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Mon, 13 Jul 2026 18:52:44 -0400 (EDT) From: FUJITA Tomonori To: a.hindborg@kernel.org, ojeda@kernel.org Cc: acourbot@nvidia.com, aliceryhl@google.com, anna-maria@linutronix.de, bjorn3_gh@protonmail.com, boqun@kernel.org, dakr@kernel.org, daniel.almeida@collabora.com, frederic@kernel.org, gary@garyguo.net, jstultz@google.com, lossin@kernel.org, lyude@redhat.com, sboyd@kernel.org, tamird@kernel.org, tglx@kernel.org, tmgross@umich.edu, work@onurozkan.dev, rust-for-linux@vger.kernel.org, FUJITA Tomonori Subject: [PATCH v1] rust: time: fix as_micros_ceil() to round correctly for negative Delta Date: Tue, 14 Jul 2026 07:52:35 +0900 Message-ID: <20260713225235.3243480-1-tomo@flapping.org> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: FUJITA Tomonori The ceiling-division idiom `(n + d - 1) / d` only produces the correct result when `n` is non-negative. For example, if n = -1000 (exactly -1us), the old code computed (-1000 + 999) / 1000 == 0 instead of -1. For negative n, truncating division already rounds towards positive infinity, so no bias is needed in that case. Fixes: fae0cdc12340 ("rust: time: Introduce Delta type") Signed-off-by: FUJITA Tomonori --- rust/kernel/time.rs | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs index 363e93cbb139..b8463823aed9 100644 --- a/rust/kernel/time.rs +++ b/rust/kernel/time.rs @@ -441,15 +441,22 @@ pub const fn as_nanos(self) -> i64 { /// to the value in the [`Delta`]. #[inline] pub fn as_micros_ceil(self) -> i64 { + let n = self.as_nanos(); + let n = if n >= 0 { + n.saturating_add(NSEC_PER_USEC - 1) + } else { + n + }; + #[cfg(CONFIG_64BIT)] { - self.as_nanos().saturating_add(NSEC_PER_USEC - 1) / NSEC_PER_USEC + n / NSEC_PER_USEC } #[cfg(not(CONFIG_64BIT))] // SAFETY: It is always safe to call `ktime_to_us()` with any value. unsafe { - bindings::ktime_to_us(self.as_nanos().saturating_add(NSEC_PER_USEC - 1)) + bindings::ktime_to_us(n) } } base-commit: 5a81c35c3b18cd59ded56171a6a9f643b92a6759 -- 2.43.0