rust/kernel/task.rs - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0

 //! Tasks (threads and processes).
 //!
 //! C header: [`include/linux/sched.h`](srctree/include/linux/sched.h).

 use crate::{
     bindings,
     ffi::{c_int, c_long, c_uint},
     mm::MmWithUser,
     pid_namespace::PidNamespace,
     types::{ARef, NotThreadSafe, Opaque},
 };
 use core::{
     cmp::{Eq, PartialEq},
     ops::Deref,
     ptr,
 };

 /// A sentinel value used for infinite timeouts.
 pub const MAX_SCHEDULE_TIMEOUT: c_long = c_long::MAX;

 /// Bitmask for tasks that are sleeping in an interruptible state.
 pub const TASK_INTERRUPTIBLE: c_int = bindings::TASK_INTERRUPTIBLE as c_int;
 /// Bitmask for tasks that are sleeping in an uninterruptible state.
 pub const TASK_UNINTERRUPTIBLE: c_int = bindings::TASK_UNINTERRUPTIBLE as c_int;
 /// Bitmask for tasks that are sleeping in a freezable state.
 pub const TASK_FREEZABLE: c_int = bindings::TASK_FREEZABLE as c_int;
 /// Convenience constant for waking up tasks regardless of whether they are in interruptible or
 /// uninterruptible sleep.
 pub const TASK_NORMAL: c_uint = bindings::TASK_NORMAL as c_uint;

 /// Returns the currently running task.
 #[macro_export]
 macro_rules! current {
     () => {
         // SAFETY: This expression creates a temporary value that is dropped at the end of the
         // caller's scope. The following mechanisms ensure that the resulting `&CurrentTask` cannot
         // leave current task context:
         //
         // * To return to userspace, the caller must leave the current scope.
         // * Operations such as `begin_new_exec()` are necessarily unsafe and the caller of
         //   `begin_new_exec()` is responsible for safety.
         // * Rust abstractions for things such as a `kthread_use_mm()` scope must require the
         //   closure to be `Send`, so the `NotThreadSafe` field of `CurrentTask` ensures that the
         //   `&CurrentTask` cannot cross the scope in either direction.
         unsafe { &*$crate::task::Task::current() }
     };
 }

 /// Wraps the kernel's `struct task_struct`.
 ///
 /// # Invariants
 ///
 /// All instances are valid tasks created by the C portion of the kernel.
 ///
 /// Instances of this type are always refcounted, that is, a call to `get_task_struct` ensures
 /// that the allocation remains valid at least until the matching call to `put_task_struct`.
 ///
 /// # Examples
 ///
 /// The following is an example of getting the PID of the current thread with zero additional cost
 /// when compared to the C version:
 ///
 /// ```
 /// let pid = current!().pid();
 /// ```
 ///
 /// Getting the PID of the current process, also zero additional cost:
 ///
 /// ```
 /// let pid = current!().group_leader().pid();
 /// ```
 ///
 /// Getting the current task and storing it in some struct. The reference count is automatically
 /// incremented when creating `State` and decremented when it is dropped:
 ///
 /// ```
 /// use kernel::{task::Task, types::ARef};
 ///
 /// struct State {
 ///     creator: ARef<Task>,
 ///     index: u32,
 /// }
 ///
 /// impl State {
 ///     fn new() -> Self {
 ///         Self {
 ///             creator: ARef::from(&**current!()),
 ///             index: 0,
 ///         }
 ///     }
 /// }
 /// ```
 #[repr(transparent)]
 pub struct Task(pub(crate) Opaque<bindings::task_struct>);

 // SAFETY: By design, the only way to access a `Task` is via the `current` function or via an
 // `ARef<Task>` obtained through the `AlwaysRefCounted` impl. This means that the only situation in
 // which a `Task` can be accessed mutably is when the refcount drops to zero and the destructor
 // runs. It is safe for that to happen on any thread, so it is ok for this type to be `Send`.
 unsafe impl Send for Task {}

