From nobody Thu Oct 9 20:24:34 2025 Received: from forward206a.mail.yandex.net (forward206a.mail.yandex.net [178.154.239.87]) (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 3CF461D798E for ; Mon, 16 Jun 2025 16:33:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.154.239.87 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750091618; cv=none; b=qZ8IGB5VnZ/8/zdCLiqeILAQgrXofhO8imMI5rJMxzvJz2+eUyRKSpXF6Bf9WQykNr7SPB2tIu2BmmLPM+cKEOsHK3PEAmUePe8hbqf9AtmsQJjTBpswJc46XMPvVVV2l+o4ghHmtlhZGeo7ybvmJq+BXQ9rorWnryUgnhtx5fU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750091618; c=relaxed/simple; bh=u8SnpUvg+OmgTjFeYJWgOlqPSqv/vXFXdNweqOHO+bk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Dg2BpfVKXptStFgzTofcd13d+LPI3dO+X+WBe5sy7T2oe223nfTAbiRRCbbiKz1WqTL+0N3RNfe/xX3GnNzZlVX379sjkDTRE2c6gSmmCm1yQkF5BdVdA1B2D+wkiqrhnQVziGp89RQFGmGI6np2K+HX90A2HfGuZvoJLIRLPKk= 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=UV9flxaD; arc=none smtp.client-ip=178.154.239.87 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="UV9flxaD" Received: from forward100a.mail.yandex.net (forward100a.mail.yandex.net [IPv6:2a02:6b8:c0e:500:1:45:d181:d100]) by forward206a.mail.yandex.net (Yandex) with ESMTPS id 93D226444D for ; Mon, 16 Jun 2025 19:25:38 +0300 (MSK) Received: from mail-nwsmtp-smtp-production-main-64.vla.yp-c.yandex.net (mail-nwsmtp-smtp-production-main-64.vla.yp-c.yandex.net [IPv6:2a02:6b8:c1f:1984:0:640:94c0:0]) by forward100a.mail.yandex.net (Yandex) with ESMTPS id DBF6046D9F; Mon, 16 Jun 2025 19:25:30 +0300 (MSK) Received: by mail-nwsmtp-smtp-production-main-64.vla.yp-c.yandex.net (smtp/Yandex) with ESMTPSA id uOOm811LhiE0-zaJ3MEPh; Mon, 16 Jun 2025 19:25:30 +0300 X-Yandex-Fwd: 1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=onurozkan.dev; s=mail; t=1750091130; bh=OsH5xCf9TMaAzAwlB2Cz47vNBR9kyxuYbvPOtwwINXQ=; h=Message-ID:Date:Cc:Subject:To:From; b=UV9flxaDy7becJ4C3dqdJDxA6BUW8lX0TXcWnd8n0ZxIzQbwG6aH9sUCF4Bh3w3bI 7Yuz8snaY3RUqVzfKhZfiiAvga0XlTVvo2qP6iM+42Q5N+vxAY+n18anuStl1az0yn RwpcPzL3ztbho4xdGRDvZZ0nQyIfmbiekHq0VgO0= Authentication-Results: mail-nwsmtp-smtp-production-main-64.vla.yp-c.yandex.net; dkim=pass header.i=@onurozkan.dev From: onur-ozkan To: linux-kernel@vger.kernel.org Cc: boqun.feng@gmail.com, onur-ozkan , thatslyude@gmail.com Subject: [PATCH] Add `ww_mutex` support & abstraction for Rust tree Date: Mon, 16 Jun 2025 19:24:48 +0300 Message-ID: <20250616162448.31641-1-work@onurozkan.dev> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Adds Rust bindings for the kernel's `ww_mutex` infrastructure to enable deadlock-free acquisition of multiple related locks. The implementation abstracts `ww_mutex.h` header and wraps the existing C `ww_mutex` with three main types: - `WwClass` for grouping related mutexes - `WwAcquireCtx` for tracking lock acquisition context - `WwMutex` for the actual lock Some of the kernel's `ww_mutex` functions are implemented as `static inline= `, so they are inaccessible from Rust as bindgen can't generate code on them. The `rust/helpers/ww_mutex.c file provides C function wrappers around these= inline implementations, so bindgen can see them and generate the corresponding Rus= t code. Link: https://rust-for-linux.zulipchat.com/#narrow/channel/291566-Library/t= opic/Writing.20up.20wrappers.20for.20ww_mutex.3F/with/524269974 Suggested-by: thatslyude@gmail.com Signed-off-by: onur-ozkan --- rust/helpers/helpers.c | 1 + rust/helpers/ww_mutex.c | 39 +++ rust/kernel/error.rs | 1 + rust/kernel/sync/lock.rs | 1 + rust/kernel/sync/lock/ww_mutex.rs | 501 ++++++++++++++++++++++++++++++ 5 files changed, 543 insertions(+) create mode 100644 rust/helpers/ww_mutex.c create mode 100644 rust/kernel/sync/lock/ww_mutex.rs diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index 0f1b5d115985..fd071cbe20a1 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -44,3 +44,4 @@ #include "wait.c" #include "workqueue.c" #include "xarray.c" +#include "ww_mutex.c" diff --git a/rust/helpers/ww_mutex.c b/rust/helpers/ww_mutex.c new file mode 100644 index 000000000000..61a487653394 --- /dev/null +++ b/rust/helpers/ww_mutex.c @@ -0,0 +1,39 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +void rust_helper_ww_mutex_init(struct ww_mutex *lock, struct ww_class *ww_= class) +{ + ww_mutex_init(lock, ww_class); +} + +void rust_helper_ww_acquire_init(struct ww_acquire_ctx *ctx, struct ww_cla= ss *ww_class) +{ + ww_acquire_init(ctx, ww_class); +} + +void rust_helper_ww_acquire_done(struct ww_acquire_ctx *ctx) +{ + ww_acquire_done(ctx); +} + +void rust_helper_ww_acquire_fini(struct ww_acquire_ctx *ctx) +{ + ww_acquire_fini(ctx); +} + +void rust_helper_ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acqui= re_ctx *ctx) +{ + ww_mutex_lock_slow(lock, ctx); +} + +int rust_helper_ww_mutex_lock_slow_interruptible(struct ww_mutex *lock, st= ruct ww_acquire_ctx *ctx) +{ + return ww_mutex_lock_slow_interruptible(lock, ctx); +} + +bool rust_helper_ww_mutex_is_locked(struct ww_mutex *lock) +{ + return ww_mutex_is_locked(lock); +} + diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs index 3dee3139fcd4..94d8014b236b 100644 --- a/rust/kernel/error.rs +++ b/rust/kernel/error.rs @@ -84,6 +84,7 @@ macro_rules! declare_err { declare_err!(EIOCBQUEUED, "iocb queued, will get completion event."); declare_err!(ERECALLCONFLICT, "Conflict with recalled state."); declare_err!(ENOGRACE, "NFS file lock reclaim refused."); + declare_err!(EDEADLK, "Resource deadlock avoided."); } /// Generic integer kernel error. diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs index e82fa5be289c..8824ebc81084 100644 --- a/rust/kernel/sync/lock.rs +++ b/rust/kernel/sync/lock.rs @@ -15,6 +15,7 @@ pub mod mutex; pub mod spinlock; +pub mod ww_mutex; pub(super) mod global; pub use global::{GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedB= y}; diff --git a/rust/kernel/sync/lock/ww_mutex.rs b/rust/kernel/sync/lock/ww_m= utex.rs new file mode 100644 index 000000000000..33de67047420 --- /dev/null +++ b/rust/kernel/sync/lock/ww_mutex.rs @@ -0,0 +1,501 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! A kernel Wound/Wait Mutex. +//! +//! This module provides Rust abstractions for the Linux kernel's `ww_mute= x` implementation, +//! which provides deadlock avoidance through a wait/die algorithm. + +use crate::error::{to_result, Result}; +use crate::prelude::EBUSY; +use crate::{bindings, str::CStr, types::Opaque}; +use core::{cell::UnsafeCell, marker::PhantomPinned, pin::Pin}; +use macros::kunit_tests; +use pin_init::{pin_data, pin_init, pinned_drop, PinInit}; + +/// Implementation of C side `ww_class`. +/// +/// Represents a group of mutexes that can participate in deadlock avoidan= ce together. +/// All mutexes that might be acquired together should use the same class. +/// +/// # Examples +/// +/// ``` +/// use kernel::sync::lock::ww_mutex::WwClass; +/// use kernel::c_str; +/// +/// let _wait_die_class =3D unsafe { WwClass::new(c_str!