From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from forward501a.mail.yandex.net (forward501a.mail.yandex.net [178.154.239.81]) (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 68B314A06; Sun, 7 Sep 2025 08:20:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.154.239.81 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757233219; cv=none; b=J02SLVZoM+g/E3/rraw79cJA5eXt1b0CxKMEhjJovrBkuRquvyEDy9Gepj9y9BretoQ+5diM2h7JvWsv+5vb3zfJj+n4BbtcEOYxxAkFzUP7goQEh+qbIViy48659gwUQ1/bI74o4E4fJbWi5qWqbBaB0Y8QxYR7KC24pcfZjig= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757233219; c=relaxed/simple; bh=WS/XaX3wOHVnhHAxGuafrPoemfTd0VcjPyTOVwJa9/0=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=iJnt2nUZ56k66f89lT4B8kv6Jbe6acEOWYXhzPU/o0qUsPdfH5m1tEMhyNVcKsJIqdnuLXTxKPMMkL7C8dmjnJCEU7+tYO9iYq2DPcXLpeVqFI6tgCaN897d5LXYkyX+gGTN41hMH84CpLJ06+N5FSgV7PobZFaTIftCFqNm5FM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=onurozkan.dev; spf=pass smtp.mailfrom=onurozkan.dev; dkim=pass (1024-bit key) header.d=onurozkan.dev header.i=@onurozkan.dev header.b=iCC6hcMA; arc=none smtp.client-ip=178.154.239.81 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=onurozkan.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=onurozkan.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=onurozkan.dev header.i=@onurozkan.dev header.b="iCC6hcMA" Received: from mail-nwsmtp-smtp-production-main-55.vla.yp-c.yandex.net (mail-nwsmtp-smtp-production-main-55.vla.yp-c.yandex.net [IPv6:2a02:6b8:c1f:582e:0:640:200:0]) by forward501a.mail.yandex.net (Yandex) with ESMTPS id A003D80AA3; Sun, 07 Sep 2025 11:20:12 +0300 (MSK) Received: by mail-nwsmtp-smtp-production-main-55.vla.yp-c.yandex.net (smtp/Yandex) with ESMTPSA id 6Kf8EwlM7Sw0-kg7N4O4m; Sun, 07 Sep 2025 11:20:11 +0300 X-Yandex-Fwd: 1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=onurozkan.dev; s=mail; t=1757233211; bh=P3ODHwoQxLQWBGEsy0K6883JH3EDCUD22i04tJTJsQY=; h=Cc:Message-ID:Subject:Date:References:To:From:In-Reply-To; b=iCC6hcMAi8K+Durc0iNlataiVZ6End/NhoDBj91SbRhk0RIW62hwwScz3Fqh2A7ny 2lL9Uxe/fakPIUjlVj57fIF39OnjaZ3HlABg5nf4bWcGt1FRFmpGJbK78QorxMgbsZ j0PecHPJW/jse/l4RaWTJVpe3OfMJK5s4JGsAW6U= Authentication-Results: mail-nwsmtp-smtp-production-main-55.vla.yp-c.yandex.net; dkim=pass header.i=@onurozkan.dev Date: Sun, 7 Sep 2025 11:20:06 +0300 From: Onur To: Daniel Almeida Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, lossin@kernel.org, lyude@redhat.com, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, dakr@kernel.org, peterz@infradead.org, mingo@redhat.com, will@kernel.org, longman@redhat.com, felipe_life@live.com, daniel@sedlak.dev, bjorn3_gh@protonmail.com Subject: Re: [PATCH v6 6/7] rust: ww_mutex/exec: add high-level API Message-ID: <20250907112006.6bdbb478@nimda.home> In-Reply-To: <2B16DBF4-1F6C-4025-8373-5651867B7D49@collabora.com> References: <20250903131313.4365-1-work@onurozkan.dev> <20250903131313.4365-7-work@onurozkan.dev> <6D30FEF7-07E7-4851-A7A2-76649AD0B217@collabora.com> <20250906141310.2c29aa8e@nimda.home> <2B16DBF4-1F6C-4025-8373-5651867B7D49@collabora.com> X-Mailer: Claws Mail 4.3.1 (GTK 3.24.50; x86_64-unknown-linux-gnu) Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Sat, 6 Sep 2025 12:04:34 -0300 Daniel Almeida wrote: >=20 >=20 > > On 6 Sep 2025, at 08:13, Onur wrote: > >=20 > > On Fri, 5 Sep 2025 16:42:09 -0300 > > Daniel Almeida wrote: > >=20 > >> Hi Onur, > >>=20 > >>> On 3 Sep 2025, at 10:13, Onur =C3=96zkan wrote: > >>>=20 > >>> `ExecContext` is a helper built on top of ww_mutex > >>=20 > >> Again, I wonder what people think about this particular name. > >>=20 > >>> that