This has one commit from a separate pull request (because these commits depend on that one), but otherwise the extra details can be found in the commit messages. The `rt::thread` module has been generally cleaned up for everyday safe usage (and it's a bug if it's not safe).
* Added doc comments explaining what all public functionality does.
* Added the ability to spawn a detached thread
* Added the ability for the procs to return a value in 'join'
I've noticed I use this pattern quite a bit:
~~~rust
do spawn {
loop {
match port.try_recv() {
Some(x) => ...,
None => ...,
}
}
}
~~~
The `RecvIterator`, returned from a default `recv_iter` method on the `GenericPort` trait, allows you to reduce this down to:
~~~rust
do spawn {
for x in port.recv_iter() {
...
}
}
~~~
As demonstrated in the tests, you can also access the port from within the `for` block for further `recv`ing and `peek`ing with no borrow errors, which is quite nice.
Whenever the runtime is shut down, add a few hooks to clean up some of the
statically initialized data of the runtime. Note that this is an unsafe
operation because there's no guarantee on behalf of the runtime that there's no
other code running which is using the runtime.
This helps turn down the noise a bit in the valgrind output related to
statically initialized mutexes. It doesn't turn the noise down to 0 because
there are still statically initialized mutexes in dynamic_lib and
os::with_env_lock, but I believe that it would be easy enough to add exceptions
for those cases and I don't think that it's the runtime's job to go and clean up
that data.
This moves the locking/waiting methods to returning an RAII struct instead of
relying on closures. Additionally, this changes the methods to all take
'&mut self' to discourage recursive locking. The new method to block is to call
`wait` on the returned RAII structure instead of calling it on the lock itself
(this enforces that the lock is held).
At the same time, this improves the Mutex interface a bit by allowing
destruction of non-initialized members and by allowing construction of an empty
mutex (nothing initialized inside).
This patchset fixes some parts broken on Win64.
This also adds `--disable-pthreads` flags to llvm on mingw-w64 archs (both 32-bit and 64-bit, not mingw) due to bad performance. See #8996 for discussion.
This moves the locking/waiting methods to returning an RAII struct instead of
relying on closures. Additionally, this changes the methods to all take
'&mut self' to discourage recursive locking. The new method to block is to call
`wait` on the returned RAII structure instead of calling it on the lock itself
(this enforces that the lock is held).
At the same time, this improves the Mutex interface a bit by allowing
destruction of non-initialized members and by allowing construction of an empty
mutex (nothing initialized inside).
This is both useful for performance (otherwise logging is unbuffered), but also
useful for correctness. Because when a task is destroyed we can't block the task
waiting for the logger to close, loggers are opened with a 'CloseAsynchronously'
specification. This causes libuv do defer the call to close() until the next
turn of the event loop.
If you spin in a tight loop around printing, you never yield control back to the
libuv event loop, meaning that you simply enqueue a large number of close
requests but nothing is actually closed. This queue ends up never getting
closed, meaning that if you keep trying to create handles one will eventually
fail, which the runtime will attempt to print the failure, causing mass
destruction.
Caching will provide better performance as well as prevent creation of too many
handles.
Closes#10626
The reasons for doing this are:
* The model on which linked failure is based is inherently complex
* The implementation is also very complex, and there are few remaining who
fully understand the implementation
* There are existing race conditions in the core context switching function of
the scheduler, and possibly others.
* It's unclear whether this model of linked failure maps well to a 1:1 threading
model
Linked failure is often a desired aspect of tasks, but we would like to take a
much more conservative approach in re-implementing linked failure if at all.
Closes#8674Closes#8318Closes#8863
This is both useful for performance (otherwise logging is unbuffered), but also
useful for correctness. Because when a task is destroyed we can't block the task
waiting for the logger to close, loggers are opened with a 'CloseAsynchronously'
specification. This causes libuv do defer the call to close() until the next
turn of the event loop.
If you spin in a tight loop around printing, you never yield control back to the
libuv event loop, meaning that you simply enqueue a large number of close
requests but nothing is actually closed. This queue ends up never getting
closed, meaning that if you keep trying to create handles one will eventually
fail, which the runtime will attempt to print the failure, causing mass
destruction.
Caching will provide better performance as well as prevent creation of too many
handles.
Closes#10626
The reasons for doing this are:
* The model on which linked failure is based is inherently complex
* The implementation is also very complex, and there are few remaining who
fully understand the implementation
* There are existing race conditions in the core context switching function of
the scheduler, and possibly others.
* It's unclear whether this model of linked failure maps well to a 1:1 threading
model
Linked failure is often a desired aspect of tasks, but we would like to take a
much more conservative approach in re-implementing linked failure if at all.
Closes#8674Closes#8318Closes#8863
Make TrieMap/TrieSet's find_mut check the key for external nodes.
Without this find_mut sometimes returns a reference to another key when
querying for a non-present key.
This is based off of @blake2-ppc's work on #9429. That PR bitrotted and I haven't been able to contact the original author so I decided to take up the cause.
Overview
======
`Mut` encapsulates a mutable, non-nullable slot. The `Cell` type is currently used to do this, but `Cell` is much more commonly used as a workaround for the inability to move values into non-once functions. `Mut` provides a more robust API.
`Mut` duplicates the semantics of borrowed pointers with enforcement at runtime instead of compile time.
```rust
let x = Mut::new(0);
{
// make some immutable borrows
let p = x.borrow();
let y = *p.get() + 10;
// multiple immutable borrows are allowed simultaneously
let p2 = x.borrow();
// this would throw a runtime failure
// let p_mut = x.borrow_mut();
}
// now we can mutably borrow
let p = x.borrow_mut();
*p.get() = 10;
```
`borrow` returns a `Ref` type and `borrow_mut` returns a `RefMut` type, both of which are simple smart pointer types with a single method, `get`, which returns a reference to the wrapped data.
This also allows `RcMut<T>` to be deleted, as it can be replaced with `Rc<Mut<T>>`.
Changes
======
I've done things a little bit differently than the original proposal.
* I've added `try_borrow` and `try_borrow_mut` methods that return `Option<Ref<T>>` and `Option<RefMut<T>>` respectively instead of failing on a borrow check failure. I'm not totally sure when that'd be useful, but I don't see any reason to not put them in and @cmr requested them.
* `ReadPtr` and `WritePtr` have been renamed to `Ref` and `RefMut` respectively, as `Ref` is to `ref foo` and `RefMut` is to `ref mut foo` as `Mut` is to `mut foo`.
* `get` on `MutRef` now takes `&self` instead of `&mut self` for consistency with `&mut`. As @alexcrichton pointed, out this violates soundness by allowing aliasing `&mut` references.
* `Cell` is being left as is. It solves a different problem than `Mut` is designed to solve.
* There are no longer methods implemented for `Mut<Option<T>>`. Since `Cell` isn't going away, there's less of a need for these, and I didn't feel like they provided a huge benefit, especially as that kind of `impl` is very uncommon in the standard library.
Open Questions
============
* `Cell` should now be used exclusively for movement into closures. Should this be enforced by reducing its API to `new` and `take`? It seems like this use case will be completely going away once the transition to `proc` and co. finishes.
* Should there be `try_map` and `try_map_mut` methods along with `map` and `map_mut`?
