Adds a builder API for spawning tasks. Initially, this enables the caller to name the spawned
task in order to provide better visibility into all tasks in the system.
This patch documents cancellation safety. It also moves the "Avoid racy if preconditions"
section in the select! documentation since otherwise the first code block on the page
shows how not to use it, which seems counterintuitive.
Tokio 1.7.0 introduced a change intended to eagerly shutdown newly
spawned tasks if the runtime is in the process of shutting down.
However, it introduced a bug where already spawned tasks could be
shutdown too early, resulting in the potential introduction of deadlocks
if tasks acquired mutexes in drop handlers.
Fixes#3869
This builds on https://github.com/tokio-rs/mio/pull/1351 and introduces the
tokio::net::windows::named_pipe module which provides low level types for
building and communicating asynchronously over windows named pipes.
Named pipes require the `net` feature flag to be enabled on Windows.
Co-authored-by: Alice Ryhl <alice@ryhl.io>
Instead of using sleep in time::advance, this fixes the root of the issue. When futures passed
to `Runtime::block_on` are woken, it bypassed all the machinery around advancing time. By
intercepting wakes in the time driver, we know when the block_on task is woken and skip
advancing time in that case.
Fixes#3837
## Motivation
In support of tokio-rs/console#37, we want to understand when a specific task's waker has been interacted with, such as when it is awoken, or if it's forgotten (not cloned), etc.
## Solution
When the tracing feature is enabled, a super trait of Future (InstrumentedFuture) is implemented for Instrumented<F> that allows grabbing the task's ID (well, its span ID), and stores that in the raw task trailer. The waker vtable then emits events and includes that ID.
This commit fixed issue #3787 by removing [doc(inline)] from
macro `cfg_macros` and added proper #[doc(inline)] attributes
to `pub use` items inside `cfg_macros` calls.
It's probably not `cfg_macros`s responsibility to inlining public
macros, though it's conveninent to do so. Notice that in lib.rs:
cfg_macros! {
/// Implementation detail of the `select!` macro. This macro is **not**
/// intended to be used as part of the public API and is permitted to
/// change.
#[doc(hidden)]
pub use tokio_macros::select_priv_declare_output_enum;
...
}
`#[doc(hidden)]` and `#[doc(inline)]` are conflict with each other
in the sense of correctness.
Fixes: #3787