("graphics_buffers= "), true) }; +/// let _wound_wait_class =3D unsafe { WwClass::new(c_str!("memory_pools")= , false) }; +/// +/// # Ok::<(), Error>(()) +/// ``` +#[repr(transparent)] +pub struct WwClass(Opaque); + +// SAFETY: `WwClass` can be shared between threads. +unsafe impl Sync for WwClass {} + +impl WwClass { + /// Creates `WwClass` that wraps C side `ww_class`. + /// + /// # Safety + /// + /// The caller must ensure that the returned `WwClass` is not moved or= freed + /// while any `WwMutex` instances using this class exist. + pub unsafe fn new(name: &'static CStr, is_wait_die: bool) -> Self { + Self(Opaque::new(bindings::ww_class { + stamp: bindings::atomic_long_t { counter: 0 }, + acquire_name: name.as_char_ptr(), + mutex_name: name.as_char_ptr(), + is_wait_die: is_wait_die as u32, + + // `lock_class_key` doesn't have any value + acquire_key: bindings::lock_class_key {}, + mutex_key: bindings::lock_class_key {}, + })) + } +} + +/// Implementation of C side `ww_acquire_ctx`. +/// +/// An acquire context is used to group multiple mutex acquisitions togeth= er +/// for deadlock avoidance. It must be used when acquiring multiple mutexes +/// of the same class. +/// +/// # Examples +/// +/// ``` +/// use kernel::sync::lock::ww_mutex::{WwClass, WwAcquireCtx, WwMutex}; +/// use kernel::alloc::KBox; +/// use kernel::c_str; +/// +/// let class =3D unsafe { WwClass::new(c_str!("my_class"), false) }; +/// +/// // Create mutexes +/// let mutex1 =3D unsafe { KBox::pin_init(WwMutex::new(1u32, &class), GFP= _KERNEL).unwrap() }; +/// let mutex2 =3D unsafe { KBox::pin_init(WwMutex::new(2u32, &class), GFP= _KERNEL).unwrap() }; +/// +/// // Create acquire context for deadlock avoidance +/// let mut ctx =3D KBox::pin_init( +/// unsafe { WwAcquireCtx::new(&class) }, +/// GFP_KERNEL +/// ).unwrap(); +/// +/// // Acquire multiple locks safely +/// let guard1 =3D mutex1.as_ref().lock(Some(&ctx)).unwrap(); +/// let guard2 =3D mutex2.as_ref().lock(Some(&ctx)).unwrap(); +/// +/// // Mark acquisition phase as complete +/// ctx.as_mut().done(); +/// +/// # Ok::<(), Error>(()) +/// ``` +#[pin_data(PinnedDrop)] +pub struct WwAcquireCtx { + #[pin] + inner: Opaque, + #[pin] + _pin: PhantomPinned, +} + +// SAFETY: `WwAcquireCtx` is safe to send between threads when not in use. +unsafe impl Send for WwAcquireCtx {} + +impl WwAcquireCtx { + /// Initializes `Self` with calling C side `ww_acquire_init` inside. + /// + /// # Safety + /// + /// The caller must ensure that the `ww_class` remains valid for the l= ifetime + /// of this context. + pub unsafe fn new(ww_class: &WwClass) -> impl PinInit { + let raw_ptr =3D ww_class.0.get(); + + pin_init!(WwAcquireCtx { + inner <- Opaque::ffi_init(|slot: *mut bindings::ww_acquire_ctx= | { + // SAFETY: The caller guarantees that `ww_class` remains v= alid. + unsafe { + bindings::ww_acquire_init(slot, raw_ptr) + } + }), + _pin: PhantomPinned, + }) + } + + /// Marks the end of the acquire phase with C side `ww_acquire_done`. + /// + /// After calling this function, no more mutexes can be acquired with = this context. + pub fn done(self: Pin<&mut Self>) { + // SAFETY: The context is pinned and valid. + unsafe { + bindings::ww_acquire_done(self.inner.get()); + } + } + + /// Returns a raw pointer to the inner `ww_acquire_ctx`. + /// + /// # Safety + /// + /// The caller must ensure proper synchronization