| Message ID | 20250125101854.112261-8-fujita.tomonori@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | rust: Add IO polling | expand |
On Sat, 25 Jan 2025 19:18:52 +0900 FUJITA Tomonori <fujita.tomonori@gmail.com> 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. > > Unlike the C version, __might_sleep() is used instead of might_sleep() > to show proper debug info; the file name and line > number. might_resched() could be added to match what the C version > does but this function works without it. > > 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] > Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com> > --- > rust/helpers/helpers.c | 1 + > rust/helpers/kernel.c | 13 +++++++ > rust/kernel/cpu.rs | 13 +++++++ > rust/kernel/error.rs | 1 + > rust/kernel/io.rs | 5 +++ > rust/kernel/io/poll.rs | 79 ++++++++++++++++++++++++++++++++++++++++++ > rust/kernel/lib.rs | 2 ++ > 7 files changed, 114 insertions(+) > create mode 100644 rust/helpers/kernel.c > create mode 100644 rust/kernel/cpu.rs > create mode 100644 rust/kernel/io.rs > create mode 100644 rust/kernel/io/poll.rs > > diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c > index d16aeda7a558..7ab71a6d4603 100644 > --- a/rust/helpers/helpers.c > +++ b/rust/helpers/helpers.c > @@ -13,6 +13,7 @@ > #include "build_bug.c" > #include "cred.c" > #include "err.c" > +#include "kernel.c" > #include "fs.c" > #include "jump_label.c" > #include "kunit.c" > diff --git a/rust/helpers/kernel.c b/rust/helpers/kernel.c > new file mode 100644 > index 000000000000..9dff28f4618e > --- /dev/null > +++ b/rust/helpers/kernel.c > @@ -0,0 +1,13 @@ > +// 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); > +} > 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 > new file mode 100644 > index 000000000000..033f3c4e4adf > --- /dev/null > +++ b/rust/kernel/io.rs > @@ -0,0 +1,5 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +//! Input and Output. > + > +pub mod poll; > diff --git a/rust/kernel/io/poll.rs b/rust/kernel/io/poll.rs > new file mode 100644 > index 000000000000..7a503cf643a1 > --- /dev/null > +++ b/rust/kernel/io/poll.rs > @@ -0,0 +1,79 @@ > +// 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}, > +}; > + > +use core::panic::Location; > + > +/// Polls periodically until a condition is met or a timeout is reached. > +/// > +/// Public but hidden since it should only be used from public macros. > +/// > +/// ```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), Delta::from_micros(42)); > +/// drop(g); > +/// > +/// # Ok::<(), Error>(()) > +/// ``` > +#[track_caller] > +pub fn read_poll_timeout<Op, Cond, T: Copy>( > + mut op: Op, > + mut cond: Cond, > + sleep_delta: Delta, > + timeout_delta: Delta, > +) -> Result<T> > +where > + Op: FnMut() -> Result<T>, > + Cond: FnMut(&T) -> bool, > +{ > + let start = Instant::now(); > + let sleep = !sleep_delta.is_zero(); > + let timeout = !timeout_delta.is_zero(); > + > + if sleep { > + might_sleep(Location::caller()); > + } > + > + 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 timeout && start.elapsed() > timeout_delta { Re-reading this again I wonder if this is the desired behaviour? Maybe a timeout of 0 should mean check-once instead of no timeout. The special-casing of 0 makes sense in C but in Rust we should use `None` to mean it instead? For `sleep_delta` it's fine to not use `Option`. > + // 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(); > + } > +} > + > +fn might_sleep(loc: &Location<'_>) { > + // SAFETY: FFI call. > + unsafe { > + crate::bindings::__might_sleep_precision( > + loc.file().as_ptr().cast(), > + loc.file().len() as i32, > + loc.line() as i32, > + ) > + } > +} > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs > index 545d1170ee63..c477701b2efa 100644 > --- a/rust/kernel/lib.rs > +++ b/rust/kernel/lib.rs > @@ -35,6 +35,7 @@ > pub mod block; > #[doc(hidden)] > pub mod build_assert; > +pub mod cpu; > pub mod cred; > pub mod device; > pub mod error; > @@ -42,6 +43,7 @@ > pub mod firmware; > pub mod fs; > pub mod init; > +pub mod io; > pub mod ioctl; > pub mod jump_label; > #[cfg(CONFIG_KUNIT)]
On Mon, 27 Jan 2025 11:46:46 +0800 Gary Guo <gary@garyguo.net> wrote: >> +#[track_caller] >> +pub fn read_poll_timeout<Op, Cond, T: Copy>( >> + mut op: Op, >> + mut cond: Cond, >> + sleep_delta: Delta, >> + timeout_delta: Delta, >> +) -> Result<T> >> +where >> + Op: FnMut() -> Result<T>, >> + Cond: FnMut(&T) -> bool, >> +{ >> + let start = Instant::now(); >> + let sleep = !sleep_delta.is_zero(); >> + let timeout = !timeout_delta.is_zero(); >> + >> + if sleep { >> + might_sleep(Location::caller()); >> + } >> + >> + 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 timeout && start.elapsed() > timeout_delta { > > Re-reading this again I wonder if this is the desired behaviour? Maybe > a timeout of 0 should mean check-once instead of no timeout. The > special-casing of 0 makes sense in C but in Rust we should use `None` > to mean it instead? It's the behavior of the C version; the comment of this function says: * @timeout_us: Timeout in us, 0 means never timeout You meant that waiting for a condition without a timeout is generally a bad idea? If so, can we simply return EINVAL for zero Delta?
