SIGCHLD handling

src/main.rs

@@ -95,15 +95,10 @@ fn main() {
                         } else {
                             child.terminate();
                         }
-
-                        child.wait();
                     },
-                    Signal::Stop => {
-                        child.pause();
-                    },
-                    Signal::Continue => {
-                        child.resume();
-                    }
+                    Signal::Stop => child.pause(),
+                    Signal::Continue => child.resume(),
+                    Signal::ChildExit => child.reap(),
                 }
             }
         }
@@ -153,6 +148,7 @@ fn main() {
     }
 
     loop {
+        debug!("Waiting for filesystem activity");
         let paths = wait(&rx, &filter);
         if let Some(path) = paths.get(0) {
             debug!("Path updated: {:?}", path);
@@ -182,6 +178,7 @@ fn main() {
             cli::clear_screen();
         }
 
+        debug!("Launching child process");
         {
             let mut guard = child_process.write().unwrap();
             *guard = Some(process::spawn(&args.cmd, paths));

src/process.rs

@@ -12,9 +12,12 @@ mod imp {
     use std::io::Result;
     use std::path::PathBuf;
     use std::process::Command;
+    use std::sync::*;
 
     pub struct Process {
         pgid: pid_t,
+        lock: Mutex<bool>,
+        cvar: Condvar,
     }
 
     impl Process {
@@ -55,7 +58,11 @@ mod imp {
                     }
                     let _ = close(w);
 
-                    Ok(Process { pgid: child })
+                    Ok(Process {
+                        pgid: child,
+                        lock: Mutex::new(false),
+                        cvar: Condvar::new(),
+                    })
                 }
                 Ok(ForkResult::Child) => {
                     let _ = setpgid(0, 0);
@@ -85,6 +92,25 @@ mod imp {
             self.signal(SIGTSTP);
         }
 
+        pub fn reap(&self) {
+            use nix::sys::wait::*;
+
+            let mut finished = true;
+            loop {
+                match waitpid(-self.pgid, Some(WNOHANG)) {
+                    Ok(WaitStatus::Exited(_, _)) => finished = finished && true,
+                    Ok(WaitStatus::Signaled(_, _, _)) => finished = finished && true,
+                    Ok(_) => finished = false,
+                    Err(_) => break
+                }
+            }
+
+            if finished {
+                let mut done = self.lock.lock().unwrap();
+                *done = true;
+                self.cvar.notify_one();
+            }
+        }
 
         pub fn resume(&self) {
             self.signal(SIGCONT);
@@ -106,9 +132,10 @@ mod imp {
         }
 
         pub fn wait(&self) {
-            use nix::sys::wait::waitpid;
-
-            while let Ok(_) = waitpid(-self.pgid, None) {}
+            let mut done = self.lock.lock().unwrap();
+            while !*done {
+                done = self.cvar.wait(done).unwrap();
+            }
         }
     }
 }
@@ -181,6 +208,9 @@ mod imp {
         pub fn pause(&self) {
         }
 
+        pub fn reap(&self) {
+        }
+
         pub fn resume(&self) {
         }
 
@@ -190,7 +220,6 @@ mod imp {
             }
         }
 
-
         pub fn wait(&self) {
             unsafe {
                 let _ = WaitForSingleObject(self.job, INFINITE);

src/signal.rs

@@ -7,7 +7,8 @@ lazy_static! {
 pub enum Signal {
     Terminate,
     Stop,
-    Continue
+    Continue,
+    ChildExit
 }
 
 #[cfg(unix)]
@@ -15,6 +16,7 @@ pub fn install_handler<F>(handler: F)
     where F: Fn(self::Signal) + 'static + Send + Sync
 {
     use std::thread;
+    use libc::c_int;
     use nix::sys::signal::*;
 
     // Mask all signals interesting to us. The mask propagates
@@ -24,20 +26,32 @@ pub fn install_handler<F>(handler: F)
     mask.add(SIGINT);
     mask.add(SIGTSTP);
     mask.add(SIGCONT);
+    mask.add(SIGCHLD);
     mask.thread_set_mask().expect("unable to set signal mask");
 
     set_handler(handler);
 
+    // Indicate interest in SIGCHLD by setting a dummy handler
+    pub extern "C" fn sigchld_handler(_: c_int) {
+    }
+
+    unsafe {
+        let _ = sigaction(SIGCHLD, &SigAction::new(
+                SigHandler::Handler(sigchld_handler), SaFlags::empty(), SigSet::empty()));
+    }
+
     // Spawn a thread to catch these signals
     thread::spawn(move || {
         loop {
             let raw_signal = mask.wait().expect("unable to sigwait");
+            debug!("Received {:?}", raw_signal);
 
             let sig = match raw_signal {
                 SIGTERM => self::Signal::Terminate,
                 SIGINT  => self::Signal::Terminate,
                 SIGTSTP => self::Signal::Stop,
                 SIGCONT => self::Signal::Continue,
+                SIGCHLD => self::Signal::ChildExit,
                 _       => unreachable!()
             };
 
@@ -45,10 +59,12 @@ pub fn install_handler<F>(handler: F)
             invoke(sig);
 
             // Restore default behavior for received signal and unmask it
-            let default_action = SigAction::new(SigHandler::SigDfl, SaFlags::empty(), SigSet::empty());
+            if raw_signal != SIGCHLD {
+                let default_action = SigAction::new(SigHandler::SigDfl, SaFlags::empty(), SigSet::empty());
 
-            unsafe {
-                let _ = sigaction(raw_signal, &default_action);
+                unsafe {
+                    let _ = sigaction(raw_signal, &default_action);
+                }
             }
 
             let mut new_mask = SigSet::empty();