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UPSTREAM: rust: types: add NotThreadSafe

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This introduces a new marker type for types that shouldn't be thread
safe. By adding a field of this type to a struct, it becomes non-Send
and non-Sync, which means that it cannot be accessed in any way from
threads other than the one it was created on.

This is useful for APIs that require globals such as `current` to remain
constant while the value exists.

We update two existing users in the Kernel to use this helper:

 * `Task::current()` - moving the return type of this value to a
   different thread would not be safe as you can no longer be guaranteed
   that the `current` pointer remains valid.
 * Lock guards. Mutexes and spinlocks should be unlocked on the same
   thread as where they were locked, so we enforce this using the Send
   trait.

There are also additional users in later patches of this patchset. See
[1] and [2] for the discussion that led to the introduction of this
patch.

Link: https://lore.kernel.org/all/nFDPJFnzE9Q5cqY7FwSMByRH2OAn_BpI4H53NQfWIlN6I2qfmAqnkp2wRqn0XjMO65OyZY4h6P4K2nAGKJpAOSzksYXaiAK_FoH_8QbgBI4=@proton.me/ [1]
Link: https://lore.kernel.org/all/nFDPJFnzE9Q5cqY7FwSMByRH2OAn_BpI4H53NQfWIlN6I2qfmAqnkp2wRqn0XjMO65OyZY4h6P4K2nAGKJpAOSzksYXaiAK_FoH_8QbgBI4=@proton.me/ [2]
Suggested-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240915-alice-file-v10-1-88484f7a3dcf@google.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

Bug: 370906207
(cherry picked from commit e7572e5deaf3bc36818f19ba35ac8e0c454c8bac)
Change-Id: I5c0a0f9d0479bb375e5d9f35a026355b82ac5d4e
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
This commit is contained in:
Alice Ryhl
2024-09-15 14:31:27 +00:00
parent 69e0d47fbc
commit f58fd7a85d
3 changed files with 36 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files
rust/kernel/sync/lock.rs
+9 -4
View File
@@ -6,8 +6,13 @@
//! spinlocks, raw spinlocks) to be provided with minimal effort.
use super::LockClassKey;
use crate::{init::PinInit, pin_init, str::CStr, types::Opaque, types::ScopeGuard};
use core::{cell::UnsafeCell, marker::PhantomData, marker::PhantomPinned};
use crate::{
init::PinInit,
pin_init,
str::CStr,
types::{NotThreadSafe, Opaque, ScopeGuard},
};
use core::{cell::UnsafeCell, marker::PhantomPinned};
use macros::pin_data;
pub mod mutex;
@@ -139,7 +144,7 @@ impl<T: ?Sized, B: Backend> Lock<T, B> {
pub struct Guard<'a, T: ?Sized, B: Backend> {
pub(crate) lock: &'a Lock<T, B>,
pub(crate) state: B::GuardState,
_not_send: PhantomData<*mut ()>,
_not_send: NotThreadSafe,
}
// SAFETY: `Guard` is sync when the data protected by the lock is also sync.
@@ -191,7 +196,7 @@ impl<'a, T: ?Sized, B: Backend> Guard<'a, T, B> {
Self {
lock,
state,
_not_send: PhantomData,
_not_send: NotThreadSafe,
}
}
}