mirror of https://github.com/torvalds/linux.git
87 lines
3.3 KiB
Rust
87 lines
3.3 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
|
|
|
|
//! Delay and sleep primitives.
|
|
//!
|
|
//! This module contains the kernel APIs related to delay and sleep that
|
|
//! have been ported or wrapped for usage by Rust code in the kernel.
|
|
//!
|
|
//! C header: [`include/linux/delay.h`](srctree/include/linux/delay.h).
|
|
|
|
use super::Delta;
|
|
use crate::prelude::*;
|
|
|
|
/// Sleeps for a given duration at least.
|
|
///
|
|
/// Equivalent to the C side [`fsleep()`], flexible sleep function,
|
|
/// which automatically chooses the best sleep method based on a duration.
|
|
///
|
|
/// `delta` must be within `[0, i32::MAX]` microseconds;
|
|
/// otherwise, it is erroneous behavior. That is, it is considered a bug
|
|
/// to call this function with an out-of-range value, in which case the function
|
|
/// will sleep for at least the maximum value in the range and may warn
|
|
/// in the future.
|
|
///
|
|
/// The behavior above differs from the C side [`fsleep()`] for which out-of-range
|
|
/// values mean "infinite timeout" instead.
|
|
///
|
|
/// This function can only be used in a nonatomic context.
|
|
///
|
|
/// [`fsleep()`]: https://docs.kernel.org/timers/delay_sleep_functions.html#c.fsleep
|
|
pub fn fsleep(delta: Delta) {
|
|
// The maximum value is set to `i32::MAX` microseconds to prevent integer
|
|
// overflow inside fsleep, which could lead to unintentional infinite sleep.
|
|
const MAX_DELTA: Delta = Delta::from_micros(i32::MAX as i64);
|
|
|
|
let delta = if (Delta::ZERO..=MAX_DELTA).contains(&delta) {
|
|
delta
|
|
} else {
|
|
// TODO: Add WARN_ONCE() when it's supported.
|
|
MAX_DELTA
|
|
};
|
|
|
|
// SAFETY: It is always safe to call `fsleep()` with any duration.
|
|
unsafe {
|
|
// Convert the duration to microseconds and round up to preserve
|
|
// the guarantee; `fsleep()` sleeps for at least the provided duration,
|
|
// but that it may sleep for longer under some circumstances.
|
|
bindings::fsleep(delta.as_micros_ceil() as c_ulong)
|
|
}
|
|
}
|
|
|
|
/// Inserts a delay based on microseconds with busy waiting.
|
|
///
|
|
/// Equivalent to the C side [`udelay()`], which delays in microseconds.
|
|
///
|
|
/// `delta` must be within `[0, MAX_UDELAY_MS]` in milliseconds;
|
|
/// otherwise, it is erroneous behavior. That is, it is considered a bug to
|
|
/// call this function with an out-of-range value.
|
|
///
|
|
/// The behavior above differs from the C side [`udelay()`] for which out-of-range
|
|
/// values could lead to an overflow and unexpected behavior.
|
|
///
|
|
/// [`udelay()`]: https://docs.kernel.org/timers/delay_sleep_functions.html#c.udelay
|
|
pub fn udelay(delta: Delta) {
|
|
const MAX_UDELAY_DELTA: Delta = Delta::from_millis(bindings::MAX_UDELAY_MS as i64);
|
|
|
|
debug_assert!(delta.as_nanos() >= 0);
|
|
debug_assert!(delta <= MAX_UDELAY_DELTA);
|
|
|
|
let delta = if (Delta::ZERO..=MAX_UDELAY_DELTA).contains(&delta) {
|
|
delta
|
|
} else {
|
|
MAX_UDELAY_DELTA
|
|
};
|
|
|
|
// SAFETY: It is always safe to call `udelay()` with any duration.
|
|
// Note that the kernel is compiled with `-fno-strict-overflow`
|
|
// so any out-of-range value could lead to unexpected behavior
|
|
// but won't lead to undefined behavior.
|
|
unsafe {
|
|
// Convert the duration to microseconds and round up to preserve
|
|
// the guarantee; `udelay()` inserts a delay for at least
|
|
// the provided duration, but that it may delay for longer
|
|
// under some circumstances.
|
|
bindings::udelay(delta.as_micros_ceil() as c_ulong)
|
|
}
|
|
}
|