provides a retrying interface for lock acquisition. > >>> When `EDEADLK` is hit, it drops all held locks, resets > >>> the acquire context and retries the given (by the user) > >>> locking algorithm until it succeeds. > >>>=20 > >>> The API keeps track of acquired locks, cleans them up > >>> automatically and allows data access to the protected > >>> data through `with_locked()`. The `lock_all()` helper > >>> allows implementing multi-mutex algorithms in a simpler > >>> and less error-prone way while keeping the ww_mutex > >>> semantics. > >>>=20 > >>=20 > >> Great, this was exactly what I was looking for! :) > >>=20 > >>> Signed-off-by: Onur =C3=96zkan > >>> --- > >>> rust/kernel/sync/lock/ww_mutex.rs | 2 + > >>> rust/kernel/sync/lock/ww_mutex/exec.rs | 176 > >>> +++++++++++++++++++++++++ 2 files changed, 178 insertions(+) > >>> create mode 100644 rust/kernel/sync/lock/ww_mutex/exec.rs > >>>=20 > >>> diff --git a/rust/kernel/sync/lock/ww_mutex.rs > >>> b/rust/kernel/sync/lock/ww_mutex.rs index > >>> b415d6deae9b..7de6578513e5 100644 --- > >>> a/rust/kernel/sync/lock/ww_mutex.rs +++ > >>> b/rust/kernel/sync/lock/ww_mutex.rs @@ -16,6 +16,8 @@ > >>> use core::cell::UnsafeCell; > >>> use core::marker::PhantomData; > >>>=20 > >>> +pub mod exec; > >>> + > >>> /// Create static [`WwClass`] instances. > >>> /// > >>> /// # Examples > >>> diff --git a/rust/kernel/sync/lock/ww_mutex/exec.rs > >>> b/rust/kernel/sync/lock/ww_mutex/exec.rs new file mode 100644 > >>> index 000000000000..2f1fc540f0b8 > >>> --- /dev/null > >>> +++ b/rust/kernel/sync/lock/ww_mutex/exec.rs > >>> @@ -0,0 +1,176 @@ > >>> +// SPDX-License-Identifier: GPL-2.0 > >>> + > >>> +//! A high-level [`WwMutex`] execution helper. > >>> +//! > >>> +//! Provides a retrying lock mechanism on top of [`WwMutex`] and > >>> [`WwAcquireCtx`]. +//! It detects [`EDEADLK`] and handles it by > >>> rolling back and retrying the +//! user-supplied locking algorithm > >>> until success. + > >>> +use crate::prelude::*; > >>> +use crate::sync::lock::ww_mutex::{WwAcquireCtx, WwClass, WwMutex, > >>> WwMutexGuard}; +use core::ptr; > >>> + > >>> +/// High-level execution type for ww_mutex. > >>> +/// > >>> +/// Tracks a series of locks acquired under a common > >>> [`WwAcquireCtx`]. +/// It ensures proper cleanup and retry > >>> mechanism on deadlocks and provides +/// type-safe access to > >>> locked data via [`with_locked`]. +/// > >>> +/// Typical usage is through [`lock_all`], which retries a > >>> user-supplied +/// locking algorithm until it succeeds without > >>> deadlock. +pub struct ExecContext<'a> { > >>> + class: &'a WwClass, > >>> + acquire: Pin>>, > >>> + taken: KVec>, > >>> +} > >>> + > >>> +impl<'a> Drop for ExecContext<'a> { > >>> + fn drop(&mut self) { > >>> + self.release_all_locks(); > >>=20 > >> If we move this to the acquire context, then we can do away with > >> this drop impl. > >>=20 > >>> + } > >>> +} > >>> + > >>> +impl<'a> ExecContext<'a> { > >>> + /// Creates a new [`ExecContext`] for the given lock class. > >>> + /// > >>> + /// All locks taken through this context must belong to the > >>> same class. > >>> + /// > >>> + /// TODO: Add some safety mechanism to ensure classes are not > >>> different. > >>=20 > >> core::ptr::eq()? > >>=20 > >=20 > > I was thinking more of a type-level mechanism to do ensure that. >=20 > Why? >=20 So that wait-wound and wait-die classes don't get mixed up in the same `ExecContext` by using type validation at compile time. Of course, `core::ptr::eq()` is still useful/required when the classes are of the same type but not exactly the same value. Maybe we can do both. Thanks, Onur