Remove Context::vfork.

Since clone is no longer exists as a syscall, it makes little sense to
manage vfork in the kernel. Implementing vfork in userspace would still
be possible.

src/context/context.rs

@@ -218,8 +218,6 @@ pub struct Context {
     /// Tail buffer to use when system call buffers are not page aligned
     // TODO: Store in user memory?
     pub syscall_tail: Option<RaiiFrame>,
-    /// Context is halting parent
-    pub vfork: bool,
     /// Context is being waited on
     pub waitpid: Arc<WaitMap<WaitpidKey, (ContextId, usize)>>,
     /// Context should handle pending signals
@@ -292,7 +290,6 @@ impl Context {
             syscall: None,
             syscall_head: Some(RaiiFrame::allocate()?),
             syscall_tail: Some(RaiiFrame::allocate()?),
-            vfork: false,
             waitpid: Arc::new(WaitMap::new()),
             pending: VecDeque::new(),
             wake: None,

src/syscall/process.rs

@@ -112,24 +112,18 @@ pub fn exit(status: usize) -> ! {
                 let mut context = context_lock.write();
                 if context.ppid == pid {
                     context.ppid = ppid;
-                    context.vfork = false;
                 }
             }
         }
 
-        let (vfork, children) = {
+        let children = {
             let mut context = context_lock.write();
 
             context = empty(&context_lock, context, false);
 
-            let vfork = context.vfork;
-            context.vfork = false;
-
             context.status = context::Status::Exited(status);
 
-            let children = context.waitpid.receive_all();
-
-            (vfork, children)
+            context.waitpid.receive_all()
         };
 
         {
@@ -137,9 +131,6 @@ pub fn exit(status: usize) -> ! {
             if let Some(parent_lock) = contexts.get(ppid) {
                 let waitpid = {
                     let mut parent = parent_lock.write();
-                    if vfork && ! parent.unblock() {
-                        println!("{}: {} not blocked for exit vfork unblock", pid.into(), ppid.into());
-                    }
                     Arc::clone(&parent.waitpid)
                 };
 
@@ -151,8 +142,6 @@ pub fn exit(status: usize) -> ! {
                     pid: Some(pid),
                     pgid: Some(pgid)
                 }, (pid, status));
-            } else {
-                println!("{}: {} not found for exit vfork unblock", pid.into(), ppid.into());
             }
         }