Fix sigchld test.

src/scheme/pipe.rs

@@ -213,6 +213,11 @@ impl KernelScheme for PipeScheme {
         loop {
             let mut vec = pipe.queue.lock();
 
+            if !pipe.reader_is_alive.load(Ordering::Relaxed) {
+                return Err(Error::new(EPIPE));
+            }
+
+
             let bytes_left = MAX_QUEUE_SIZE.saturating_sub(vec.len());
             let bytes_to_write = core::cmp::min(bytes_left, user_buf.len());
             let src_buf = user_buf
@@ -244,9 +249,7 @@ impl KernelScheme for PipeScheme {
                 return Ok(0);
             }
 
-            if !pipe.reader_is_alive.load(Ordering::SeqCst) {
-                return Err(Error::new(EPIPE));
-            } else if fcntl_flags & O_NONBLOCK as u32 != 0 {
+            if fcntl_flags & O_NONBLOCK as u32 != 0 {
                 return Err(Error::new(EAGAIN));
             } else if !pipe.write_condition.wait(vec, "PipeWrite::write") {
                 return Err(Error::new(EINTR));

src/syscall/process.rs

@@ -91,7 +91,9 @@ pub fn exit(status: usize) -> ! {
             let process = current_process.read();
             (process.pgid, process.ppid)
         };
-        let _ = kill(ppid, SIGCHLD);
+        if let Some(parent) = process::PROCESSES.read().get(&ppid).map(Arc::clone) {
+            let _ = send_signal(KillTarget::Process(parent), SIGCHLD, true, &mut false);
+        }
 
         // Transfer child processes to parent (TODO: to init)
         {
@@ -365,19 +367,21 @@ pub fn send_signal(
             send_signal(KillTarget::Process(parent), SIGCHLD, true, killed_self)?;
         }
         Sent::SucceededSigcont { ppid, pgid } => {
-            process::PROCESSES
+            let parent = process::PROCESSES
                 .read()
                 .get(&ppid)
-                .ok_or(Error::new(ESRCH))?
-                .read()
-                .waitpid
-                .send(
-                    WaitpidKey {
-                        pid: Some(proc_info.pid),
-                        pgid: Some(pgid),
-                    },
-                    (proc_info.pid, 0xffff),
-                );
+                .map(Arc::clone)
+                .ok_or(Error::new(ESRCH))?;
+            let waitpid = Arc::clone(&parent.read().waitpid);
+            waitpid.send(
+                WaitpidKey {
+                    pid: Some(proc_info.pid),
+                    pgid: Some(pgid),
+                },
+                (proc_info.pid, 0xffff),
+            );
+            // POSIX XSI allows but does not require SIGCONT to send signals to the parent.
+            //send_signal(KillTarget::Process(parent), SIGCHLD, true, killed_self)?;
         }
     }
 

src/syscall/time.rs

@@ -74,5 +74,7 @@ pub fn nanosleep(req_buf: UserSliceRo, rem_buf_opt: Option<UserSliceWo>) -> Resu
 
 pub fn sched_yield() -> Result<()> {
     context::switch();
+    // TODO: Do this check in userspace
+    context::signal::signal_handler();
     Ok(())
 }