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Update posts to use x86_64 v0.14.2

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Philipp Oppermann
2021-05-17 15:33:35 +02:00
parent b070fa8ee6
commit 5ef39591f6
8 changed files with 76 additions and 76 deletions
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8
blog/content/edition-2/posts/12-async-await/index.md
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@@ -1136,7 +1136,7 @@ To call the `add_scancode` function on keyboard interrupts, we update our `keybo
// in src/interrupts.rs
extern "x86-interrupt" fn keyboard_interrupt_handler(
_stack_frame: &mut InterruptStackFrame
_stack_frame: InterruptStackFrame
) {
use x86_64::instructions::port::Port;
@@ -1744,8 +1744,8 @@ impl Executor {
Since we call `sleep_if_idle` directly after `run_ready_tasks`, which loops until the `task_queue` becomes empty, checking the queue again might seem unnecessary. However, a hardware interrupt might occur directly after `run_ready_tasks` returns, so there might be a new task in the queue at the time the `sleep_if_idle` function is called. Only if the queue is still empty, we put the CPU to sleep by executing the `hlt` instruction through the [`instructions::hlt`] wrapper function provided by the [`x86_64`] crate.
[`instructions::hlt`]: https://docs.rs/x86_64/0.13.2/x86_64/instructions/fn.hlt.html
[`x86_64`]: https://docs.rs/x86_64/0.13.2/x86_64/index.html
[`instructions::hlt`]: https://docs.rs/x86_64/0.14.2/x86_64/instructions/fn.hlt.html
[`x86_64`]: https://docs.rs/x86_64/0.14.2/x86_64/index.html
Unfortunately, there is still a subtle race condition in this implementation. Since interrupts are asynchronous and can happen at any time, it is possible that an interrupt happens right between the `is_empty` check and the call to `hlt`:
@@ -1760,7 +1760,7 @@ In case this interrupt pushes to the `task_queue`, we put the CPU to sleep even
The answer is to disable interrupts on the CPU before the check and atomically enable them again together with the `hlt` instruction. This way, all interrupts that happen in between are delayed after the `hlt` instruction so that no wake-ups are missed. To implement this approach, we can use the [`interrupts::enable_and_hlt`][`enable_and_hlt`] function provided by the [`x86_64`] crate.
[`enable_and_hlt`]: https://docs.rs/x86_64/0.13.2/x86_64/instructions/interrupts/fn.enable_and_hlt.html
[`enable_and_hlt`]: https://docs.rs/x86_64/0.14.2/x86_64/instructions/interrupts/fn.enable_and_hlt.html
The updated implementation of our `sleep_if_idle` function looks like this: