| Message ID | 20250125101854.112261-6-fujita.tomonori@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | rust: Add IO polling | expand |
On Sat, 25 Jan 2025 19:18:50 +0900 FUJITA Tomonori <fujita.tomonori@gmail.com> wrote: > 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. > > sleep functions including fsleep() belongs to TIMERS, not > TIMEKEEPING. They are maintained separately. rust/kernel/time.rs is an > abstraction for TIMEKEEPING. To make Rust abstractions match the C > side, add rust/kernel/time/delay.rs for this wrapper. > > 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] > Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com> Reviewed-by: Gary Guo <gary@garyguo.net> > --- > rust/helpers/helpers.c | 1 + > rust/helpers/time.c | 8 +++++++ > rust/kernel/time.rs | 2 ++ > rust/kernel/time/delay.rs | 49 +++++++++++++++++++++++++++++++++++++++ > 4 files changed, 60 insertions(+) > create mode 100644 rust/helpers/time.c > create mode 100644 rust/kernel/time/delay.rs > > diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c > index dcf827a61b52..d16aeda7a558 100644 > --- a/rust/helpers/helpers.c > +++ b/rust/helpers/helpers.c > @@ -26,6 +26,7 @@ > #include "slab.c" > #include "spinlock.c" > #include "task.c" > +#include "time.c" > #include "uaccess.c" > #include "vmalloc.c" > #include "wait.c" > diff --git a/rust/helpers/time.c b/rust/helpers/time.c > new file mode 100644 > index 000000000000..7ae64ad8141d > --- /dev/null > +++ b/rust/helpers/time.c > @@ -0,0 +1,8 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +#include <linux/delay.h> > + > +void rust_helper_fsleep(unsigned long usecs) > +{ > + fsleep(usecs); > +} > diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs > index d64a05a4f4d1..eeb0f6a7e5d4 100644 > --- a/rust/kernel/time.rs > +++ b/rust/kernel/time.rs > @@ -24,6 +24,8 @@ > //! C header: [`include/linux/jiffies.h`](srctree/include/linux/jiffies.h). > //! C header: [`include/linux/ktime.h`](srctree/include/linux/ktime.h). > > +pub mod delay; > + > /// The number of nanoseconds per microsecond. > pub const NSEC_PER_USEC: i64 = bindings::NSEC_PER_USEC as i64; > > diff --git a/rust/kernel/time/delay.rs b/rust/kernel/time/delay.rs > new file mode 100644 > index 000000000000..02b8731433c7 > --- /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::ffi::c_ulong; > + > +/// 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) > + } > +}
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index dcf827a61b52..d16aeda7a558 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -26,6 +26,7 @@ #include "slab.c" #include "spinlock.c" #include "task.c" +#include "time.c" #include "uaccess.c" #include "vmalloc.c" #include "wait.c" diff --git a/rust/helpers/time.c b/rust/helpers/time.c new file mode 100644 index 000000000000..7ae64ad8141d --- /dev/null +++ b/rust/helpers/time.c @@ -0,0 +1,8 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/delay.h> + +void rust_helper_fsleep(unsigned long usecs) +{ + fsleep(usecs); +} diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs index d64a05a4f4d1..eeb0f6a7e5d4 100644 --- a/rust/kernel/time.rs +++ b/rust/kernel/time.rs @@ -24,6 +24,8 @@ //! C header: [`include/linux/jiffies.h`](srctree/include/linux/jiffies.h). //! C header: [`include/linux/ktime.h`](srctree/include/linux/ktime.h). +pub mod delay; + /// The number of nanoseconds per microsecond. pub const NSEC_PER_USEC: i64 = bindings::NSEC_PER_USEC as i64; diff --git a/rust/kernel/time/delay.rs b/rust/kernel/time/delay.rs new file mode 100644 index 000000000000..02b8731433c7 --- /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::ffi::c_ulong; + +/// 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) + } +}
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. sleep functions including fsleep() belongs to TIMERS, not TIMEKEEPING. They are maintained separately. rust/kernel/time.rs is an abstraction for TIMEKEEPING. To make Rust abstractions match the C side, add rust/kernel/time/delay.rs for this wrapper. 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] Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com> --- rust/helpers/helpers.c | 1 + rust/helpers/time.c | 8 +++++++ rust/kernel/time.rs | 2 ++ rust/kernel/time/delay.rs | 49 +++++++++++++++++++++++++++++++++++++++ 4 files changed, 60 insertions(+) create mode 100644 rust/helpers/time.c create mode 100644 rust/kernel/time/delay.rs