Revert "Revert "std: Re-enable at_exit()""

This reverts commit aec67c2.

Author: alexcrichton

src/liblog/lib.rs

@@ -184,10 +184,9 @@ use std::old_io::LineBufferedWriter;
 use std::old_io;
 use std::mem;
 use std::env;
-use std::ptr;
 use std::rt;
 use std::slice;
-use std::sync::{Once, ONCE_INIT};
+use std::sync::{Once, ONCE_INIT, StaticMutex, MUTEX_INIT};
 
 use directive::LOG_LEVEL_NAMES;
 
@@ -203,6 +202,8 @@ pub const MAX_LOG_LEVEL: u32 = 255;
 /// The default logging level of a crate if no other is specified.
 const DEFAULT_LOG_LEVEL: u32 = 1;
 
+static LOCK: StaticMutex = MUTEX_INIT;
+
 /// An unsafe constant that is the maximum logging level of any module
 /// specified. This is the first line of defense to determining whether a
 /// logging statement should be run.
@@ -289,9 +290,18 @@ impl Drop for DefaultLogger {
 pub fn log(level: u32, loc: &'static LogLocation, args: fmt::Arguments) {
     // Test the literal string from args against the current filter, if there
     // is one.
-    match unsafe { FILTER.as_ref() } {
-        Some(filter) if !args.to_string().contains(&filter[..]) => return,
-        _ => {}
+    unsafe {
+        let _g = LOCK.lock();
+        match FILTER as uint {
+            0 => {}
+            1 => panic!("cannot log after main thread has exited"),
+            n => {
+                let filter = mem::transmute::<_, &String>(n);
+                if !args.to_string().contains(&filter[..]) {
+                    return
+                }
+            }
+        }
     }
 
     // Completely remove the local logger from TLS in case anyone attempts to
@@ -373,9 +383,15 @@ pub fn mod_enabled(level: u32, module: &str) -> bool {
 
     // This assertion should never get tripped unless we're in an at_exit
     // handler after logging has been torn down and a logging attempt was made.
-    assert!(unsafe { !DIRECTIVES.is_null() });
 
-    enabled(level, module, unsafe { (*DIRECTIVES).iter() })
+    let _g = LOCK.lock();
+    unsafe {
+        assert!(DIRECTIVES as uint != 0);
+        assert!(DIRECTIVES as uint != 1,
+                "cannot log after the main thread has exited");
+
+        enabled(level, module, (*DIRECTIVES).iter())
+    }
 }
 
 fn enabled(level: u32,
@@ -431,14 +447,14 @@ fn init() {
 
         // Schedule the cleanup for the globals for when the runtime exits.
         rt::at_exit(move || {
+            let _g = LOCK.lock();
             assert!(!DIRECTIVES.is_null());
-            let _directives: Box<Vec<directive::LogDirective>> =
-                Box::from_raw(DIRECTIVES);
-            DIRECTIVES = ptr::null_mut();
+            let _directives = Box::from_raw(DIRECTIVES);
+            DIRECTIVES = 1 as *mut _;
 
             if !FILTER.is_null() {
-                let _filter: Box<String> = Box::from_raw(FILTER);
-                FILTER = 0 as *mut _;
+                let _filter = Box::from_raw(FILTER);
+                FILTER = 1 as *mut _;
             }
         });
     }

src/libstd/rt/mod.rs

@@ -147,20 +147,14 @@ fn lang_start(main: *const u8, argc: int, argv: *const *const u8) -> int {
     }
 }
 
-/// Enqueues a procedure to run when the runtime is cleaned up
-///
-/// The procedure passed to this function will be executed as part of the
-/// runtime cleanup phase. For normal rust programs, this means that it will run
-/// after all other threads have exited.
-///
-/// The procedure is *not* executed with a local `Thread` available to it, so
-/// primitives like logging, I/O, channels, spawning, etc, are *not* available.
-/// This is meant for "bare bones" usage to clean up runtime details, this is
-/// not meant as a general-purpose "let's clean everything up" function.
+/// Enqueues a procedure to run when the main thread exits.
 ///
 /// It is forbidden for procedures to register more `at_exit` handlers when they
 /// are running, and doing so will lead to a process abort.
-pub fn at_exit<F:FnOnce()+Send+'static>(f: F) {
+///
+/// Note that other threads may still be running when `at_exit` routines start
+/// running.
+pub fn at_exit<F: FnOnce() + Send + 'static>(f: F) {
     at_exit_imp::push(Thunk::new(f));
 }
 