when using the raw p= ointer. + unsafe fn as_ptr(&self) -> *mut bindings::ww_acquire_ctx { + self.inner.get() + } +} + +#[pinned_drop] +impl PinnedDrop for WwAcquireCtx { + fn drop(self: Pin<&mut Self>) { + // SAFETY: The context is being dropped and is pinned. + unsafe { + bindings::ww_acquire_fini(self.inner.get()); + } + } +} + +/// A wound/wait mutex backed with C side `ww_mutex`. +/// +/// This is a mutual exclusion primitive that provides deadlock avoidance = when +/// acquiring multiple locks of the same class. +/// +/// # Examples +/// +/// ## Basic Usage +/// +/// ``` +/// use kernel::sync::lock::ww_mutex::{WwClass, WwMutex}; +/// use kernel::alloc::KBox; +/// use kernel::c_str; +/// +/// let class =3D unsafe { WwClass::new(c_str!("buffer_class"), false) }; +/// let mutex =3D unsafe { KBox::pin_init(WwMutex::new(42u32, &class), GFP= _KERNEL).unwrap() }; +/// +/// // Simple lock without context +/// let guard =3D mutex.as_ref().lock(None).unwrap(); +/// assert_eq!(*guard, 42); +/// +/// # Ok::<(), Error>(()) +/// ``` +/// +/// ## Multiple Lock Acquisition with Deadlock Avoidance +/// +/// ``` +/// use kernel::sync::lock::ww_mutex::{WwClass, WwAcquireCtx, WwMutex}; +/// use kernel::alloc::KBox; +/// use kernel::c_str; +/// use kernel::error::code::*; +/// +/// let class =3D unsafe { WwClass::new(c_str!("resource_class"), true) }; +/// let mutex_a =3D unsafe { KBox::pin_init(WwMutex::new("Resource A", &cl= ass), GFP_KERNEL).unwrap() }; +/// let mutex_b =3D unsafe { KBox::pin_init(WwMutex::new("Resource B", &cl= ass), GFP_KERNEL).unwrap() }; +/// +/// let mut ctx =3D KBox::pin_init(unsafe { WwAcquireCtx::new(&class) }, G= FP_KERNEL).unwrap(); +/// +/// // Try to acquire both locks +/// let guard_a =3D match mutex_a.as_ref().lock(Some(&ctx)) { +/// Ok(guard) =3D> guard, +/// Err(e) if e =3D=3D EDEADLK =3D> { +/// // Deadlock detected, use slow path +/// mutex_a.as_ref().lock_slow(&ctx).unwrap() +/// } +/// Err(e) =3D> return Err(e), +/// }; +/// +/// let guard_b =3D mutex_b.as_ref().lock(Some(&ctx)).unwrap(); +/// ctx.as_mut().done(); +/// +/// # Ok::<(), Error>(()) +/// ``` +#[pin_data] +pub struct WwMutex { + #[pin] + mutex: Opaque, + #[pin] + data: UnsafeCell, +} + +// SAFETY: `WwMutex` can be transferred across thread boundaries. +unsafe impl Send for WwMutex {} + +// SAFETY: `WwMutex` can be shared between threads. +unsafe impl Sync for WwMutex {} + +impl WwMutex { + /// Creates `Self` with calling `ww_mutex_init` inside. + /// + /// # Safety + /// + /// The caller must ensure that the `WwClass` remains valid for the li= fetime + /// of this mutex. + pub unsafe fn new(t: T, ww_class: &WwClass) -> impl PinInit { + let raw_ptr =3D ww_class.0.get(); + pin_init!(WwMutex { + mutex <- Opaque::ffi_init(|slot: *mut bindings::ww_mutex| { + // SAFETY: The caller guarantees that `ww_class` remains v= alid. + unsafe { + bindings::ww_mutex_init(slot, raw_ptr) + } + }), + data: UnsafeCell::new(t), + }) + } +} + +impl WwMutex { + /// Locks the mutex with the given acquire context. + pub fn lock<'a>( + self: Pin<&'a Self>, + ctx: Option<&WwAcquireCtx>, + ) -> Result> { + // SAFETY: The mutex is pinned and valid. + let ret =3D unsafe { + bindings::ww_mutex_lock( + self.mutex.get(), + ctx.map_or(core::ptr::null_mut(), |c| c.as_ptr()), + ) + }; + + to_result(ret)?; + + // SAFETY: We just acquired the lock. + Ok(unsafe { WwMutexGuard::new(self) }) + } + + /// Locks the mutex with the given acquire