 // SAFETY: It's OK to access `Task` through shared references from other threads because we're
 // either accessing properties that don't change (e.g., `pid`, `group_leader`) or that are properly
 // synchronised by C code (e.g., `signal_pending`).
 unsafe impl Sync for Task {}

 /// Represents the [`Task`] in the `current` global.
 ///
 /// This type exists to provide more efficient operations that are only valid on the current task.
 /// For example, to retrieve the pid-namespace of a task, you must use rcu protection unless it is
 /// the current task.
 ///
 /// # Invariants
 ///
 /// Each value of this type must only be accessed from the task context it was created within.
 ///
 /// Of course, every thread is in a different task context, but for the purposes of this invariant,
 /// these operations also permanently leave the task context:
 ///
 /// * Returning to userspace from system call context.
 /// * Calling `release_task()`.
 /// * Calling `begin_new_exec()` in a binary format loader.
 ///
 /// Other operations temporarily create a new sub-context:
 ///
 /// * Calling `kthread_use_mm()` creates a new context, and `kthread_unuse_mm()` returns to the
 ///   old context.
 ///
 /// This means that a `CurrentTask` obtained before a `kthread_use_mm()` call may be used again
 /// once `kthread_unuse_mm()` is called, but it must not be used between these two calls.
 /// Conversely, a `CurrentTask` obtained between a `kthread_use_mm()`/`kthread_unuse_mm()` pair
 /// must not be used after `kthread_unuse_mm()`.
 #[repr(transparent)]
 pub struct CurrentTask(Task, NotThreadSafe);

 // Make all `Task` methods available on `CurrentTask`.
 impl Deref for CurrentTask {
     type Target = Task;
     #[inline]
     fn deref(&self) -> &Task {
         &self.0
     }
 }

 /// The type of process identifiers (PIDs).
 pub type Pid = bindings::pid_t;

 /// The type of user identifiers (UIDs).
 #[derive(Copy, Clone)]
 pub struct Kuid {
     kuid: bindings::kuid_t,
 }

 impl Task {
     /// Returns a raw pointer to the current task.
     ///
     /// It is up to the user to use the pointer correctly.
     #[inline]
     pub fn current_raw() -> *mut bindings::task_struct {
         // SAFETY: Getting the current pointer is always safe.
         unsafe { bindings::get_current() }
     }

     /// Returns a task reference for the currently executing task/thread.
     ///
     /// The recommended way to get the current task/thread is to use the
     /// [`current`] macro because it is safe.
     ///
     /// # Safety
     ///
     /// Callers must ensure that the returned object is only used to access a [`CurrentTask`]
     /// within the task context that was active when this function was called. For more details,
     /// see the invariants section for [`CurrentTask`].
     #[inline]
     pub unsafe fn current() -> impl Deref<Target = CurrentTask> {
         struct TaskRef {
             task: *const CurrentTask,
         }

         impl Deref for TaskRef {
             type Target = CurrentTask;

             fn deref(&self) -> &Self::Target {
                 // SAFETY: The returned reference borrows from this `TaskRef`, so it cannot outlive
                 // the `TaskRef`, which the caller of `Task::current()` has promised will not
                 // outlive the task/thread for which `self.task` is the `current` pointer. Thus, it
                 // is okay to return a `CurrentTask` reference here.
                 unsafe { &*self.task }
             }
         }

         TaskRef {
             // CAST: The layout of `struct task_struct` and `CurrentTask` is identical.
             task: Task::current_raw().cast(),
         }
     }

     /// Returns a raw pointer to the task.
     #[inline]
     pub fn as_ptr(&self) -> *mut bindings::task_struct {
         self.0.get()
     }

     /// Returns the group leader of the given task.
     pub fn group_leader(&self) -> &Task {
         // SAFETY: The group leader of a task never changes after initialization, so reading this
         // field is not a data race.
         let ptr = unsafe { *ptr::addr_of!((*self.as_ptr()).group_leader) };