@@ -176,8 +170,5 @@ pub fn at_exit<F:FnOnce()+Send+'static>(f: F) {
 pub unsafe fn cleanup() {
     args::cleanup();
     sys::stack_overflow::cleanup();
-    // FIXME: (#20012): the resources being cleaned up by at_exit
-    // currently are not prepared for cleanup to happen asynchronously
-    // with detached threads using the resources; for now, we leak.
-    // at_exit_imp::cleanup();
+    at_exit_imp::cleanup();
 }

src/libstd/rt/unwind.rs

@@ -69,7 +69,7 @@ use intrinsics;
 use libc::c_void;
 use mem;
 use sync::atomic::{self, Ordering};
-use sync::{Once, ONCE_INIT};
+use sys_common::mutex::{Mutex, MUTEX_INIT};
 
 use rt::libunwind as uw;
 
@@ -534,11 +534,22 @@ pub fn begin_unwind<M: Any + Send>(msg: M, file_line: &(&'static str, uint)) ->
 /// Doing this split took the LLVM IR line counts of `fn main() { panic!()
 /// }` from ~1900/3700 (-O/no opts) to 180/590.
 #[inline(never)] #[cold] // this is the slow path, please never inline this
-fn begin_unwind_inner(msg: Box<Any + Send>, file_line: &(&'static str, uint)) -> ! {
-    // Make sure the default panic handler is registered before we look at the
-    // callbacks.
-    static INIT: Once = ONCE_INIT;
-    INIT.call_once(|| unsafe { register(panicking::on_panic); });
+fn begin_unwind_inner(msg: Box<Any + Send>,
+                      file_line: &(&'static str, uint)) -> ! {
+    // Make sure the default failure handler is registered before we look at the
+    // callbacks. We also use a raw sys-based mutex here instead of a
+    // `std::sync` one as accessing TLS can cause weird recursive problems (and
+    // we don't need poison checking).
+    unsafe {
+        static LOCK: Mutex = MUTEX_INIT;
+        static mut INIT: bool = false;
+        LOCK.lock();
+        if !INIT {
+            register(panicking::on_panic);
+            INIT = true;
+        }
+        LOCK.unlock();
+    }
 
     // First, invoke call the user-defined callbacks triggered on thread panic.
     //

src/libstd/sys/common/helper_thread.rs

@@ -24,7 +24,6 @@ use prelude::v1::*;
 
 use boxed;
 use cell::UnsafeCell;
-use ptr;
 use rt;
 use sync::{StaticMutex, StaticCondvar};
 use sync::mpsc::{channel, Sender, Receiver};
@@ -97,7 +96,7 @@ impl<M: Send> Helper<M> {
     {
         unsafe {
             let _guard = self.lock.lock().unwrap();
-            if !*self.initialized.get() {
+            if *self.chan.get() as uint == 0 {
                 let (tx, rx) = channel();
                 *self.chan.get() = boxed::into_raw(box tx);
                 let (receive, send) = helper_signal::new();
@@ -113,8 +112,10 @@ impl<M: Send> Helper<M> {
                     self.cond.notify_one()
                 });
 
-                rt::at_exit(move|| { self.shutdown() });
+                rt::at_exit(move || { self.shutdown() });
                 *self.initialized.get() = true;
+            } else if *self.chan.get() as uint == 1 {
+                panic!("cannot continue usage after shutdown");
             }
         }
     }
@@ -129,7 +130,9 @@ impl<M: Send> Helper<M> {
             // Must send and *then* signal to ensure that the child receives the
             // message. Otherwise it could wake up and go to sleep before we
             // send the message.
-            assert!(!self.chan.get().is_null());
+            assert!(*self.chan.get() as uint != 0);
+            assert!(*self.chan.get() as uint != 1,
+                    "cannot continue usage after shutdown");
             (**self.chan.get()).send(msg).unwrap();
             helper_signal::signal(*self.signal.get() as helper_signal::signal);
         }
@@ -142,9 +145,13 @@ impl<M: Send> Helper<M> {
             // returns.
             let mut guard = self.lock.lock().unwrap();
 