context, interruptible. + /// + /// Similar to `lock`, but can be interrupted by signals. + pub fn lock_interruptible<'a>( + self: Pin<&'a Self>, + ctx: Option<&WwAcquireCtx>, + ) -> Result> { + // SAFETY: The mutex is pinned and valid. + let ret =3D unsafe { + bindings::ww_mutex_lock_interruptible( + self.mutex.get(), + ctx.map_or(core::ptr::null_mut(), |c| c.as_ptr()), + ) + }; + + to_result(ret)?; + + // SAFETY: We just acquired the lock. + Ok(unsafe { WwMutexGuard::new(self) }) + } + + /// Locks the mutex in the slow path after a die case. + /// + /// This should be called after releasing all held mutexes when `lock`= returns `EDEADLK`. + pub fn lock_slow<'a>(self: Pin<&'a Self>, ctx: &WwAcquireCtx) -> Resul= t> { + // SAFETY: The mutex is pinned and valid, and we're in the slow pa= th. + unsafe { + bindings::ww_mutex_lock_slow(self.mutex.get(), ctx.as_ptr()); + } + + // SAFETY: We just acquired the lock. + Ok(unsafe { WwMutexGuard::new(self) }) + } + + /// Locks the mutex in the slow path after a die case, interruptible. + pub fn lock_slow_interruptible<'a>( + self: Pin<&'a Self>, + ctx: &WwAcquireCtx, + ) -> Result> { + // SAFETY: The mutex is pinned and valid, and we are in the slow p= ath. + let ret =3D + unsafe { bindings::ww_mutex_lock_slow_interruptible(self.mutex= .get(), ctx.as_ptr()) }; + + to_result(ret)?; + + // SAFETY: We just acquired the lock. + Ok(unsafe { WwMutexGuard::new(self) }) + } + + /// Tries to lock the mutex without blocking. + pub fn try_lock<'a>( + self: Pin<&'a Self>, + ctx: Option<&WwAcquireCtx>, + ) -> Result> { + // SAFETY: The mutex is pinned and valid. + let ret =3D unsafe { + bindings::ww_mutex_trylock( + self.mutex.get(), + ctx.map_or(core::ptr::null_mut(), |c| c.as_ptr()), + ) + }; + + if ret =3D=3D 0 { + return Err(EBUSY); + } + + to_result(if ret < 0 { ret } else { 0 })?; + + // SAFETY: We just acquired the lock. + Ok(unsafe { WwMutexGuard::new(self) }) + } + + /// Checks if the mutex is currently locked. + pub fn is_locked(self: Pin<&Self>) -> bool { + // SAFETY: The mutex is pinned and valid. + unsafe { bindings::ww_mutex_is_locked(self.mutex.get()) } + } + + /// Returns a raw pointer to the inner mutex. + /// + /// # Safety + /// + /// The caller must ensure proper synchronization when using the raw p= ointer. + unsafe fn as_ptr(&self) -> *mut bindings::ww_mutex { + self.mutex.get() + } +} + +/// A guard that provides exclusive access to the data protected by a +// [`WwMutex`] (a.k.a `ww_mutex` on the C side). +pub struct WwMutexGuard<'a, T: ?Sized> { + mutex: Pin<&'a WwMutex>, +} + +// SAFETY: `WwMutexGuard` can be transferred across thread boundaries if t= he data can. +unsafe impl Send for WwMutexGuard<'_, T> {} + +// SAFETY: `WwMutexGuard` can be shared between threads if the data can. +unsafe impl Sync for WwMutexGuard<'_, T> {} + +impl<'a, T: ?Sized> WwMutexGuard<'a, T> { + /// Creates a new guard for a locked mutex. + /// + /// # Safety + /// + /// The caller must ensure that the mutex is actually locked. + unsafe fn new(mutex: Pin<&'a WwMutex>) -> Self { + Self { mutex } + } +} + +impl core::ops::Deref for WwMutexGuard<'_, T> { + type Target =3D T; + + fn deref(&self) -> &Self::Target { + // SAFETY: We hold the lock, so we have exclusive access. + unsafe { &*self.mutex.data.get() } + } +} + +impl core::ops::DerefMut for WwMutexGuard<'_, T> { + fn deref_mut(&mut self) -> &mut Self::Target { + // SAFETY: We hold the lock, so we have