         // SAFETY: The lifetime of the returned task reference is tied to the lifetime of `self`,
         // and given that a task has a reference to its group leader, we know it must be valid for
         // the lifetime of the returned task reference.
         unsafe { &*ptr.cast() }
     }

     /// Returns the PID of the given task.
     pub fn pid(&self) -> Pid {
         // SAFETY: The pid of a task never changes after initialization, so reading this field is
         // not a data race.
         unsafe { *ptr::addr_of!((*self.as_ptr()).pid) }
     }

     /// Returns the UID of the given task.
     #[inline]
     pub fn uid(&self) -> Kuid {
         // SAFETY: It's always safe to call `task_uid` on a valid task.
         Kuid::from_raw(unsafe { bindings::task_uid(self.as_ptr()) })
     }

     /// Returns the effective UID of the given task.
     #[inline]
     pub fn euid(&self) -> Kuid {
         // SAFETY: It's always safe to call `task_euid` on a valid task.
         Kuid::from_raw(unsafe { bindings::task_euid(self.as_ptr()) })
     }

     /// Determines whether the given task has pending signals.
     #[inline]
     pub fn signal_pending(&self) -> bool {
         // SAFETY: It's always safe to call `signal_pending` on a valid task.
         unsafe { bindings::signal_pending(self.as_ptr()) != 0 }
     }

     /// Returns task's pid namespace with elevated reference count
     #[inline]
     pub fn get_pid_ns(&self) -> Option<ARef<PidNamespace>> {
         // SAFETY: By the type invariant, we know that `self.0` is valid.
         let ptr = unsafe { bindings::task_get_pid_ns(self.as_ptr()) };
         if ptr.is_null() {
             None
         } else {
             // SAFETY: `ptr` is valid by the safety requirements of this function. And we own a
             // reference count via `task_get_pid_ns()`.
             // CAST: `Self` is a `repr(transparent)` wrapper around `bindings::pid_namespace`.
             Some(unsafe { ARef::from_raw(ptr::NonNull::new_unchecked(ptr.cast::<PidNamespace>())) })
         }
     }

     /// Returns the given task's pid in the provided pid namespace.
     #[doc(alias = "task_tgid_nr_ns")]
     #[inline]
     pub fn tgid_nr_ns(&self, pidns: Option<&PidNamespace>) -> Pid {
         let pidns = match pidns {
             Some(pidns) => pidns.as_ptr(),
             None => core::ptr::null_mut(),
         };
         // SAFETY: By the type invariant, we know that `self.0` is valid. We received a valid
         // PidNamespace that we can use as a pointer or we received an empty PidNamespace and
         // thus pass a null pointer. The underlying C function is safe to be used with NULL
         // pointers.
         unsafe { bindings::task_tgid_nr_ns(self.as_ptr(), pidns) }
     }

     /// Wakes up the task.
     #[inline]
     pub fn wake_up(&self) {
         // SAFETY: It's always safe to call `wake_up_process` on a valid task, even if the task
         // running.
         unsafe { bindings::wake_up_process(self.as_ptr()) };
     }
 }

 impl CurrentTask {
     /// Access the address space of the current task.
     ///
     /// This function does not touch the refcount of the mm.
     #[inline]
     pub fn mm(&self) -> Option<&MmWithUser> {
         // SAFETY: The `mm` field of `current` is not modified from other threads, so reading it is
         // not a data race.
         let mm = unsafe { (*self.as_ptr()).mm };

