94b3953853
Fix `thread::sleep` Duration-handling for ESP-IDF Addresses the ESP-IDF specific aspect of https://github.com/rust-lang/rust/issues/129212 #### A short summary of the problems addressed by this PR: ================================================ 1. **Problem 1** - the current implementation of `std:🧵:sleep` does not properly round up the passed `Duration` As per the documentation of `std:🧵:sleep`, the implementation should sleep _at least_ for the provided duration, but not less. Since the minimum supported resolution of the `usleep` syscall which is used with ESP-IDF is one microsecond, this means that we need to round-up any sub-microsecond nanos to one microsecond. Moreover, in the edge case where the user had passed a duration of < 1000 nanos (i.e. less than one microsecond), the current implementation will _not_ sleep _at all_. This is addressed by this PR. 2. **Problem 2** - the implementation of `usleep` on the ESP-IDF can overflow if the passed number of microseconds is >= `u32::MAX - 1_000_000` This is also addressed by this PR. Extra details for Problem 2: `u32::MAX - 1_000_000` is chosen to accommodate for the longest possible systick on the ESP IDF which is 1000ms. The systick duration is selected when compiling the ESP IDF FreeRTOS task scheduler itself, so we can't know it from within `STD`. The default systick duration is 10ms, and might be lowered down to 1ms. (Making it longer I have never seen, but in theory it can go up to a 1000ms max, even if obviously a one second systick is unrealistic - but we are paranoid in the PR.) While the overflow is reported upstream in the ESP IDF repo[^1], I still believe we should workaround it in the Rust wrappers as well, because it might take time until it is fixed, and they might not fix it for all released ESP IDF versions. For big durations, rather than calling `usleep` repeatedly on the ESP-IDF in chunks of `u32::MAX - 1_000_000`us, it might make sense to call instead with 1_000_000us (one second) as this is the max period that seems to be agreed upon as a safe max period in the `usleep` POSIX spec. On the other hand, that might introduce less precision (as we need to call more times `usleep` in a loop) and, we would be fighting a theoretical problem only, as I have big doubts the ESP IDF will stop supporting durations higher than 1_000_000us - ever - because of backwards compatibility with code which already calls `usleep` on the ESP IDF with bigger durations. [^1]: https://github.com/espressif/esp-idf/issues/14390 |
||
|---|---|---|
| .github | ||
| compiler | ||
| library | ||
| LICENSES | ||
| src | ||
| tests | ||
| .clang-format | ||
| .editorconfig | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitignore | ||
| .gitmodules | ||
| .ignore | ||
| .mailmap | ||
| Cargo.lock | ||
| Cargo.toml | ||
| CODE_OF_CONDUCT.md | ||
| config.example.toml | ||
| configure | ||
| CONTRIBUTING.md | ||
| COPYRIGHT | ||
| INSTALL.md | ||
| LICENSE-APACHE | ||
| LICENSE-MIT | ||
| README.md | ||
| RELEASES.md | ||
| REUSE.toml | ||
| rust-bors.toml | ||
| rustfmt.toml | ||
| triagebot.toml | ||
| x | ||
| x.ps1 | ||
| x.py | ||
This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.
Why Rust?
-
Performance: Fast and memory-efficient, suitable for critical services, embedded devices, and easily integrate with other languages.
-
Reliability: Our rich type system and ownership model ensure memory and thread safety, reducing bugs at compile-time.
-
Productivity: Comprehensive documentation, a compiler committed to providing great diagnostics, and advanced tooling including package manager and build tool (Cargo), auto-formatter (rustfmt), linter (Clippy) and editor support (rust-analyzer).
Quick Start
Read "Installation" from The Book.
Installing from Source
If you really want to install from source (though this is not recommended), see INSTALL.md.
Getting Help
See https://www.rust-lang.org/community for a list of chat platforms and forums.
Contributing
See CONTRIBUTING.md.
License
Rust is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), with portions covered by various BSD-like licenses.
See LICENSE-APACHE, LICENSE-MIT, and COPYRIGHT for details.
Trademark
The Rust Foundation owns and protects the Rust and Cargo trademarks and logos (the "Rust Trademarks").
If you want to use these names or brands, please read the media guide.
Third-party logos may be subject to third-party copyrights and trademarks. See Licenses for details.