exclusive access. + unsafe { &mut *self.mutex.data.get() } + } +} + +impl Drop for WwMutexGuard<'_, T> { + fn drop(&mut self) { + // SAFETY: We hold the lock and are about to release it. + unsafe { + bindings::ww_mutex_unlock(self.mutex.as_ptr()); + } + } +} + +#[kunit_tests(rust_kernel_ww_mutex)] +mod tests { + use crate::alloc::KBox; + use crate::c_str; + use crate::init::InPlaceInit; + use crate::prelude::*; + + use super::*; + + #[test] + fn test_ww_mutex_basic_lock_unlock() { + // SAFETY: valid for this test, nothing to worry about + + let class =3D unsafe { WwClass::new(c_str!("test_mutex_class"), fa= lse) }; + + // SAFETY: valid for this test, nothing to worry about + + let mutex =3D unsafe { KBox::pin_init(WwMutex::new(42, &class), GF= P_KERNEL).unwrap() }; + + // Lock without context + let guard =3D mutex.as_ref().lock(None).unwrap(); + assert_eq!(*guard, 42); + + // Drop the lock + drop(guard); + + // Lock it again + let mut guard =3D mutex.as_ref().lock(None).unwrap(); + *guard =3D 100; + assert_eq!(*guard, 100); + } + + #[test] + fn test_ww_mutex_trylock() { + // SAFETY: valid for this test, nothing to worry about + + let class =3D unsafe { WwClass::new(c_str!("trylock_class"), false= ) }; + // SAFETY: valid for this test, nothing to worry about + + let mutex =3D unsafe { KBox::pin_init(WwMutex::new(123i32, &class)= , GFP_KERNEL).unwrap() }; + + // trylock on unlocked mutex should succeed + let guard =3D mutex.as_ref().try_lock(None).unwrap(); + assert_eq!(*guard, 123); + drop(guard); + + // lock it first + let _guard1 =3D mutex.as_ref().lock(None).unwrap(); + + // trylock should fail with EBUSY when already locked + let result =3D mutex.as_ref().try_lock(None); + match result { + Err(e) =3D> assert_eq!(e, EBUSY), + Ok(_) =3D> panic!("Expected `EBUSY` but got success"), + } + } + + #[test] + fn test_ww_mutex_is_locked() { + // SAFETY: valid for this test, nothing to worry about + + let class =3D unsafe { WwClass::new(c_str!("locked_check_class"), = true) }; + // SAFETY: valid for this test, nothing to worry about + + let mutex =3D unsafe { KBox::pin_init(WwMutex::new("hello", &class= ), GFP_KERNEL).unwrap() }; + + // should not be locked initially + assert!(!mutex.as_ref().is_locked()); + + let guard =3D mutex.as_ref().lock(None).unwrap(); + assert!(mutex.as_ref().is_locked()); + + drop(guard); + assert!(!mutex.as_ref().is_locked()); + } + + #[test] + fn test_ww_acquire_context() { + // SAFETY: valid for this test, nothing to worry about + let class =3D unsafe { WwClass::new(c_str!("ctx_class"), false) }; + + // SAFETY: valid for this test, nothing to worry about + let mutex1 =3D unsafe { KBox::pin_init(WwMutex::new(1u64, &class),= GFP_KERNEL).unwrap() }; + + // SAFETY: valid for this test, nothing to worry about + let mutex2 =3D unsafe { KBox::pin_init(WwMutex::new(2u64, &class),= GFP_KERNEL).unwrap() }; + + // SAFETY: valid for this test, nothing to worry about + let mut ctx =3D unsafe { KBox::pin_init(WwAcquireCtx::new(&class),= GFP_KERNEL).unwrap() }; + + // acquire multiple mutexes with same context + let guard1 =3D mutex1.as_ref().lock(Some(&ctx)).unwrap(); + let guard2 =3D mutex2.as_ref().lock(Some(&ctx)).unwrap(); + + assert_eq!(*guard1, 1); + assert_eq!(*guard2, 2); + + ctx.as_mut().done(); + + // we shouldn't be able to lock once it's `done`. + assert!(mutex1.as_ref().lock(Some(&ctx)).is_err()); + assert!(mutex2.as_ref().lock(Some(&ctx)).is_err()); + } +} 2.49.0