From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f73.google.com (mail-wr1-f73.google.com [209.85.221.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A6F4F31D38A for ; Fri, 9 Jan 2026 08:23:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767947000; cv=none; b=sQMcf4rpol4RZDRVBoo+1TeP7IqJaB/LVr1MgC4S98wKBNnkcEtc6DnYvf7XBcck9wsG+qsNg3Zdx7MttSBFjuMgf2nBPJI3iuI0Q9Dm+8dKHxrY5wDUMFMzA+x+aSKb5mu9zUNKQPVafQtGiU1SfBy4ef8u39triseaSPgPl1c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767947000; c=relaxed/simple; bh=vBPt4h3wZHY2UNtA6qX2YDSxcBcfgilmBq2e3leduG4=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Iim7Z0PvqriSmdzp0B249KwRvOriKbu4d94ul1c8ZyuP31Nu+6AKV2JS3KQbV6CdBF5WOFLiGIgNxEIZYEDqXxwej648RGzjityUYRGvc3cAF+4iaj7yI6J1vUFEaC11SRW5hhvXxQCBC+g5lY33P0SgQ8xlSHS4+05EwcfojEc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=ZlUcKXIQ; arc=none smtp.client-ip=209.85.221.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ZlUcKXIQ" Received: by mail-wr1-f73.google.com with SMTP id ffacd0b85a97d-432a9ef3d86so2072417f8f.2 for ; Fri, 09 Jan 2026 00:23:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1767946985; x=1768551785; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=k+OIYQwN5Lnpy5XafsdsgLoQcdxRCARoCXPEgNNxga4=; b=ZlUcKXIQbDvZfPppyw8bxVFE3OvYEaQWsebPZjYQmMfVBpD4l72sL0UQWi0qMsTnE3 jo4uLTuGpSOtRCMlYFImfeTTUjfLCOpRf6J6AfeguEZnFDiQfQ2JpcZHL+YvfwQgWfGC MfK2kbreCJ5LdUCR/kSr6SegCRM5m/EsEKFWn8JYVI9PlMlo0CSz40MYCoUVE+6+43ii ey3hpq3hDgE05r02zBeCfXCEF+fOEmKKbAp0TUA8gcBIpAa0J2Zp1nNaNQZfj5MnY2WM RDGcEIF7zrth9gfURjtwqEVNm2GlNqlycbX+2/sZMucIQLlAmmM+QWIGfIZODq81ua/8 hv3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1767946985; x=1768551785; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=k+OIYQwN5Lnpy5XafsdsgLoQcdxRCARoCXPEgNNxga4=; b=LITePgQ92/050ETjA8cq896kQJ87aFgqvbXAxYFUUnqTgPLE1SFTDb1inJtCAi5oYN yf3oof09uUNezQH0rytGpr3Fut6qtIz3jOScyhe0JfVMpAtk5uBxYA4PM+t26AEsJE+F MP3F2sZ59Lip6bxXZoenI5uxlcuiYOlD6U/ZzBYm4v4PGUD4QUg6PZ515L9jKBJfQESV lWnMq0QfoL73Ms+V94PbBFzL4s1Rxe94hLb2sPMPRzDAVlVwtVS0ARVFVm3JqnhIqvaE EsiiOJxWwMacQfR0nTIqSiAeidH2WOXU8FH878wsPDjDxyuFYYAtuugst0ZoKSUBL2C2 jRpw== X-Forwarded-Encrypted: i=1; AJvYcCUnAq55f0klio3AErcXe24YA7Yn33BOifBs728xrhQWk8/8ByAponQgK4lgCw6PTyzWCZ6StN3B1+VLiiy/IA==@vger.kernel.org X-Gm-Message-State: AOJu0Yx0jKLNlXDYSblE7BryeuFuYND8HxpTB8kEmUFS89w2JgJC+wde dXvrcZE2tF6GWrii8W/U9ZYuZrV7XMq+b8OMvdWD+vPOUvHagtgyGVvD9YOPDg4thNzIN60fay3 rPZQqWnHPL4SCkkJAHA== X-Google-Smtp-Source: AGHT+IE7U59bnurv+WF3qIn8ev80ktuI3hTbWJPBTAuiBuCmwkciUQLwJTbfII0vWKYLFARalICFMpRepoekZpU= X-Received: from wrbgw11.prod.google.com ([2002:a05:6000:40cb:b0:42c:c2d6:2a3]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:144c:b0:42f:9e75:8605 with SMTP id