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index d16aeda7a558..7ab71a6d4603 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -13,6 +13,7 @@ #include "build_bug.c" #include "cred.c" #include "err.c" +#include "kernel.c" #include "fs.c" #include "jump_label.c" #include "kunit.c" diff --git a/rust/helpers/kernel.c b/rust/helpers/kernel.c new file mode 100644 index 000000000000..9dff28f4618e --- /dev/null +++ b/rust/helpers/kernel.c @@ -0,0 +1,13 @@ +// 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); +} 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 new file mode 100644 index 000000000000..033f3c4e4adf --- /dev/null +++ b/rust/kernel/io.rs @@ -0,0 +1,5 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Input and Output. + +pub mod poll; diff --git a/rust/kernel/io/poll.rs b/rust/kernel/io/poll.rs new file mode 100644 index 000000000000..7a503cf643a1 --- /dev/null +++ b/rust/kernel/io/poll.rs @@ -0,0 +1,79 @@ +// 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}, +}; + +use core::panic::Location; + +/// Polls periodically until a condition is met or a timeout is reached. +/// +/// Public but hidden since it should only be used from public macros. +/// +/// ```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), Delta::from_micros(42)); +/// drop(g); +/// +/// # Ok::<(), Error>(()) +/// ``` +#[track_caller] +pub fn read_poll_timeout<Op, Cond, T: Copy>( + mut op: Op, + mut cond: Cond, + sleep_delta: Delta, + timeout_delta: Delta, +) -> Result<T> +where + Op: FnMut() -> Result<T>, + Cond: FnMut(&T) -> bool, +{ + let start = Instant::now(); + let sleep = !sleep_delta.is_zero(); + let timeout = !timeout_delta.is_zero(); + + if sleep { + might_sleep(Location::caller()); + } + + 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 timeout && 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(); + } +} + +fn might_sleep(loc: &Location<'_>) { + // SAFETY: FFI call. + unsafe { + crate::bindings::__might_sleep_precision( + loc.file().as_ptr().cast(), + loc.file().len() as i32, + loc.line() as i32, + ) + } +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 545d1170ee63..c477701b2efa 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -35,6 +35,7 @@ pub mod block; #[doc(hidden)] pub mod build_assert; +pub mod cpu; pub mod cred; pub mod device; pub mod error; @@ -42,6 +43,7 @@ pub mod firmware; pub mod fs; pub mod init; +pub mod io; pub mod ioctl; pub mod jump_label; #[cfg(CONFIG_KUNIT)]
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. Unlike the C version, __might_sleep() is used instead of might_sleep() to show proper debug info; the file name and line number. might_resched() could be added to match what the C version does but this function works without it. 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] Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com> --- rust/helpers/helpers.c | 1 + rust/helpers/kernel.c | 13 +++++++ rust/kernel/cpu.rs | 13 +++++++ rust/kernel/error.rs | 1 + rust/kernel/io.rs | 5 +++ rust/kernel/io/poll.rs | 79 ++++++++++++++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 2 ++ 7 files changed, 114 insertions(+) create mode 100644 rust/helpers/kernel.c create mode 100644 rust/kernel/cpu.rs create mode 100644 rust/kernel/io.rs create mode 100644 rust/kernel/io/poll.rs