| Message ID | 20250220070611.214262-8-fujita.tomonori@gmail.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | rust: Add IO polling | expand |
FUJITA Tomonori <fujita.tomonori@gmail.com> writes: > Add read_poll_timeout functions which poll periodically until a > condition is met or a timeout is reached. > > The C's read_poll_timeout (include/linux/iopoll.h) is a complicated > macro and a simple wrapper for Rust doesn't work. So this implements > the same functionality in Rust. > > The C version uses usleep_range() while the Rust version uses > fsleep(), which uses the best sleep method so it works with spans that > usleep_range() doesn't work nicely with. > > The sleep_before_read argument isn't supported since there is no user > for now. It's rarely used in the C version. > > read_poll_timeout() 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] > Tested-by: Daniel Almeida <daniel.almeida@collabora.com> > Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com> Reviewed-by: Fiona Behrens <me@kloenk.dev> > --- > rust/helpers/helpers.c | 1 + > rust/helpers/kernel.c | 18 +++++++ > rust/kernel/cpu.rs | 13 +++++ > rust/kernel/error.rs | 1 + > rust/kernel/io.rs | 2 + > rust/kernel/io/poll.rs | 120 +++++++++++++++++++++++++++++++++++++++++ > rust/kernel/lib.rs | 1 + > 7 files changed, 156 insertions(+) > create mode 100644 rust/helpers/kernel.c > create mode 100644 rust/kernel/cpu.rs > create mode 100644 rust/kernel/io/poll.rs > > diff --git a/rust/kernel/io/poll.rs b/rust/kernel/io/poll.rs > new file mode 100644 > index 000000000000..5977b2082cc6 > --- /dev/null > +++ b/rust/kernel/io/poll.rs > @@ -0,0 +1,120 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +//! IO polling. > +//! > +//! C header: [`include/linux/iopoll.h`](srctree/include/linux/iopoll.h). > + > +use crate::{ > + cpu::cpu_relax, > + error::{code::*, Result}, > + time::{delay::fsleep, Delta, Instant}, > +}; > + > +/// Polls periodically until a condition is met or a timeout is reached. > +/// > +/// The function repeatedly executes the given operation `op` closure and > +/// checks its result using the condition closure `cond`. > +/// If `cond` returns `true`, the function returns successfully with the result of `op`. > +/// Otherwise, it waits for a duration specified by `sleep_delta` > +/// before executing `op` again. > +/// This process continues until either `cond` returns `true` or the timeout, > +/// specified by `timeout_delta`, is reached. If `timeout_delta` is `None`, > +/// polling continues indefinitely until `cond` evaluates to `true` or an error occurs. > +/// > +/// # Examples > +/// > +/// ```rust,ignore > +/// fn wait_for_hardware(dev: &mut Device) -> Result<()> { > +/// // The `op` closure reads the value of a specific status register. > +/// let op = || -> Result<u16> { dev.read_ready_register() }; > +/// > +/// // The `cond` closure takes a reference to the value returned by `op` > +/// // and checks whether the hardware is ready. > +/// let cond = |val: &u16| *val == HW_READY; > +/// > +/// match read_poll_timeout(op, cond, Delta::from_millis(50), Some(Delta::from_secs(3))) { > +/// Ok(_) => { > +/// // The hardware is ready. The returned value of the `op`` closure isn't used. > +/// Ok(()) > +/// } > +/// Err(e) => Err(e), > +/// } > +/// } > +/// ``` > +/// > +/// ```rust > +/// use kernel::io::poll::read_poll_timeout; > +/// use kernel::time::Delta; > +/// use kernel::sync::{SpinLock, new_spinlock}; > +/// > +/// let lock = KBox::pin_init(new_spinlock!(()), kernel::alloc::flags::GFP_KERNEL)?; > +/// let g = lock.lock(); > +/// read_poll_timeout(|| Ok(()), |()| true, Delta::from_micros(42), Some(Delta::from_micros(42))); > +/// drop(g); > +/// > +/// # Ok::<(), Error>(()) > +/// ``` > +#[track_caller] > +pub fn read_poll_timeout<Op, Cond, T>( > + mut op: Op, > + mut cond: Cond, > + sleep_delta: Delta, > + timeout_delta: Option<Delta>, Fun idea I just had, though not sure it is of actuall use (probably not). Instead of `Option<Delta> we could use `impl Into<Option<Delta>>`, that enables to use both, so not having to write Some if we have a value. > +) -> Result<T> > +where > + Op: FnMut() -> Result<T>, > + Cond: FnMut(&T) -> bool, > +{ > + let start = Instant::now(); > + let sleep = !sleep_delta.is_zero(); > + > + if sleep { > + might_sleep(); > + } > + > + loop { > + let val = op()?; > + if cond(&val) { > + // Unlike the C version, we immediately return. > + // We know the condition is met so we don't need to check again. > + return Ok(val); > + } > + if