From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3DFB7260578 for ; Thu, 24 Jul 2025 18:57:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753383443; cv=none; b=Wu+RhZAxo8DH1mwK+4tVB++bgxw9cX8JuyS3TqYpFSI5mNld2MDcjpjRE9qMCGI3UU3aomw82qxhI2007Jt0EYdUqdICEH+rqCxTHy2xT2sny+MVrTgVdP4nzQpTPS9QyoDrknQr6TMKQJZ/to/UY0ha/QI8VR5S6hhzL6KALu0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753383443; c=relaxed/simple; bh=WiRKoW3jEqRtZjwGPjsFDVXe43IHCEGeVUZFIvWIvuw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Lw5SS+H/8liI2z4gPvO4tl4ie4Cb4ZwqyWdh18EFhVEGkft9ohdX1mQjtWG248sKuHHXZhf7oIAXTNJ87dVq9QanI3+dnCAIrhPL1dbqy8kA4pLgAJg1GZ7CF/HHUsqq7MjsNDcgi/vQTt51YFTkojRj1LTdMwgEyB1Ffb9IscQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=SvT7mjVc; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SvT7mjVc" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753383441; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4JYSxMYzK9rXZpTAuUNhhgT+UnDZ1iR5Hu7L994nIeI=; b=SvT7mjVcYY92wl/+atbdhtJLzyKKau6ZCldpbIvzH2PUcjDERjxJ4bqSSwYaEfH647wgxT 9Vr9kigy1bJM/IaN3MOq1J/2OjQIwhNsva2mH+3BdGlexgphUT3QwaGwmxZOySrJ9hV3ay /Oz868RSXsSdkz3dGWqRbdap5gfKucY= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-480-0CFra9ivPg-qFj64AQlijw-1; Thu, 24 Jul 2025 14:57:17 -0400 X-MC-Unique: 0CFra9ivPg-qFj64AQlijw-1 X-Mimecast-MFC-AGG-ID: 0CFra9ivPg-qFj64AQlijw_1753383435 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2724F1800359; Thu, 24 Jul 2025 18:57:15 +0000 (UTC) Received: from chopper.lyude.net (unknown [10.22.88.223]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 148CE195608D; Thu, 24 Jul 2025 18:57:10 +0000 (UTC) From: Lyude Paul To: rust-for-linux@vger.kernel.org, Thomas Gleixner , Boqun Feng , linux-kernel@vger.kernel.org, Andreas Hindborg , FUJITA Tomonori Cc: Frederic Weisbecker , Anna-Maria Behnsen , John Stultz , Stephen Boyd , Miguel Ojeda , Alex Gaynor , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Alice Ryhl , Trevor Gross , Danilo Krummrich Subject: [PATCH 1/2] rust: time: Implement Add/Sub for Instant Date: Thu, 24 Jul 2025 14:54:06 -0400 Message-ID: <20250724185700.557505-2-lyude@redhat.com> In-Reply-To: <20250724185700.557505-1-lyude@redhat.com> References: <20250724185700.557505-1-lyude@redhat.com> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 In order to maintain the invariants of Instant, we use saturating addition/subtraction that is clamped to the valid value range for a non-negative Ktime. Signed-off-by: Lyude Paul --- rust/kernel/time.rs | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs index 64c8dcf548d63..ac5cab62070c6 100644 --- a/rust/kernel/time.rs +++ b/rust/kernel/time.rs @@ -25,6 +25,7 @@ //! C header: [`include/linux/ktime.h`](srctree/include/linux/ktime.h). use core::marker::PhantomData; +use core::ops; pub mod delay; pub mod hrtimer; @@ -202,7 +203,7 @@ pub(crate) fn as_nanos(&self) -> i64 { } } -impl core::ops::Sub for Instant { +impl ops::Sub for Instant { type Output = Delta; // By the type invariant, it never overflows. @@ -214,6 +215,32 @@ fn sub(self, other: Instant) -> Delta { } } +impl ops::Add for Instant { + type Output = Self; + + #[inline] + fn add(self, rhs: Delta) -> Self::Output { + // INVARIANT: We clamp the resulting value to be between `0` and `KTIME_MAX`. + Self { + inner: self.inner.saturating_add(rhs.nanos).clamp(0, i64::MAX), + _c: PhantomData, + } + } +} + +impl ops::Sub for Instant { + type Output = Self; + + #[inline] + fn sub(self, rhs: Delta) -> Self::Output { + // INVARIANT: We clamp the resulting value to be between `0` and `KTIME_MAX`. + Self { + inner: self.inner.saturating_sub(rhs.nanos).clamp(0, i64::MAX), + _c: PhantomData, + } + } +} + /// A span of time. /// /// This struct represents a span of time, with its value stored as nanoseconds. -- 2.50.0