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[180.15.148.177]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-ad51ea79a47sm2877843a12.76.2025.02.07.05.31.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Feb 2025 05:32:03 -0800 (PST) From: FUJITA Tomonori To: linux-kernel@vger.kernel.org Cc: Gary Guo , Alice Ryhl , Fiona Behrens , rust-for-linux@vger.kernel.org, netdev@vger.kernel.org, andrew@lunn.ch, hkallweit1@gmail.com, tmgross@umich.edu, ojeda@kernel.org, alex.gaynor@gmail.com, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@samsung.com, anna-maria@linutronix.de, frederic@kernel.org, tglx@linutronix.de, arnd@arndb.de, jstultz@google.com, sboyd@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, tgunders@redhat.com Subject: [PATCH v10 5/8] rust: time: Add wrapper for fsleep() function Date: Fri, 7 Feb 2025 22:26:20 +0900 Message-ID: <20250207132623.168854-6-fujita.tomonori@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250207132623.168854-1-fujita.tomonori@gmail.com> References: <20250207132623.168854-1-fujita.tomonori@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add 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] Reviewed-by: Gary Guo Reviewed-by: Alice Ryhl Reviewed-by: Fiona Behrens Signed-off-by: FUJITA Tomonori --- 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 0640b7e115be..9565485a1a54 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -31,6 +31,7 @@ #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 + +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) + } +}