Message-Id: <20230714-classless_lockdep-v1-8-229b9671ce31@asahilina.net>
Date:   Fri, 14 Jul 2023 18:14:00 +0900
From:   Asahi Lina <lina@...hilina.net>
To:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Benno Lossin <benno.lossin@...ton.me>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>, Tom Rix <trix@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        asahi@...ts.linux.dev, rust-for-linux@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        llvm@...ts.linux.dev, Asahi Lina <lina@...hilina.net>
Subject: [PATCH RFC 08/11] rust: sync: Classless Lock::new() and pin_init()

Use the new automagic lock class code to remove the lock class and name
parameters from Lock::new() and Lock::pin_init(). The old functions
are renamed to new_with_class() and pin_init_with_class() respectively.

The new approach uses the caller tracking machinery in Rust, which means
it can be trivially wrapped by adding #[track_caller] to any functions
that should bubble up lock class creation to their caller. This, for
example, allows a type using multiple Mutexes to create separate lock
classes for every user of the type, simply by adding that attribute to
the mutex creation code paths.

Signed-off-by: Asahi Lina <lina@...hilina.net>
---
 rust/kernel/sync/lock.rs          | 42 +++++++++++++++++++++++++++++++++++----
 rust/kernel/sync/lock/mutex.rs    |  4 ++--
 rust/kernel/sync/lock/spinlock.rs |  2 +-
 3 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
index 8e71e7aa2cc1..8849741c1d9a 100644
--- a/rust/kernel/sync/lock.rs
+++ b/rust/kernel/sync/lock.rs
@@ -5,7 +5,7 @@
 //! It contains a generic Rust lock and guard that allow for different backends (e.g., mutexes,
 //! spinlocks, raw spinlocks) to be provided with minimal effort.
 
-use super::LockClassKey;
+use super::{lockdep::caller_lock_class, LockClassKey};
 use crate::{
     bindings, init::PinInit, pin_init, str::CStr, try_pin_init, types::Opaque, types::ScopeGuard,
 };
@@ -103,7 +103,40 @@ unsafe impl<T: ?Sized + Send, B: Backend> Sync for Lock<T, B> {}
 impl<T, B: Backend> Lock<T, B> {
     /// Constructs a new lock initialiser.
     #[allow(clippy::new_ret_no_self)]
-    pub fn new(t: T, name: &'static CStr, key: LockClassKey) -> impl PinInit<Self> {
+    #[track_caller]
+    pub fn new(t: T) -> impl PinInit<Self> {
+        let (key, name) = caller_lock_class();
+        Self::new_with_key(t, name, key)
+    }
+
+    /// Constructs a new lock initialiser taking an initialiser/
+    pub fn pin_init<E>(t: impl PinInit<T, E>) -> impl PinInit<Self, E>
+    where
+        E: core::convert::From<core::convert::Infallible>,
+    {
+        let (key, name) = caller_lock_class();
+        Self::pin_init_with_key(t, name, key)
+    }
+
+    /// Constructs a new lock initialiser.
+    #[allow(clippy::new_ret_no_self)]
+    #[track_caller]
+    pub fn new_named(t: T, name: &'static CStr) -> impl PinInit<Self> {
+        let (key, _) = caller_lock_class();
+        Self::new_with_key(t, name, key)
+    }
+
+    /// Constructs a new lock initialiser taking an initialiser/
+    pub fn pin_init_named<E>(t: impl PinInit<T, E>, name: &'static CStr) -> impl PinInit<Self, E>
+    where
+        E: core::convert::From<core::convert::Infallible>,
+    {
+        let (key, _) = caller_lock_class();
+        Self::pin_init_with_key(t, name, key)
+    }
+
+    /// Constructs a new lock initialiser given a particular name and lock class key.
+    pub fn new_with_key(t: T, name: &'static CStr, key: LockClassKey) -> impl PinInit<Self> {
         pin_init!(Self {
             data: UnsafeCell::new(t),
             _pin: PhantomPinned,
@@ -115,8 +148,9 @@ pub fn new(t: T, name: &'static CStr, key: LockClassKey) -> impl PinInit<Self> {
         })
     }
 
-    /// Constructs a new lock initialiser taking an initialiser.
-    pub fn pin_init<E>(
+    /// Constructs a new lock initialiser taking an initialiser given a particular
+    /// name and lock class key.
+    pub fn pin_init_with_key<E>(
         t: impl PinInit<T, E>,
         name: &'static CStr,
         key: LockClassKey,
diff --git a/rust/kernel/sync/lock/mutex.rs b/rust/kernel/sync/lock/mutex.rs
index 06fe685501b4..15ea70fa3933 100644
--- a/rust/kernel/sync/lock/mutex.rs
+++ b/rust/kernel/sync/lock/mutex.rs
@@ -13,7 +13,7 @@
 #[macro_export]
 macro_rules! new_mutex {
     ($inner:expr $(, $name:literal)? $(,)?) => {
-        $crate::sync::Mutex::new(
+        $crate::sync::Mutex::new_with_key(
             $inner, $crate::optional_name!($($name)?), $crate::static_lock_class!())
     };
 }
@@ -26,7 +26,7 @@ macro_rules! new_mutex {
 #[macro_export]
 macro_rules! new_mutex_pinned {
     ($inner:expr $(, $name:literal)? $(,)?) => {
-        $crate::sync::Mutex::pin_init(
+        $crate::sync::Mutex::pin_init_with_key(
             $inner, $crate::optional_name!($($name)?), $crate::static_lock_class!())
     };
 }
diff --git a/rust/kernel/sync/lock/spinlock.rs b/rust/kernel/sync/lock/spinlock.rs
index 979b56464a4e..9f6137f047ee 100644
--- a/rust/kernel/sync/lock/spinlock.rs
+++ b/rust/kernel/sync/lock/spinlock.rs
@@ -13,7 +13,7 @@
 #[macro_export]
 macro_rules! new_spinlock {
     ($inner:expr $(, $name:literal)? $(,)?) => {
-        $crate::sync::SpinLock::new(
+        $crate::sync::SpinLock::new_with_class(
             $inner, $crate::optional_name!($($name)?), $crate::static_lock_class!())
     };
 }

-- 
2.40.1

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