+            let ptr = *self.chan.get();
+            if ptr as uint == 1 {
+                panic!("cannot continue usage after shutdown");
+            }
             // Close the channel by destroying it
-            let chan: Box<Sender<M>> = Box::from_raw(*self.chan.get());
-            *self.chan.get() = ptr::null_mut();
+            let chan = Box::from_raw(*self.chan.get());
+            *self.chan.get() = 1 as *mut Sender<M>;
             drop(chan);
             helper_signal::signal(*self.signal.get() as helper_signal::signal);
 

src/libstd/sys/common/thread_local.rs

@@ -61,7 +61,6 @@
 use prelude::v1::*;
 
 use sync::atomic::{self, AtomicUsize, Ordering};
-use sync::{Mutex, Once, ONCE_INIT};
 
 use sys::thread_local as imp;
 
@@ -142,9 +141,6 @@ pub const INIT_INNER: StaticKeyInner = StaticKeyInner {
     key: atomic::ATOMIC_USIZE_INIT,
 };
 
-static INIT_KEYS: Once = ONCE_INIT;
-static mut KEYS: *mut Mutex<Vec<imp::Key>> = 0 as *mut _;
-
 impl StaticKey {
     /// Gets the value associated with this TLS key
     ///

src/libstd/sys/unix/timer.rs

@@ -168,8 +168,15 @@ fn helper(input: libc::c_int, messages: Receiver<Req>, _: ()) {
             1 => {
                 loop {
                     match messages.try_recv() {
+                        // Once we've been disconnected it means the main thread
+                        // is exiting (at_exit has run). We could still have
+                        // active timers for other threads, so we're just going
+                        // to drop them all on the floor. This is all we can
+                        // really do, however, to prevent resource leakage. The
+                        // remaining timers will likely start panicking quickly
+                        // as they attempt to re-use this thread but are
+                        // disallowed to do so.
                         Err(TryRecvError::Disconnected) => {
-                            assert!(active.len() == 0);
                             break 'outer;
                         }
 

src/libstd/sys/windows/thread_local.rs

@@ -138,23 +138,29 @@ unsafe fn init_dtors() {
     rt::at_exit(move|| {
         DTOR_LOCK.lock();
         let dtors = DTORS;
-        DTORS = ptr::null_mut();
+        DTORS = 1 as *mut _;
         Box::from_raw(dtors);
-        assert!(DTORS.is_null()); // can't re-init after destructing
+        assert!(DTORS as uint == 1); // can't re-init after destructing
         DTOR_LOCK.unlock();
     });
 }
 
 unsafe fn register_dtor(key: Key, dtor: Dtor) {
     DTOR_LOCK.lock();
     init_dtors();
+    assert!(DTORS as uint != 0);
+    assert!(DTORS as uint != 1,
+            "cannot create new TLS keys after the main thread has exited");
     (*DTORS).push((key, dtor));
     DTOR_LOCK.unlock();
 }
 
 unsafe fn unregister_dtor(key: Key) -> bool {
     DTOR_LOCK.lock();
     init_dtors();
+    assert!(DTORS as uint != 0);
+    assert!(DTORS as uint != 1,
+            "cannot unregister destructors after the main thread has exited");
     let ret = {
         let dtors = &mut *DTORS;
         let before = dtors.len();

src/libstd/sys/windows/timer.rs

@@ -78,9 +78,10 @@ fn helper(input: libc::HANDLE, messages: Receiver<Req>, _: ()) {
                             None => {}
                         }
                     }
+                    // See the comment in unix::timer for why we don't have any
+                    // asserts here and why we're likely just leaving timers on
+                    // the floor as we exit.
                     Err(TryRecvError::Disconnected) => {
-                        assert_eq!(objs.len(), 1);
-                        assert_eq!(chans.len(), 0);
                         break 'outer;
                     }
                     Err(..) => break

src/test/run-pass/unique-send-2.rs

@@ -25,7 +25,7 @@ pub fn main() {
     let _t = (0..n).map(|i| {
         expected += i;
         let tx = tx.clone();
-        thread::spawn(move|| {
+        thread::scoped(move|| {
             child(&tx, i)
         })
     }).collect::<Vec<_>>();