        PROCESS[parent].children.lock().push(pid);
+    }
+    pub fn proc_exit(pid: usize) {
+        let parent = PROCESS[pid].parent.load(Ordering::Relaxed);
+        PROCESS[parent].subproc_exit.notify_all();
+    }
+    pub fn wait_child() {
+        Self::current().subproc_exit._wait();
+    }
+    pub fn get_children() -> Vec<usize> {
+        Self::current().children.lock().clone()
+    }
+    pub fn do_wait(pid: usize) {
+        Self::current().children.lock().retain(|&p| p != pid);
+    }
+    fn current() -> &'static Self {
+        &PROCESS[thread::current().id()]
+    }
+}
+
+lazy_static! {
+    pub static ref PROCESS: Vec<Process> = {
+        let mut vec = Vec::new();
+        vec.resize_default(MAX_PROCESS_NUM);
+        vec
+    };
+}
+
+/// Get current thread struct
+pub fn process() -> &'static mut ContextImpl {
+    use core::mem::transmute;
+    let (process, _): (&mut ContextImpl, *const ()) = unsafe {
+        transmute(processor().context())
+    };
+    process
+}
+
 
 // Implement dependencies for std::thread
 

kernel/src/sync/condvar.rs

@@ -33,4 +33,7 @@ impl Condvar {
             t.unpark();
         }
     }
+    pub fn _clear(&self) {
+        self.wait_queue.lock().clear();
+    }
 }

kernel/src/syscall.rs

@@ -58,9 +58,9 @@ fn sys_close(fd: usize) -> i32 {
 
 /// Fork the current process. Return the child's PID.
 fn sys_fork(tf: &TrapFrame) -> i32 {
-    use core::mem::transmute;
-    let (context, _): (&ContextImpl, *const ()) = unsafe { transmute(processor().context()) };
-    let pid = processor().manager().add(context.fork(tf));
+    let mut context = process().fork(tf);
+    let pid = processor().manager().add(context);
+    Process::new_fork(pid, thread::current().id());
     info!("fork: {} -> {}", thread::current().id(), pid);
     pid as i32
 }
@@ -68,21 +68,35 @@ fn sys_fork(tf: &TrapFrame) -> i32 {
 /// Wait the process exit.
 /// Return the PID. Store exit code to `code` if it's not null.
 fn sys_wait(pid: usize, code: *mut i32) -> i32 {
-    assert_ne!(pid, 0, "wait for 0 is not supported yet");
     loop {
-        match processor().manager().get_status(pid) {
-            Some(Status::Exited(exit_code)) => {
-                if !code.is_null() {
-                    unsafe { code.write(exit_code as i32); }
+        let wait_procs = match pid {
+            0 => Process::get_children(),
+            _ => vec![pid],
+        };
+        if wait_procs.is_empty() {
+            return -1;
+        }
+        for pid in wait_procs {
+            match processor().manager().get_status(pid) {
+                Some(Status::Exited(exit_code)) => {
+                    if !code.is_null() {
+                        unsafe { code.write(exit_code as i32); }
+                    }
+                    processor().manager().remove(pid);
+                    Process::do_wait(pid);
+                    info!("wait: {} -> {}", thread::current().id(), pid);
+                    return 0;
                 }
-                processor().manager().remove(pid);
-                return 0;
+                None => return -1,
+                _ => {}
             }
-            None => return -1,
-            _ => {}
         }
-        processor().manager().wait(thread::current().id(), pid);
-        processor().yield_now();
+        if pid == 0 {
+            Process::wait_child();
+        } else {
+            processor().manager().wait(thread::current().id(), pid);
+            processor().yield_now();
+        }
     }
 }
 
@@ -94,6 +108,10 @@ fn sys_yield() -> i32 {
 /// Kill the process
 fn sys_kill(pid: usize) -> i32 {
     processor().manager().exit(pid, 0x100);
+    Process::proc_exit(pid);
+    if pid == thread::current().id() {
+        processor().yield_now();
+    }
     0
 }
 
@@ -106,6 +124,7 @@ fn sys_getpid() -> i32 {
 fn sys_exit(exit_code: usize) -> i32 {
     let pid = thread::current().id();
     processor().manager().exit(pid, exit_code);
+    Process::proc_exit(pid);
     processor().yield_now();
     unreachable!();
 }