         if mm.is_null() {
             return None;
         }

         // SAFETY: If `current->mm` is non-null, then it references a valid mm with a non-zero
         // value of `mm_users`. Furthermore, the returned `&MmWithUser` borrows from this
         // `CurrentTask`, so it cannot escape the scope in which the current pointer was obtained.
         //
         // This is safe even if `kthread_use_mm()`/`kthread_unuse_mm()` are used. There are two
         // relevant cases:
         // * If the `&CurrentTask` was created before `kthread_use_mm()`, then it cannot be
         //   accessed during the `kthread_use_mm()`/`kthread_unuse_mm()` scope due to the
         //   `NotThreadSafe` field of `CurrentTask`.
         // * If the `&CurrentTask` was created within a `kthread_use_mm()`/`kthread_unuse_mm()`
         //   scope, then the `&CurrentTask` cannot escape that scope, so the returned `&MmWithUser`
         //   also cannot escape that scope.
         // In either case, it's not possible to read `current->mm` and keep using it after the
         // scope is ended with `kthread_unuse_mm()`.
         Some(unsafe { MmWithUser::from_raw(mm) })
     }

     /// Access the pid namespace of the current task.
     ///
     /// This function does not touch the refcount of the namespace or use RCU protection.
     ///
     /// To access the pid namespace of another task, see [`Task::get_pid_ns`].
     #[doc(alias = "task_active_pid_ns")]
     #[inline]
     pub fn active_pid_ns(&self) -> Option<&PidNamespace> {
         // SAFETY: It is safe to call `task_active_pid_ns` without RCU protection when calling it
         // on the current task.
         let active_ns = unsafe { bindings::task_active_pid_ns(self.as_ptr()) };

         if active_ns.is_null() {
             return None;
         }

         // The lifetime of `PidNamespace` is bound to `Task` and `struct pid`.
         //
         // The `PidNamespace` of a `Task` doesn't ever change once the `Task` is alive.
         //
         // From system call context retrieving the `PidNamespace` for the current task is always
         // safe and requires neither RCU locking nor a reference count to be held. Retrieving the
         // `PidNamespace` after `release_task()` for current will return `NULL` but no codepath
         // like that is exposed to Rust.
         //
         // SAFETY: If `current`'s pid ns is non-null, then it references a valid pid ns.
         // Furthermore, the returned `&PidNamespace` borrows from this `CurrentTask`, so it cannot
         // escape the scope in which the current pointer was obtained, e.g. it cannot live past a
         // `release_task()` call.
         Some(unsafe { PidNamespace::from_ptr(active_ns) })
     }
 }

 // SAFETY: The type invariants guarantee that `Task` is always refcounted.
 unsafe impl crate::types::AlwaysRefCounted for Task {
     #[inline]
     fn inc_ref(&self) {
         // SAFETY: The existence of a shared reference means that the refcount is nonzero.
         unsafe { bindings::get_task_struct(self.as_ptr()) };
     }

     #[inline]
     unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
         // SAFETY: The safety requirements guarantee that the refcount is nonzero.
         unsafe { bindings::put_task_struct(obj.cast().as_ptr()) }
     }
 }

 impl Kuid {
     /// Get the current euid.
     #[inline]
     pub fn current_euid() -> Kuid {
         // SAFETY: Just an FFI call.
         Self::from_raw(unsafe { bindings::current_euid() })
     }

     /// Create a `Kuid` given the raw C type.
     #[inline]
     pub fn from_raw(kuid: bindings::kuid_t) -> Self {
         Self { kuid }
     }

     /// Turn this kuid into the raw C type.
     #[inline]
     pub fn into_raw(self) -> bindings::kuid_t {
         self.kuid
     }

     /// Converts this kernel UID into a userspace UID.
     ///
     /// Uses the namespace of the current task.
     #[inline]
     pub fn into_uid_in_current_ns(self) -> bindings::uid_t {
         // SAFETY: Just an FFI call.
         unsafe { bindings::from_kuid(bindings::current_user_ns(), self.kuid) }
     }
 }

 impl PartialEq for Kuid {
     #[inline]
     fn eq(&self, other: &Kuid) -> bool {
         // SAFETY: Just an FFI call.
         unsafe { bindings::uid_eq(self.kuid, other.kuid) }
     }
 }

 impl Eq for Kuid {}

 /// Annotation for functions that can sleep.
 ///
 /// Equivalent to the C side [`might_sleep()`], this function serves as
 /// a debugging aid and a potential scheduling point.
 ///
 /// This function can only be used in a nonatomic context.
 ///
 /// [`might_sleep()`]: https://docs.kernel.org/driver-api/basics.html#c.might_sleep
 #[track_caller]
 #[inline]
 pub fn might_sleep() {
     #[cfg(CONFIG_DEBUG_ATOMIC_SLEEP)]
     {
         let loc = core::panic::Location::caller();
         let file = kernel::file_from_location(loc);

