From: FUJITA Tomonori Date: Tue, 17 Jun 2025 14:41:55 +0000 (+0900) Subject: rust: time: Add wrapper for fsleep() function X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=d4b29ddf82a458935f1bd4909b8a7a13df9d3bdc;p=users%2Fjedix%2Flinux-maple.git rust: time: Add wrapper for fsleep() function 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 Reviewed-by: Alice Ryhl Reviewed-by: Fiona Behrens Tested-by: Daniel Almeida Reviewed-by: Andreas Hindborg Signed-off-by: FUJITA Tomonori Link: https://lore.kernel.org/r/20250617144155.3903431-3-fujita.tomonori@gmail.com Signed-off-by: Andreas Hindborg --- diff --git a/rust/helpers/time.c b/rust/helpers/time.c index 08755db43fc2..a318e9fa4408 100644 --- a/rust/helpers/time.c +++ b/rust/helpers/time.c @@ -1,8 +1,14 @@ // SPDX-License-Identifier: GPL-2.0 +#include #include #include +void rust_helper_fsleep(unsigned long usecs) +{ + fsleep(usecs); +} + ktime_t rust_helper_ktime_get_real(void) { return ktime_get_real(); diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs index 5a9ca0d3b7d4..64c8dcf548d6 100644 --- a/rust/kernel/time.rs +++ b/rust/kernel/time.rs @@ -26,6 +26,7 @@ use core::marker::PhantomData; +pub mod delay; pub mod hrtimer; /// The number of nanoseconds per microsecond. diff --git a/rust/kernel/time/delay.rs b/rust/kernel/time/delay.rs new file mode 100644 index 000000000000..eb8838da62bc --- /dev/null +++ b/rust/kernel/time/delay.rs @@ -0,0 +1,49 @@ +// 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) + } +}