add thread_name_fn method to runtime::Builder, close #1907.

[biluohc]

Closes #1907.

[biluohc]

loom::sync::Arc(not support ?Sized) looks is different with std::sync::Arc?

But Box<Fn> can not clone, maybe I should use Arc<Box<_>> ?

use std::fmt;
#[cfg(not(loom))]
use std::sync::Arc;
#[cfg(loom)]
use crate::loom::sync::Arc;

error[E0277]: the size for values of type `(dyn std::ops::Fn() -> std::string::String + std::marker::Send + std::marker::Sync + 'static)` cannot be known at compilation time
  --> tokio/src/runtime/builder.rs:58:5
   |
58 |     pub(super) thread_name: ThreadNameFn,
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
   |
   = help: the trait `std::marker::Sized` is not implemented for `(dyn std::ops::Fn() -> std::string::String + std::marker::Send + std::marker::Sync + 'static)`
   = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
   = note: required by `loom::sync::arc::Arc`

error[E0277]: the size for values of type `(dyn std::ops::Fn() -> std::string::String + std::marker::Send + std::marker::Sync + 'static)` cannot be known at compilation time
  --> tokio/src/runtime/blocking/pool.rs:35:5
   |
35 |     thread_name: ThreadNameFn,
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
   |
   = help: the trait `std::marker::Sized` is not implemented for `(dyn std::ops::Fn() -> std::string::String + std::marker::Send + std::marker::Sync + 'static)`
   = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
   = note: required by `loom::sync::arc::Arc`

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.

[onsails]

that's really useful feature for profiling apps using perf record and perf report. Currently there is no ability to focus on a certain thread in perf report.

[hawkw]

Thanks! I think a lot of people are going to find this useful!

I left a few relatively minor suggestions. Overall, the change looks good.

[hawkw]

It's a shame that we have to double-box this to make it work with loom...but, this isn't really a hot path, so it's probably fine for now. It would be good to open an issue against loom about allowing ?Sized Arc type parameters, though...

[hawkw]

Alternatively, I don't think it's super important for the thread name function to participate in loom tests...I think it would be fine to just always use std::sync::Arc here.

[biluohc]

Thanks for your review, I also want to use std::sync::Arc directly.

Do I need to squash the commits to one?

[biluohc]

Code already fomat, but format check failed.

What version of the toolchain is used by ci, I have no problem locally.

 D/e/tokio ╍ (threadname) git log --pretty=one   |head -n 9                                                                                                                                              (%1)
5416579e53fad30635559ced267308e759130f9a ThreadNameFn always use std::sync::Arc
2213fcecf7adbcb28f3ad94c5ee3c032eaad4747 Apply suggestions from code review
ba2c9dc131e05b335772fb666b4b7b7fcbb1138a fix loom test about Arc and features
147760584319d623140d96ddcb107a90351a656d add thread_name_fn method to runtime::Builder, close #1907.
1eb6131321b5bb8e0ccdb7b9433f6f0ef47821f2 codec: Add `Framed::with_capacity` (#2215)
17a6f6fabf4e4d84e5d2807f49f22fc2bd1b359c macros: fix select! documentation formatting (#2283)
ecc23c084a64188e272e2c1e9e370189358a088b chore: prepare v0.2.13 release (#2282)
937ae11f37b0acf6cff9f5808b050f5b8c6ec976 macros: fix unresolved import in pin! (#2281)
f0d18653a6b269d88a61ab37a00abd586b2de173 runtime: add threaded_scheduler to examples (#2277)
 D/e/tokio ╍ (threadname) rustc -V                                                                                                                                                                       (%1)
rustc 1.41.1 (f3e1a954d 2020-02-24)
 D/e/tokio ╍ (threadname)                                                                                                                                                                                (%1)
 D/e/tokio ╍ (threadname) cargo fmt -- --check                                                                                                                                                           (%1)
 D/e/tokio ╍ (threadname) echo $status                                                                                                                                                           (%1) (562ms)
0
 D/e/tokio ╍ (threadname)                                                                                                                                                                                (%1)
 D/e/tokio ╍ (threadname)

[Darksonn]

The cargo fmt command is not quite able to find all of the files, so I recommend you use this command instead:

rustfmt --check --edition 2018 $(find . -name '*.rs' -print)

[Darksonn]

I think this looks good!

[Darksonn]

Sorry. This got a bit lost. Can you update the merge conflict?

[biluohc]

Please deal with it as soon as possible, thanks @Darksonn .