         // SAFETY: `file.as_ptr()` is valid for reading and guaranteed to be nul-terminated.
         unsafe { crate::bindings::__might_sleep(file.as_ptr().cast(), loc.line() as i32) }
     }

     // SAFETY: Always safe to call.
     unsafe { crate::bindings::might_resched() }
 }
	// SPDX-License-Identifier: GPL-2.0

	//! Tasks (threads and processes).
	//!
	//! C header: [`include/linux/sched.h`](srctree/include/linux/sched.h).

	use crate::{
	bindings,
	ffi::{c_int, c_long, c_uint},
	mm::MmWithUser,
	pid_namespace::PidNamespace,
	types::{ARef, NotThreadSafe, Opaque},
	};
	use core::{
	cmp::{Eq, PartialEq},
	ops::Deref,
	ptr,
	};

	/// A sentinel value used for infinite timeouts.
	pub const MAX_SCHEDULE_TIMEOUT: c_long = c_long::MAX;

	/// Bitmask for tasks that are sleeping in an interruptible state.
	pub const TASK_INTERRUPTIBLE: c_int = bindings::TASK_INTERRUPTIBLE as c_int;
	/// Bitmask for tasks that are sleeping in an uninterruptible state.
	pub const TASK_UNINTERRUPTIBLE: c_int = bindings::TASK_UNINTERRUPTIBLE as c_int;
	/// Bitmask for tasks that are sleeping in a freezable state.
	pub const TASK_FREEZABLE: c_int = bindings::TASK_FREEZABLE as c_int;
	/// Convenience constant for waking up tasks regardless of whether they are in interruptible or
	/// uninterruptible sleep.
	pub const TASK_NORMAL: c_uint = bindings::TASK_NORMAL as c_uint;

	/// Returns the currently running task.
	#[macro_export]
	macro_rules! current {
	() => {
	// SAFETY: This expression creates a temporary value that is dropped at the end of the
	// caller's scope. The following mechanisms ensure that the resulting `&CurrentTask` cannot
	// leave current task context:
	//
	// * To return to userspace, the caller must leave the current scope.
	// * Operations such as `begin_new_exec()` are necessarily unsafe and the caller of
	// `begin_new_exec()` is responsible for safety.
	// * Rust abstractions for things such as a `kthread_use_mm()` scope must require the
	// closure to be `Send`, so the `NotThreadSafe` field of `CurrentTask` ensures that the
	// `&CurrentTask` cannot cross the scope in either direction.
	unsafe { &*$crate::task::Task::current() }
	};
	}

	/// Wraps the kernel's `struct task_struct`.
	///
	/// # Invariants
	///
	/// All instances are valid tasks created by the C portion of the kernel.
	///
	/// Instances of this type are always refcounted, that is, a call to `get_task_struct` ensures
	/// that the allocation remains valid at least until the matching call to `put_task_struct`.
	///
	/// # Examples
	///
	/// The following is an example of getting the PID of the current thread with zero additional cost
	/// when compared to the C version:
	///
	/// ```
	/// let pid = current!().pid();
	/// ```
	///
	/// Getting the PID of the current process, also zero additional cost:
	///
	/// ```
	/// let pid = current!().group_leader().pid();
	/// ```
	///
	/// Getting the current task and storing it in some struct. The reference count is automatically
	/// incremented when creating `State` and decremented when it is dropped:
	///
	/// ```
	/// use kernel::{task::Task, types::ARef};
	///
	/// struct State {
	/// creator: ARef<Task>,
	/// index: u32,
	/// }
	///
	/// impl State {
	/// fn new() -> Self {
	/// Self {
	/// creator: ARef::from(&**current!()),
	/// index: 0,
	/// }
	/// }
	/// }
	/// ```
	#[repr(transparent)]
	pub struct Task(pub(crate) Opaque<bindings::task_struct>);

