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[180.53.81.189]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7205791db5fsm180188b3a.11.2024.10.24.20.34.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Oct 2024 20:34:32 -0700 (PDT) From: FUJITA Tomonori To: anna-maria@linutronix.de, frederic@kernel.org, tglx@linutronix.de, jstultz@google.com, sboyd@kernel.org, linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org, rust-for-linux@vger.kernel.org, andrew@lunn.ch, hkallweit1@gmail.com, tmgross@umich.edu, ojeda@kernel.org, alex.gaynor@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@samsung.com, aliceryhl@google.com, arnd@arndb.de Subject: [PATCH v4 6/7] rust: Add read_poll_timeout functions Date: Fri, 25 Oct 2024 12:31:17 +0900 Message-ID: <20241025033118.44452-7-fujita.tomonori@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20241025033118.44452-1-fujita.tomonori@gmail.com> References: <20241025033118.44452-1-fujita.tomonori@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add read_poll_timeout functions which poll periodically until a condition is met or a timeout is reached. 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. For the proper debug info, readx_poll_timeout() and __might_sleep() are implemented as a macro. We could implement them as a normal function if there is a clean way to get a null-terminated string without allocation from core::panic::Location::file(). readx_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 --- rust/helpers/helpers.c | 1 + rust/helpers/kernel.c | 13 ++++++ rust/kernel/error.rs | 1 + rust/kernel/io.rs | 5 +++ rust/kernel/io/poll.rs | 93 ++++++++++++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 2 + rust/kernel/processor.rs | 13 ++++++ 7 files changed, 128 insertions(+) create mode 100644 rust/helpers/kernel.c create mode 100644 rust/kernel/io.rs create mode 100644 rust/kernel/io/poll.rs create mode 100644 rust/kernel/processor.rs diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index c274546bcf78..f9569ff1717e 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -12,6 +12,7 @@ #include "build_assert.c" #include "build_bug.c" #include "err.c" +#include "kernel.c" #include "kunit.c" #include "mutex.c" #include "page.c" diff --git a/rust/helpers/kernel.c b/rust/helpers/kernel.c new file mode 100644 index 000000000000..da847059260b --- /dev/null +++ b/rust/helpers/kernel.c @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +void rust_helper_cpu_relax(void) +{ + cpu_relax(); +} + +void rust_helper___might_sleep(const char *file, int line) +{ + __might_sleep(file, line); +} diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs index 6f1587a2524e..d571b9587ed6 100644 --- a/rust/kernel/error.rs +++ b/rust/kernel/error.rs @@ -58,6 +58,7 @@ 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..ef1f38b59fda --- /dev/null +++ b/rust/kernel/io/poll.rs @@ -0,0 +1,93 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! IO polling. +//! +//! C header: [`include/linux/iopoll.h`](srctree/include/linux/iopoll.h). + +use crate::{ + error::{code::*, Result}, + processor::cpu_relax, + time::{delay::fsleep, Delta, Instant}, +}; + +/// Polls periodically until a condition is met or a timeout is reached. +/// +/// Public but hidden since it should only be used from public macros. +#[doc(hidden)] +pub fn read_poll_timeout( + mut op: Op, + cond: Cond, + sleep_delta: Delta, + timeout_delta: Delta, +) -> Result +where + Op: FnMut() -> Result, + Cond: Fn(T) -> bool, +{ + let start = Instant::now(); + let sleep = !sleep_delta.is_zero(); + let timeout = !timeout_delta.is_zero(); + + let val = loop { + let val = op()?; + if cond(val) { + // Unlike the C version, we immediately return. + // We know a condition is met so we don't need to check again. + return Ok(val); + } + if timeout && start.elapsed() > timeout_delta { + // Should we return Err(ETIMEDOUT) here instead of call op() again + // wihout a sleep between? But we follow the C version. op() could + // take some time so might be worth checking again. + break op()?; + } + if sleep { + fsleep(sleep_delta); + } + // fsleep() could be busy-wait loop so we always call cpu_relax(). + cpu_relax(); + }; + + if cond(val) { + Ok(val) + } else { + Err(ETIMEDOUT) + } +} + +/// Print debug information if it's called inside atomic sections. +#[macro_export] +macro_rules! __might_sleep { + () => { + #[cfg(CONFIG_DEBUG_ATOMIC_SLEEP)] + // SAFETY: FFI call. + unsafe { + $crate::bindings::__might_sleep( + c_str!(::core::file!()).as_char_ptr(), + ::core::line!() as i32, + ) + } + }; +} + +/// Polls periodically until a condition is met or a timeout is reached. +/// +/// `op` is called repeatedly until `cond` returns `true` or the timeout is +/// reached. The return value of `op` is passed to `cond`. +/// +/// `sleep_delta` is the duration to sleep between calls to `op`. +/// If `sleep_delta` is less than one microsecond, the function will busy-wait. +/// +/// `timeout_delta` is the maximum time to wait for `cond` to return `true`. +/// +/// This macro can only be used in a nonatomic context. +#[macro_export] +macro_rules! readx_poll_timeout { + ($op:expr, $cond:expr, $sleep_delta:expr, $timeout_delta:expr) => {{ + if !$sleep_delta.is_zero() { + $crate::__might_sleep!(); + } + + $crate::io::poll::read_poll_timeout($op, $cond, $sleep_delta, $timeout_delta) + }}; +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 22a3bfa5a9e9..b775fd1c9be0 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -35,6 +35,7 @@ #[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)] pub mod firmware; pub mod init; +pub mod io; pub mod ioctl; #[cfg(CONFIG_KUNIT)] pub mod kunit; @@ -44,6 +45,7 @@ pub mod page; pub mod prelude; pub mod print; +pub mod processor; pub mod sizes; pub mod rbtree; mod static_assert; diff --git a/rust/kernel/processor.rs b/rust/kernel/processor.rs new file mode 100644 index 000000000000..eeeff4be84fa --- /dev/null +++ b/rust/kernel/processor.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() } +}