let Some(timeout_delta) = timeout_delta { > + if start.elapsed() > timeout_delta { > + // Unlike the C version, we immediately return. > + // We have just called `op()` so we don't need to call it again. > + return Err(ETIMEDOUT); > + } > + } > + if sleep { > + fsleep(sleep_delta); > + } > + // fsleep() could be busy-wait loop so we always call cpu_relax(). > + cpu_relax(); > + } > +} > + > +/// Annotation for functions that can sleep. > +/// > +/// Equivalent to the C side [`might_sleep()`], this function serves as > +/// a debugging aid and a potential scheduling point. > +/// > +/// This function can only be used in a nonatomic context. > +#[track_caller] > +fn might_sleep() { > + #[cfg(CONFIG_DEBUG_ATOMIC_SLEEP)] > + { > + let loc = core::panic::Location::caller(); > + // SAFETY: FFI call. > + unsafe { > + crate::bindings::__might_sleep_precision( > + loc.file().as_ptr().cast(), > + loc.file().len() as i32, > + loc.line() as i32, > + ) > + } > + } > + > + // SAFETY: FFI call. > + unsafe { crate::bindings::might_resched() } > +} > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs > index 496ed32b0911..415c500212dd 100644 > --- a/rust/kernel/lib.rs > +++ b/rust/kernel/lib.rs > @@ -40,6 +40,7 @@ > pub mod block; > #[doc(hidden)] > pub mod build_assert; > +pub mod cpu; > pub mod cred; > pub mod device; > pub mod device_id;
On Thu, 20 Feb 2025 16:04:50 +0100 Fiona Behrens <me@kloenk.dev> wrote: >> Add read_poll_timeout functions which poll periodically until a >> condition is met or a timeout is reached. >> >> The C's read_poll_timeout (include/linux/iopoll.h) is a complicated >> macro and a simple wrapper for Rust doesn't work. So this implements >> the same functionality in Rust. >> >> The C version uses usleep_range() while the Rust version uses >> fsleep(), which uses the best sleep method so it works with spans that >> usleep_range() doesn't work nicely with. >> >> The sleep_before_read argument isn't supported since there is no user >> for now. It's rarely used in the C version. >> >> read_poll_timeout() 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] >> Tested-by: Daniel Almeida <daniel.almeida@collabora.com> >> Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com> > > Reviewed-by: Fiona Behrens <me@kloenk.dev> Thanks! >> +#[track_caller] >> +pub fn read_poll_timeout<Op, Cond, T>( >> + mut op: Op, >> + mut cond: Cond, >> + sleep_delta: Delta, >> + timeout_delta: Option<Delta>, > > Fun idea I just had, though not sure it is of actuall use (probably not). > Instead of `Option<Delta> we could use `impl Into<Option<Delta>>`, > that enables to use both, so not having to write Some if we have a value. Either is fine by me. I couldn't find any functions under the rust/kernel that use impl Into<Option<T>> as an argument. Any rules regarding this?
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index 9565485a1a54..16d256897ccb 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -14,6 +14,7 @@ #include "cred.c" #include "device.c" #include "err.c" +#include "kernel.c" #include "fs.c" #include "io.c" #include "jump_label.c" diff --git a/rust/helpers/kernel.c b/rust/helpers/kernel.c new file mode 100644 index 000000000000..f04c04d4cc4f --- /dev/null +++ b/rust/helpers/kernel.c @@ -0,0 +1,18 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/kernel.h> + +void rust_helper_cpu_relax(void) +{ + cpu_relax(); +} + +void rust_helper___might_sleep_precision(const char *file, int len, int line) +{ + __might_sleep_precision(file, len, line); +} + +void rust_helper_might_resched(void) +{ + might_resched(); +} diff --git a/rust/kernel/cpu.rs b/rust/kernel/cpu.rs new file mode 100644 index 000000000000..eeeff4be84fa --- /dev/null +++ b/rust/kernel/cpu.rs @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Processor related primitives. +//! +//! C header: [`include/linux/processor.h`](srctree/include/linux/processor.h). + +/// Lower CPU power consumption or yield to a hyperthreaded twin processor. +/// +/// It also happens to serve as a compiler barrier. +pub fn cpu_relax() { + // SAFETY: FFI call. + unsafe { bindings::cpu_relax() } +} diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs index f6ecf09cb65f..8858eb13b3df 100644 --- a/rust/kernel/error.rs +++ b/rust/kernel/error.rs @@ -64,6 +64,7 @@ macro_rules! declare_err { declare_err!(EPIPE, "Broken pipe."); declare_err!(EDOM, "Math argument out of domain of func."); declare_err!(ERANGE, "Math result not representable."); + declare_err!(ETIMEDOUT, "Connection timed out."); declare_err!