	// SAFETY: By design, the only way to access a `Task` is via the `current` function or via an
	// `ARef<Task>` obtained through the `AlwaysRefCounted` impl. This means that the only situation in
	// which a `Task` can be accessed mutably is when the refcount drops to zero and the destructor
	// runs. It is safe for that to happen on any thread, so it is ok for this type to be `Send`.
	unsafe impl Send for Task {}

	// SAFETY: It's OK to access `Task` through shared references from other threads because we're
	// either accessing properties that don't change (e.g., `pid`, `group_leader`) or that are properly
	// synchronised by C code (e.g., `signal_pending`).
	unsafe impl Sync for Task {}

	/// Represents the [`Task`] in the `current` global.
	///
	/// This type exists to provide more efficient operations that are only valid on the current task.
	/// For example, to retrieve the pid-namespace of a task, you must use rcu protection unless it is
	/// the current task.
	///
	/// # Invariants
	///
	/// Each value of this type must only be accessed from the task context it was created within.
	///
	/// Of course, every thread is in a different task context, but for the purposes of this invariant,
	/// these operations also permanently leave the task context:
	///
	/// * Returning to userspace from system call context.
	/// * Calling `release_task()`.
	/// * Calling `begin_new_exec()` in a binary format loader.
	///
	/// Other operations temporarily create a new sub-context:
	///
	/// * Calling `kthread_use_mm()` creates a new context, and `kthread_unuse_mm()` returns to the
	/// old context.
	///
	/// This means that a `CurrentTask` obtained before a `kthread_use_mm()` call may be used again
	/// once `kthread_unuse_mm()` is called, but it must not be used between these two calls.
	/// Conversely, a `CurrentTask` obtained between a `kthread_use_mm()`/`kthread_unuse_mm()` pair
	/// must not be used after `kthread_unuse_mm()`.
	#[repr(transparent)]
	pub struct CurrentTask(Task, NotThreadSafe);

	// Make all `Task` methods available on `CurrentTask`.
	impl Deref for CurrentTask {
	type Target = Task;
	#[inline]
	fn deref(&self) -> &Task {
	&self.0
	}
	}

	/// The type of process identifiers (PIDs).
	pub type Pid = bindings::pid_t;

	/// The type of user identifiers (UIDs).
	#[derive(Copy, Clone)]
	pub struct Kuid {
	kuid: bindings::kuid_t,
	}

	impl Task {
	/// Returns a raw pointer to the current task.
	///
	/// It is up to the user to use the pointer correctly.
	#[inline]
	pub fn current_raw() -> *mut bindings::task_struct {
	// SAFETY: Getting the current pointer is always safe.
	unsafe { bindings::get_current() }
	}

	/// Returns a task reference for the currently executing task/thread.
	///
	/// The recommended way to get the current task/thread is to use the
	/// [`current`] macro because it is safe.
	///
	/// # Safety
	///
	/// Callers must ensure that the returned object is only used to access a [`CurrentTask`]
	/// within the task context that was active when this function was called. For more details,
	/// see the invariants section for [`CurrentTask`].
	#[inline]
	pub unsafe fn current() -> impl Deref<Target = CurrentTask> {
	struct TaskRef {
	task: *const CurrentTask,
	}

	impl Deref for TaskRef {
	type Target = CurrentTask;

	fn deref(&self) -> &Self::Target {
	// SAFETY: The returned reference borrows from this `TaskRef`, so it cannot outlive
	// the `TaskRef`, which the caller of `Task::current()` has promised will not
	// outlive the task/thread for which `self.task` is the `current` pointer. Thus, it
	// is okay to return a `CurrentTask` reference here.
	unsafe { &*self.task }
	}
	}

