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d4b29ddf82
Add a wrapper for fsleep(), flexible sleep functions in include/linux/delay.h which typically deals with hardware delays. The kernel supports several sleep functions to handle various lengths of delay. This adds fsleep(), automatically chooses the best sleep method based on a duration. fsleep() can only be used in a nonatomic context. This requirement is not checked by these abstractions, but it is intended that klint [1] or a similar tool will be used to check it in the future. Link: https://rust-for-linux.com/klint [1] Reviewed-by: Gary Guo <gary@garyguo.net> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Fiona Behrens <me@kloenk.dev> Tested-by: Daniel Almeida <daniel.almeida@collabora.com> Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org> Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com> Link: https://lore.kernel.org/r/20250617144155.3903431-3-fujita.tomonori@gmail.com Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
49 lines
1.9 KiB
Rust
49 lines
1.9 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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//! Delay and sleep primitives.
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//!
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//! This module contains the kernel APIs related to delay and sleep that
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//! have been ported or wrapped for usage by Rust code in the kernel.
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//!
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//! C header: [`include/linux/delay.h`](srctree/include/linux/delay.h).
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use super::Delta;
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use crate::prelude::*;
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/// Sleeps for a given duration at least.
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///
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/// Equivalent to the C side [`fsleep()`], flexible sleep function,
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/// which automatically chooses the best sleep method based on a duration.
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///
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/// `delta` must be within `[0, i32::MAX]` microseconds;
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/// otherwise, it is erroneous behavior. That is, it is considered a bug
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/// to call this function with an out-of-range value, in which case the function
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/// will sleep for at least the maximum value in the range and may warn
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/// in the future.
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///
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/// The behavior above differs from the C side [`fsleep()`] for which out-of-range
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/// values mean "infinite timeout" instead.
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///
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/// This function can only be used in a nonatomic context.
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///
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/// [`fsleep()`]: https://docs.kernel.org/timers/delay_sleep_functions.html#c.fsleep
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pub fn fsleep(delta: Delta) {
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// The maximum value is set to `i32::MAX` microseconds to prevent integer
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// overflow inside fsleep, which could lead to unintentional infinite sleep.
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const MAX_DELTA: Delta = Delta::from_micros(i32::MAX as i64);
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let delta = if (Delta::ZERO..=MAX_DELTA).contains(&delta) {
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delta
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} else {
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// TODO: Add WARN_ONCE() when it's supported.
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MAX_DELTA
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};
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// SAFETY: It is always safe to call `fsleep()` with any duration.
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unsafe {
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// Convert the duration to microseconds and round up to preserve
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// the guarantee; `fsleep()` sleeps for at least the provided duration,
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// but that it may sleep for longer under some circumstances.
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bindings::fsleep(delta.as_micros_ceil() as c_ulong)
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}
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}
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