std: add an RAII unlocker to Mutex.

This automatically unlocks its lock when it goes out of scope, and
provides a safe(ish) method to call .wait.

4 files changed, 15 insertions, 20 deletions

diff --git a/src/libnative/bookkeeping.rs b/src/libnative/bookkeeping.rs
index 868586b3691..e0aaf20e838 100644
--- a/src/libnative/bookkeeping.rs
+++ b/src/libnative/bookkeeping.rs
@@ -29,9 +29,8 @@ pub fn increment() {
 pub fn decrement() {
     unsafe {
         if TASK_COUNT.fetch_sub(1, atomics::SeqCst) == 1 {
-            TASK_LOCK.lock();
-            TASK_LOCK.signal();
-            TASK_LOCK.unlock();
+            let mut guard = TASK_LOCK.lock();
+            guard.signal();
         }
     }
 }
@@ -40,11 +39,12 @@ pub fn decrement() {
 /// the entry points of native programs
 pub fn wait_for_other_tasks() {
     unsafe {
-        TASK_LOCK.lock();
-        while TASK_COUNT.load(atomics::SeqCst) > 0 {
-            TASK_LOCK.wait();
+        {
+            let mut guard = TASK_LOCK.lock();
+            while TASK_COUNT.load(atomics::SeqCst) > 0 {
+                guard.wait();
+            }
         }
-        TASK_LOCK.unlock();
         TASK_LOCK.destroy();
     }
 }
diff --git a/src/libnative/io/net.rs b/src/libnative/io/net.rs
index ec6a5c5cb9b..1de729aee2e 100644
--- a/src/libnative/io/net.rs
+++ b/src/libnative/io/net.rs
@@ -222,7 +222,7 @@ pub fn init() {
         static mut INITIALIZED: bool = false;
         static mut LOCK: Mutex = MUTEX_INIT;
 
-        LOCK.lock();
+        let _guard = LOCK.lock();
         if !INITIALIZED {
             let mut data: WSADATA = mem::init();
             let ret = WSAStartup(0x202,      // version 2.2
@@ -230,7 +230,6 @@ pub fn init() {
             assert_eq!(ret, 0);
             INITIALIZED = true;
         }
-        LOCK.unlock();
     }
 }
 
diff --git a/src/libnative/io/timer_helper.rs b/src/libnative/io/timer_helper.rs
index 2c976e67d25..8ddce2c3990 100644
--- a/src/libnative/io/timer_helper.rs
+++ b/src/libnative/io/timer_helper.rs
@@ -41,7 +41,7 @@ pub fn boot(helper: fn(imp::signal, Port<Req>)) {
     static mut INITIALIZED: bool = false;
 
     unsafe {
-        LOCK.lock();
+        let mut _guard = LOCK.lock();
         if !INITIALIZED {
             let (msgp, msgc) = Chan::new();
             // promote this to a shared channel
@@ -58,7 +58,6 @@ pub fn boot(helper: fn(imp::signal, Port<Req>)) {
             rt::at_exit(proc() { shutdown() });
             INITIALIZED = true;
         }
-        LOCK.unlock();
     }
 }
 
diff --git a/src/libnative/task.rs b/src/libnative/task.rs
index a9c3afbbb16..d940edcadc7 100644
--- a/src/libnative/task.rs
+++ b/src/libnative/task.rs
@@ -191,20 +191,19 @@ impl rt::Runtime for Ops {
             let task = BlockedTask::block(cur_task);
 
             if times == 1 {
-                (*me).lock.lock();
+                let mut guard = (*me).lock.lock();
                 (*me).awoken = false;
                 match f(task) {
                     Ok(()) => {
                         while !(*me).awoken {
-                            (*me).lock.wait();
+                            guard.wait();
                         }
                     }
                     Err(task) => { cast::forget(task.wake()); }
                 }
-                (*me).lock.unlock();
             } else {
                 let mut iter = task.make_selectable(times);
-                (*me).lock.lock();
+                let mut guard = (*me).lock.lock();
                 (*me).awoken = false;
                 let success = iter.all(|task| {
                     match f(task) {
@@ -216,9 +215,8 @@ impl rt::Runtime for Ops {
                     }
                 });
                 while success && !(*me).awoken {
-                    (*me).lock.wait();
+                    guard.wait();
                 }
-                (*me).lock.unlock();
             }
             // re-acquire ownership of the task
             cur_task = cast::transmute::<uint, ~Task>(cur_task_dupe);
@@ -235,10 +233,9 @@ impl rt::Runtime for Ops {
             let me = &mut *self as *mut Ops;
             to_wake.put_runtime(self as ~rt::Runtime);
             cast::forget(to_wake);
-            (*me).lock.lock();
+            let mut guard = (*me).lock.lock();
             (*me).awoken = true;
-            (*me).lock.signal();
-            (*me).lock.unlock();
+            guard.signal();
         }
     }