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[2003:df:bf03:a200:eeb1:4cf6:acf1:a130]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-abf75481eb4sm94031366b.83.2025.03.02.09.07.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 02 Mar 2025 09:07:44 -0800 (PST) Message-ID: <7026deb6-6e35-47f6-9462-0880a5b47509@gmail.com> Date: Sun, 2 Mar 2025 18:07:43 +0100 Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 6/9] rust: sync: Add SpinLockIrq To: Lyude Paul , rust-for-linux@vger.kernel.org, Thomas Gleixner Cc: Boqun Feng , Miguel Ojeda , Alex Gaynor , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Wedson Almeida Filho , open list References: <20250227221924.265259-1-lyude@redhat.com> <20250227221924.265259-7-lyude@redhat.com> Content-Language: en-US From: Dirk Behme In-Reply-To: <20250227221924.265259-7-lyude@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 27.02.25 23:10, Lyude Paul wrote: > A variant of SpinLock that is expected to be used in noirq contexts, so > lock() will disable interrupts and unlock() (i.e. `Guard::drop()` will > undo the interrupt disable. > > [Boqun: Port to use spin_lock_irq_disable() and > spin_unlock_irq_enable()] > > Signed-off-by: Lyude Paul > Co-Developed-by: Boqun Feng > Signed-off-by: Boqun Feng > --- > rust/kernel/sync.rs | 4 +- > rust/kernel/sync/lock/spinlock.rs | 141 ++++++++++++++++++++++++++++++ > 2 files changed, 144 insertions(+), 1 deletion(-) > ... > diff --git a/rust/kernel/sync/lock/spinlock.rs b/rust/kernel/sync/lock/spinlock.rs > index ab2f8d0753116..ac66493f681ce 100644 > --- a/rust/kernel/sync/lock/spinlock.rs > +++ b/rust/kernel/sync/lock/spinlock.rs > @@ -139,3 +139,144 @@ unsafe fn assert_is_held(ptr: *mut Self::State) { > unsafe { bindings::spin_assert_is_held(ptr) } > } > } > + > +/// Creates a [`SpinLockIrq`] initialiser with the given name and a newly-created lock class. > +/// > +/// It uses the name if one is given, otherwise it generates one based on the file name and line > +/// number. > +#[macro_export] > +macro_rules! new_spinlock_irq { > + ($inner:expr $(, $name:literal)? $(,)?) => { > + $crate::sync::SpinLockIrq::new( > + $inner, $crate::optional_name!($($name)?), $crate::static_lock_class!()) > + }; > +} > +pub use new_spinlock_irq; > + > +/// A spinlock that may be acquired when local processor interrupts are disabled. > +/// > +/// This is a version of [`SpinLock`] that can only be used in contexts where interrupts for the > +/// local CPU are disabled. It can be acquired in two ways: > +/// > +/// - Using [`lock()`] like any other type of lock, in which case the bindings will ensure that > +/// interrupts remain disabled for at least as long as the [`SpinLockIrqGuard`] exists. The [`lock_with()`] below states "interrupt state will not be touched". Should the [`lock()`] part above mention that the interrupt state *is* touched, then? Like in the comment in the example below ("... e.c.lock(); // interrupts are disabled now")? For example: ... the bindings will ensure that interrupts are disabled and remain disabled ... ? Dirk > +/// - Using [`lock_with()`] in contexts where a [`LocalInterruptDisabled`] token is present and > +/// local processor interrupts are already known to be disabled, in which case the local interrupt > +/// state will not be touched. This method should be preferred if a [`LocalInterruptDisabled`] > +/// token is present in the scope. > +/// > +/// For more info on spinlocks, see [`SpinLock`]. For more information on interrupts, > +/// [see the interrupt module](kernel::interrupt). > +/// > +/// # Examples > +/// > +/// The following example shows how to declare, allocate initialise and access a struct (`Example`) > +/// that contains an inner struct (`Inner`) that is protected by a spinlock that requires local > +/// processor interrupts to be disabled. > +/// > +/// ``` > +/// use kernel::sync::{new_spinlock_irq, SpinLockIrq}; > +/// > +/// struct Inner { > +/// a: u32, > +/// b: u32, > +/// } > +/// > +/// #[pin_data] > +/// struct Example { > +/// #[pin] > +/// c: SpinLockIrq, > +/// #[pin] > +/// d: SpinLockIrq, > +/// } > +/// > +/// impl Example { > +/// fn new() -> impl PinInit { > +/// pin_init!(Self { > +/// c <- new_spinlock_irq!(Inner { a: 0, b: 10 }), > +/// d <- new_spinlock_irq!(Inner { a: 20, b: 30 }), > +/// }) > +/// } > +/// } > +/// > +/// // Allocate a boxed `Example` > +/// let e = KBox::pin_init(Example::new(), GFP_KERNEL)?; > +/// > +/// // Accessing an `Example` from a context where interrupts may not be disabled already. > +/// let c_guard = e.c.lock(); // interrupts are disabled now, +1 interrupt disable refcount > +/// let d_guard = e.d.lock(); // no interrupt state change, +1 interrupt disable refcount > +/// > +/// assert_eq!(c_guard.a, 0); > +/// assert_eq!(c_guard.b, 10); > +/// assert_eq!(d_guard.a, 20); > +/// assert_eq!(d_guard.b, 30); > +/// > +/// drop(c_guard); // Dropping c_guard will not re-enable interrupts just yet, since d_guard is > +/// // still in scope. > +/// drop(d_guard); // Last interrupt disable reference dropped here, so interrupts are re-enabled > +/// // now > +/// # Ok::<(), Error>(()) > +/// ``` > +/// > +/// [`lock()`]: SpinLockIrq::lock > +/// [`lock_with()`]: SpinLockIrq::lock_with > +pub type SpinLockIrq = super::Lock;