Merge pull request #147 from bastion-rs/thread-yield-overburden-fix

Fix extreme amount of syscalls to give time share to OS

bastion/src/bastion.rs

@@ -8,9 +8,10 @@ use crate::message::{BastionMessage, Message};
 use crate::path::BastionPathElement;
 use crate::supervisor::{Supervisor, SupervisorRef};
 use crate::system::SYSTEM;
+
 use core::future::Future;
+
 use std::fmt::{self, Debug, Formatter};
-use std::thread;
 
 /// A `struct` allowing to access the system's API to initialize it,
 /// start, stop and kill it and to create new supervisors and top-level
@@ -533,6 +534,8 @@ impl Bastion {
             debug!("Bastion: Cancelling system handle.");
             system.cancel();
         }
+
+        SYSTEM.notify_stopped();
     }
 
     /// Blocks the current thread until the system is stopped
@@ -564,16 +567,7 @@ impl Bastion {
     /// [`Bastion::kill()`]: #method.kill
     pub fn block_until_stopped() {
         debug!("Bastion: Blocking until system is stopped.");
-        loop {
-            // FIXME: panics
-            let system = SYSTEM.handle().lock().wait().unwrap();
-            if system.is_none() {
-                debug!("Bastion: Unblocking because system is stopped.");
-                return;
-            }
-
-            thread::yield_now();
-        }
+        SYSTEM.wait_until_stopped();
     }
 }
 

bastion/src/system.rs

@@ -13,19 +13,21 @@ use fxhash::{FxHashMap, FxHashSet};
 use lazy_static::lazy_static;
 use lightproc::prelude::*;
 use qutex::Qutex;
-use std::sync::Arc;
+use std::sync::{Arc, Condvar, Mutex};
 use std::task::Poll;
 
+lazy_static! {
+    pub(crate) static ref SYSTEM: GlobalSystem = System::init();
+}
+
 pub(crate) struct GlobalSystem {
     sender: Sender,
     supervisor: SupervisorRef,
     dead_letters: ChildrenRef,
     path: Arc<BastionPath>,
     handle: Qutex<Option<RecoverableHandle<()>>>,
-}
-
-lazy_static! {
-    pub(crate) static ref SYSTEM: GlobalSystem = System::init();
+    running: Mutex<bool>,
+    stopping_cvar: Condvar,
 }
 
 #[derive(Debug)]
@@ -49,13 +51,17 @@ impl GlobalSystem {
         let handle = Some(handle);
         let handle = Qutex::new(handle);
         let path = Arc::new(BastionPath::root());
+        let running = Mutex::new(true);
+        let stopping_cvar = Condvar::new();
 
         GlobalSystem {
             sender,
             supervisor,
             dead_letters,
             path,
             handle,
+            running,
+            stopping_cvar,
         }
     }
 
@@ -78,6 +84,20 @@ impl GlobalSystem {
     pub(crate) fn path(&self) -> &Arc<BastionPath> {
         &self.path
     }
+
+    pub(crate) fn notify_stopped(&self) {
+        // FIXME: panics
+        *self.running.lock().unwrap() = false;
+        self.stopping_cvar.notify_all();
+    }
+
+    pub(crate) fn wait_until_stopped(&self) {
+        // FIXME: panics
+        let mut running = self.running.lock().unwrap();
+        while *running {
+            running = self.stopping_cvar.wait(running).unwrap();
+        }
+    }
 }
 
 impl System {
@@ -376,6 +396,8 @@ impl System {
                             let mut system = SYSTEM.handle().lock_async().await.unwrap();
                             *system = None;
 
+                            SYSTEM.notify_stopped();
+
                             return;
                         }
                     }
@@ -391,6 +413,8 @@ impl System {
                         let mut system = SYSTEM.handle().lock_async().await.unwrap();
                         *system = None;
 
+                        SYSTEM.notify_stopped();
+
                         return;
                     }
                 }