The location of a spawned task, as shown in tokio console, is taken from
the location set on the tracing span that instruments the task. For this
location to work, there must be unbroken chain of functions instrumented
with `#[track_caller]`.
For `task::spawn_local`, there was a break in this chain and so the
span contained the location of an internal function in tokio.
This change adds the missing `#[track_caller]` attribute. It has been
tested locally as automated tests would really need `tracing-mock` to be
published so we can use it in the tokio tests.
## Motivation
I found the watch docs as written to be somewhat confusing.
* It wasn't clear to me whether values are marked seen or not at
creation/subscribe time.
* The example also confused me a bit, suggesting a while loop when a
do-while loop is generally more correct.
* I noticed a potential race with `borrow` that is no longer an issue
with `borrow_and_update`.
## Solution
Update the documentation for the watch module to try and make all this
clearer.
This specific issue (data loss because a send got cancelled) has bitten
our team a couple of times over the last few months. We've switched to
recommending this kind of reserve pattern instead.
Currently, Tokio runs cross-compilation checks for the
`mips-unknown-linux-gnu` and `mipsel-unknown-linux-musl` target triples.
However, Rust has recently demoted these targets from Tier 2 support to
Tier 3 (see rust-lang/compiler-team#648). Therefore, MIPS toolchains may
not always be available, even in stable releases. This is currently
[breaking our CI builds][1], as Rust 1.72.0 does not contain a standard
library for `mips-unknown-linux-gnu`.
This branch removes these builds from the cross-compilation check's
build matrix. Tokio may still build successfully for MIPS targets, but
we can't easily guarantee support when the stable Rust release train may
or may not be able to build for MIPS targets.
[1]: https://github.com/tokio-rs/tokio/actions/runs/5970263562/job/16197657405?pr=5947#step:3:80
Tymoteusz Wiśniewski