(ERESTARTSYS, "Restart the system call."); declare_err!(ERESTARTNOINTR, "System call was interrupted by a signal and will be restarted."); declare_err!(ERESTARTNOHAND, "Restart if no handler."); diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs index d4a73e52e3ee..be63742f517b 100644 --- a/rust/kernel/io.rs +++ b/rust/kernel/io.rs @@ -7,6 +7,8 @@ use crate::error::{code::EINVAL, Result}; use crate::{bindings, build_assert}; +pub mod poll; + /// Raw representation of an MMIO region. /// /// By itself, the existence of an instance of this structure does not provide any guarantees that diff --git a/rust/kernel/io/poll.rs b/rust/kernel/io/poll.rs new file mode 100644 index 000000000000..5977b2082cc6 --- /dev/null +++ b/rust/kernel/io/poll.rs @@ -0,0 +1,120 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! IO polling. +//! +//! C header: [`include/linux/iopoll.h`](srctree/include/linux/iopoll.h). + +use crate::{ + cpu::cpu_relax, + error::{code::*, Result}, + time::{delay::fsleep, Delta, Instant}, +}; + +/// Polls periodically until a condition is met or a timeout is reached. +/// +/// The function repeatedly executes the given operation `op` closure and +/// checks its result using the condition closure `cond`. +/// If `cond` returns `true`, the function returns successfully with the result of `op`. +/// Otherwise, it waits for a duration specified by `sleep_delta` +/// before executing `op` again. +/// This process continues until either `cond` returns `true` or the timeout, +/// specified by `timeout_delta`, is reached. If `timeout_delta` is `None`, +/// polling continues indefinitely until `cond` evaluates to `true` or an error occurs. +/// +/// # Examples +/// +/// ```rust,ignore +/// fn wait_for_hardware(dev: &mut Device) -> Result<()> { +/// // The `op` closure reads the value of a specific status register. +/// let op = || -> Result<u16> { dev.read_ready_register() }; +/// +/// // The `cond` closure takes a reference to the value returned by `op` +/// // and checks whether the hardware is ready. +/// let cond = |val: &u16| *val == HW_READY; +/// +/// match read_poll_timeout(op, cond, Delta::from_millis(50), Some(Delta::from_secs(3))) { +/// Ok(_) => { +/// // The hardware is ready. The returned value of the `op`` closure isn't used. +/// Ok(()) +/// } +/// Err(e) => Err(e), +/// } +/// } +/// ``` +/// +/// ```rust +/// use kernel::io::poll::read_poll_timeout; +/// use kernel::time::Delta; +/// use kernel::sync::{SpinLock, new_spinlock}; +/// +/// let lock = KBox::pin_init(new_spinlock!(()), kernel::alloc::flags::GFP_KERNEL)?; +/// let g = lock.lock(); +/// read_poll_timeout(|| Ok(()), |()| true, Delta::from_micros(42), Some(Delta::from_micros(42))); +/// drop(g); +/// +/// # Ok::<(), Error>(()) +/// ``` +#[track_caller] +pub fn read_poll_timeout<Op, Cond, T>( + mut op: Op, + mut cond: Cond, + sleep_delta: Delta, + timeout_delta: Option<Delta>, +) -> Result<T> +where + Op: FnMut() -> Result<T>, + Cond: FnMut(&T) -> bool, +{ + let start = Instant::now(); + let sleep = !sleep_delta.is_zero(); + + if sleep { + might_sleep(); + } + + loop { + let val = op()?; + if cond(&val) { + // Unlike the C version, we immediately return. + // We know the condition is met so we don't need to check again. + return Ok(val); + } + if let Some(timeout_delta) = timeout_delta { + if start.elapsed() > timeout_delta { + // Unlike the C version, we immediately return. + // We have just called `op()` so we don't need to call it again. + return Err(ETIMEDOUT); + } + } + if sleep { + fsleep(sleep_delta); + } + // fsleep() could be busy-wait loop so we always call cpu_relax(). + cpu_relax(); + } +} + +/// Annotation for functions that can sleep. +/// +/// Equivalent to the C side [`might_sleep()`], this function serves as +/// a debugging aid and a potential scheduling point. +/// +/// This function can only be used in a nonatomic context. +#[track_caller] +fn might_sleep() { + #[cfg(CONFIG_DEBUG_ATOMIC_SLEEP)] + { + let loc = core::panic::Location::caller(); + // SAFETY: FFI call. + unsafe { + crate::bindings::__might_sleep_precision( + loc.file().as_ptr().cast(), + loc.file().len() as i32, + loc.line() as i32, + ) + } + } + + // SAFETY: FFI call. + unsafe { crate::bindings::might_resched() } +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 496ed32b0911..415c500212dd 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -40,6 +40,7 @@ pub mod block; #[doc(hidden)] pub mod build_assert; +pub mod cpu; pub mod cred; pub mod device; pub mod device_id;