	TaskRef {
	// CAST: The layout of `struct task_struct` and `CurrentTask` is identical.
	task: Task::current_raw().cast(),
	}
	}

	/// Returns a raw pointer to the task.
	#[inline]
	pub fn as_ptr(&self) -> *mut bindings::task_struct {
	self.0.get()
	}

	/// Returns the group leader of the given task.
	pub fn group_leader(&self) -> &Task {
	// SAFETY: The group leader of a task never changes after initialization, so reading this
	// field is not a data race.
	let ptr = unsafe { ptr::addr_of!((self.as_ptr()).group_leader) };

	// SAFETY: The lifetime of the returned task reference is tied to the lifetime of `self`,
	// and given that a task has a reference to its group leader, we know it must be valid for
	// the lifetime of the returned task reference.
	unsafe { &*ptr.cast() }
	}

	/// Returns the PID of the given task.
	pub fn pid(&self) -> Pid {
	// SAFETY: The pid of a task never changes after initialization, so reading this field is
	// not a data race.
	unsafe { ptr::addr_of!((self.as_ptr()).pid) }
	}

	/// Returns the UID of the given task.
	#[inline]
	pub fn uid(&self) -> Kuid {
	// SAFETY: It's always safe to call `task_uid` on a valid task.
	Kuid::from_raw(unsafe { bindings::task_uid(self.as_ptr()) })
	}

	/// Returns the effective UID of the given task.
	#[inline]
	pub fn euid(&self) -> Kuid {
	// SAFETY: It's always safe to call `task_euid` on a valid task.
	Kuid::from_raw(unsafe { bindings::task_euid(self.as_ptr()) })
	}

	/// Determines whether the given task has pending signals.
	#[inline]
	pub fn signal_pending(&self) -> bool {
	// SAFETY: It's always safe to call `signal_pending` on a valid task.
	unsafe { bindings::signal_pending(self.as_ptr()) != 0 }
	}

	/// Returns task's pid namespace with elevated reference count
	#[inline]
	pub fn get_pid_ns(&self) -> Option<ARef<PidNamespace>> {
	// SAFETY: By the type invariant, we know that `self.0` is valid.
	let ptr = unsafe { bindings::task_get_pid_ns(self.as_ptr()) };
	if ptr.is_null() {
	None
	} else {
	// SAFETY: `ptr` is valid by the safety requirements of this function. And we own a
	// reference count via `task_get_pid_ns()`.
	// CAST: `Self` is a `repr(transparent)` wrapper around `bindings::pid_namespace`.
	Some(unsafe { ARef::from_raw(ptr::NonNull::new_unchecked(ptr.cast::<PidNamespace>())) })
	}
	}

	/// Returns the given task's pid in the provided pid namespace.
	#[doc(alias = "task_tgid_nr_ns")]
	#[inline]
	pub fn tgid_nr_ns(&self, pidns: Option<&PidNamespace>) -> Pid {
	let pidns = match pidns {
	Some(pidns) => pidns.as_ptr(),
	None => core::ptr::null_mut(),
	};
	// SAFETY: By the type invariant, we know that `self.0` is valid. We received a valid
	// PidNamespace that we can use as a pointer or we received an empty PidNamespace and
	// thus pass a null pointer. The underlying C function is safe to be used with NULL
	// pointers.
	unsafe { bindings::task_tgid_nr_ns(self.as_ptr(), pidns) }
	}

