From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 38A6C189B9C; Thu, 2 Jan 2025 09:44:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735811070; cv=none; b=jp5V42ks9gt2x86bJkBtpCJLYeGrOB4IIFKgXeHyUFDCbP7vUh8++fzIZs7vpC5YyVxVHJZ/ysiMYrgNsiIMeB6pZPeVqhXqoAnMH7+vsuFn6dHfIb9DCF6KkPmzAEVR0PpNFXToS/4u7FpRxKaRCSxCW1wVMF3lQCTBATNU+d8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735811070; c=relaxed/simple; bh=hxWnEH8xQveHUbVj8BZY+CdgkxEOLd5OTlXgJppqR7Q=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OYM44G7WD/j+bX7mjBi0hc1VEi2j6nhBSAL9N+fBep4OmQP3RPR2PPJdVk6hpuSFc4L0u2Q7s5oxfwAmIoxlfKkVQZymaGH25salf8dehlKup9bKAIKFqJGMkBO4oE2aQ/ALLItQ0Jh3Go6IQjOfT7JrtdmxrUq7LfBemkziTok= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gR1z6jgF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gR1z6jgF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7CE6DC4CED0; Thu, 2 Jan 2025 09:44:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1735811069; bh=hxWnEH8xQveHUbVj8BZY+CdgkxEOLd5OTlXgJppqR7Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gR1z6jgFgINsIIYD7esGa3SE+na7oPd0HtMUE98YZoBB92vgXKi40zzlhSQFafsGg g3Rrav7XwkA+GHZpWH27U7SdcFyN2/gaSSv0aeMhoxmtnQwRPrTmpA0yvxD/q7eHxO 14tlaMSxO1T+cpZGHc+wcaea3n9wb5BMN5z+5WDdGjSSDytY+2JMVA1BpcmpYdO9am Km5bgbINI2JIm/41AxTgb253oa6xWt2RTuxOnBPGqEs/PbrGY72XIn8LchtTEoTXTS fhixUtZhhPdECxp8GIeSPqqJnObAAbwOhIJu38IqfVkZahyfTC/x2T7hkO/OSa/F9x mp6wcwcZ2pD7Q== Date: Thu, 2 Jan 2025 10:44:20 +0100 From: Danilo Krummrich To: Gary Guo Cc: gregkh@linuxfoundation.org, rafael@kernel.org, bhelgaas@google.com, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, bjorn3_gh@protonmail.com, benno.lossin@proton.me, tmgross@umich.edu, a.hindborg@samsung.com, aliceryhl@google.com, airlied@gmail.com, fujita.tomonori@gmail.com, lina@asahilina.net, pstanner@redhat.com, ajanulgu@redhat.com, lyude@redhat.com, robh@kernel.org, daniel.almeida@collabora.com, saravanak@google.com, dirk.behme@de.bosch.com, j@jannau.net, fabien.parent@linaro.org, chrisi.schrefl@gmail.com, paulmck@kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, devicetree@vger.kernel.org, rcu@vger.kernel.org, Wedson Almeida Filho Subject: Re: [PATCH v7 04/16] rust: add rcu abstraction Message-ID: References: <20241219170425.12036-1-dakr@kernel.org> <20241219170425.12036-5-dakr@kernel.org> <20241224205450.20171869.gary@garyguo.net> 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=us-ascii Content-Disposition: inline In-Reply-To: <20241224205450.20171869.gary@garyguo.net> On Tue, Dec 24, 2024 at 08:54:50PM +0000, Gary Guo wrote: > On Thu, 19 Dec 2024 18:04:06 +0100 > Danilo Krummrich wrote: > > > From: Wedson Almeida Filho > > > > Add a simple abstraction to guard critical code sections with an rcu > > read lock. > > > > Reviewed-by: Boqun Feng > > Signed-off-by: Wedson Almeida Filho > > Co-developed-by: Danilo Krummrich > > Signed-off-by: Danilo Krummrich > > --- > > MAINTAINERS | 1 + > > rust/helpers/helpers.c | 1 + > > rust/helpers/rcu.c | 13 ++++++++++++ > > rust/kernel/sync.rs | 1 + > > rust/kernel/sync/rcu.rs | 47 +++++++++++++++++++++++++++++++++++++++++ > > 5 files changed, 63 insertions(+) > > create mode 100644 rust/helpers/rcu.c > > create mode 100644 rust/kernel/sync/rcu.rs > > [resend to the list] > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index 3cfb68650347..0cc69e282889 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -19690,6 +19690,7 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev > > F: Documentation/RCU/ > > F: include/linux/rcu* > > F: kernel/rcu/ > > +F: rust/kernel/sync/rcu.rs > > X: Documentation/RCU/torture.rst > > X: include/linux/srcu*.h > > X: kernel/rcu/srcu*.c > > diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c > > index dcf827a61b52..060750af6524 100644 > > --- a/rust/helpers/helpers.c > > +++ b/rust/helpers/helpers.c > > @@ -20,6 +20,7 @@ > > #include "page.c" > > #include "pid_namespace.c" > > #include "rbtree.c" > > +#include "rcu.c" > > #include "refcount.c" > > #include "security.c" > > #include "signal.c" > > diff --git a/rust/helpers/rcu.c b/rust/helpers/rcu.c > > new file mode 100644 > > index 000000000000..f1cec6583513 > > --- /dev/null > > +++ b/rust/helpers/rcu.c > > @@ -0,0 +1,13 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > + > > +#include > > + > > +void rust_helper_rcu_read_lock(void) > > +{ > > + rcu_read_lock(); > > +} > > + > > +void rust_helper_rcu_read_unlock(void) > > +{ > > + rcu_read_unlock(); > > +} > > diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs > > index 1eab7ebf25fd..0654008198b2 100644 > > --- a/rust/kernel/sync.rs > > +++ b/rust/kernel/sync.rs > > @@ -12,6 +12,7 @@ > > pub mod lock; > > mod locked_by; > > pub mod poll; > > +pub mod rcu; > > > > pub use arc::{Arc, ArcBorrow, UniqueArc}; > > pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult}; > > diff --git a/rust/kernel/sync/rcu.rs b/rust/kernel/sync/rcu.rs > > new file mode 100644 > > index 000000000000..b51d9150ffe2 > > --- /dev/null > > +++ b/rust/kernel/sync/rcu.rs > > @@ -0,0 +1,47 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > + > > +//! RCU support. > > +//! > > +//! C header: [`include/linux/rcupdate.h`](srctree/include/linux/rcupdate.h) > > + > > +use crate::{bindings, types::NotThreadSafe}; > > + > > +/// Evidence that the RCU read side lock is held on the current thread/CPU. > > +/// > > +/// The type is explicitly not `Send` because this property is per-thread/CPU. > > +/// > > +/// # Invariants > > +/// > > +/// The RCU read side lock is actually held while instances of this guard exist. > > +pub struct Guard(NotThreadSafe); > > + > > +impl Guard { > > + /// Acquires the RCU read side lock and returns a guard. > > + pub fn new() -> Self { > > + // SAFETY: An FFI call with no additional requirements. > > + unsafe { bindings::rcu_read_lock() }; > > + // INVARIANT: The RCU read side lock was just acquired above. > > + Self(NotThreadSafe) > > + } > > + > > + /// Explicitly releases the RCU read side lock. > > + pub fn unlock(self) {} > > I don't think there's need for this, `drop(rcu_guard)` is equally > clear. I don't mind one or the other, feel free to send a patch to remove it. :) > > There was a debate in Rust community about explicit lock methods, but > the conclusion was to not have it, > see https://github.com/rust-lang/rust/issues/81872. > > > +} > > + > > +impl Default for Guard { > > + fn default() -> Self { > > + Self::new() > > + } > > +} > > I don't think anyone would like to implicit acquire an RCU guard! I > believe you included this because clippy is yelling, but in this case > you shouldn't listen to clippy. Either suppress the warning or rename > `new` to `lock`. I picked up this patch from Wedson, so I can't tell for sure. I don't see any other reason for this though, so we could remove it. > > > + > > +impl Drop for Guard { > > + fn drop(&mut self) { > > + // SAFETY: By the type invariants, the RCU read side is locked, so it is ok to unlock it. > > + unsafe { bindings::rcu_read_unlock() }; > > + } > > +} > > + > > +/// Acquires the RCU read side lock. > > +pub fn read_lock() -> Guard { > > + Guard::new() > > +} >