ffacd0b85a97d-432c32f5a84mr9154998f8f.0.1767946985172; Fri, 09 Jan 2026 00:23:05 -0800 (PST) Date: Fri, 9 Jan 2026 08:23:04 +0000 In-Reply-To: <20260109.093641.1161098806794561807.fujita.tomonori@gmail.com> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260108125005.2945800-1-fujita.tomonori@gmail.com> <20260109.093641.1161098806794561807.fujita.tomonori@gmail.com> Message-ID: Subject: Re: [PATCH v2] rust: sync: atomic: Add i32-backed Flag for atomic booleans From: Alice Ryhl To: FUJITA Tomonori Cc: boqun.feng@gmail.com, ojeda@kernel.org, peterz@infradead.org, will@kernel.org, a.hindborg@kernel.org, bjorn3_gh@protonmail.com, dakr@kernel.org, gary@garyguo.net, lossin@kernel.org, mark.rutland@arm.com, tmgross@umich.edu, rust-for-linux@vger.kernel.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Fri, Jan 09, 2026 at 09:36:41AM +0900, FUJITA Tomonori wrote: > On Thu, 8 Jan 2026 13:54:58 +0100 > Alice Ryhl wrote: >=20 > > On Thu, Jan 8, 2026 at 1:50=E2=80=AFPM FUJITA Tomonori > > wrote: > >> > >> Add a new Flag enum (Clear/Set) and implement AtomicType for it, so > >> users can use Atomic for boolean flags. > >> > >> The backing integer type is an implementation detail; it is currently > >> i32 but may change in the future. > >> > >> Document when Atomic is generally preferable to Atomic: in > >> particular, when RMW operations such as xchg()/cmpxchg() may be used > >> and minimizing memory usage is not the top priority. On some > >> architectures without byte-sized RMW instructions, Atomic can be > >> slower for RMW operations. > >> > >> Signed-off-by: FUJITA Tomonori > >=20 > > Can we have a `struct AtomicFlag(Atomic)` here whose load() / > > store() methods use real booleans? Otherwise this seems inconvenient > > to use. >=20 > Do you mean something along these lines? >=20 > diff --git a/rust/kernel/sync/atomic.rs b/rust/kernel/sync/atomic.rs > index 473d3c07e234..19750be1a239 100644 > --- a/rust/kernel/sync/atomic.rs > +++ b/rust/kernel/sync/atomic.rs > @@ -622,3 +622,29 @@ fn from(b: bool) -> Self { > } > } > } > + > +/// A convenience wrapper around [`Atomic`] that exposes a `bool` = API. > +pub struct AtomicFlag(Atomic); > + > +impl AtomicFlag { > + /// Creates a new atomic flag. > + pub const fn new(b: bool) -> Self { > + if b { > + AtomicFlag(Atomic::new(Flag::Set)) > + } else { > + AtomicFlag(Atomic::new(Flag::Clear)) > + } > + } > + > + /// Loads the value from the atomic flag. > + #[inline(always)] > + pub fn load(&self, o: Ordering= ) -> bool { > + self.0.load(o).into() > + } > + > + /// Stores a value to the atomic flag. > + #[inline(always)] > + pub fn store(&self, b: bool, o= : Ordering) { > + self.0.store(b.into(), o) > + } > +} Yes, that's what I meant. Alice