	/// Wakes up the task.
	#[inline]
	pub fn wake_up(&self) {
	// SAFETY: It's always safe to call `wake_up_process` on a valid task, even if the task
	// running.
	unsafe { bindings::wake_up_process(self.as_ptr()) };
	}
	}

	impl CurrentTask {
	/// Access the address space of the current task.
	///
	/// This function does not touch the refcount of the mm.
	#[inline]
	pub fn mm(&self) -> Option<&MmWithUser> {
	// SAFETY: The `mm` field of `current` is not modified from other threads, so reading it is
	// not a data race.
	let mm = unsafe { (*self.as_ptr()).mm };

	if mm.is_null() {
	return None;
	}

	// SAFETY: If `current->mm` is non-null, then it references a valid mm with a non-zero
	// value of `mm_users`. Furthermore, the returned `&MmWithUser` borrows from this
	// `CurrentTask`, so it cannot escape the scope in which the current pointer was obtained.
	//
	// This is safe even if `kthread_use_mm()`/`kthread_unuse_mm()` are used. There are two
	// relevant cases:
	// * If the `&CurrentTask` was created before `kthread_use_mm()`, then it cannot be
	// accessed during the `kthread_use_mm()`/`kthread_unuse_mm()` scope due to the
	// `NotThreadSafe` field of `CurrentTask`.
	// * If the `&CurrentTask` was created within a `kthread_use_mm()`/`kthread_unuse_mm()`
	// scope, then the `&CurrentTask` cannot escape that scope, so the returned `&MmWithUser`
	// also cannot escape that scope.
	// In either case, it's not possible to read `current->mm` and keep using it after the
	// scope is ended with `kthread_unuse_mm()`.
	Some(unsafe { MmWithUser::from_raw(mm) })
	}

	/// Access the pid namespace of the current task.
	///
	/// This function does not touch the refcount of the namespace or use RCU protection.
	///
	/// To access the pid namespace of another task, see [`Task::get_pid_ns`].
	#[doc(alias = "task_active_pid_ns")]
	#[inline]
	pub fn active_pid_ns(&self) -> Option<&PidNamespace> {
	// SAFETY: It is safe to call `task_active_pid_ns` without RCU protection when calling it
	// on the current task.
	let active_ns = unsafe { bindings::task_active_pid_ns(self.as_ptr()) };

	if active_ns.is_null() {
	return None;
	}

	// The lifetime of `PidNamespace` is bound to `Task` and `struct pid`.
	//
	// The `PidNamespace` of a `Task` doesn't ever change once the `Task` is alive.
	//
	// From system call context retrieving the `PidNamespace` for the current task is always
	// safe and requires neither RCU locking nor a reference count to be held. Retrieving the
	// `PidNamespace` after `release_task()` for current will return `NULL` but no codepath
	// like that is exposed to Rust.
	//
	// SAFETY: If `current`'s pid ns is non-null, then it references a valid pid ns.
	// Furthermore, the returned `&PidNamespace` borrows from this `CurrentTask`, so it cannot
	// escape the scope in which the current pointer was obtained, e.g. it cannot live past a
	// `release_task()` call.
	Some(unsafe { PidNamespace::from_ptr(active_ns) })
	}
	}

	// SAFETY: The type invariants guarantee that `Task` is always refcounted.
	unsafe impl crate::types::AlwaysRefCounted for Task {
	#[inline]
	fn inc_ref(&self) {
	// SAFETY: The existence of a shared reference means that the refcount is nonzero.
	unsafe { bindings::get_task_struct(self.as_ptr()) };
	}

	#[inline]
	unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
	// SAFETY: The safety requirements guarantee that the refcount is nonzero.
	unsafe { bindings::put_task_struct(obj.cast().as_ptr()) }
	}
	}

	impl Kuid {
	/// Get the current euid.
	#[inline]
	pub fn current_euid() -> Kuid {
	// SAFETY: Just an FFI call.
	Self::from_raw(unsafe { bindings::current_euid() })
	}

	/// Create a `Kuid` given the raw C type.
	#[inline]
	pub fn from_raw(kuid: bindings::kuid_t) -> Self {
	Self { kuid }
	}

	/// Turn this kuid into the raw C type.
	#[inline]
	pub fn into_raw(self) -> bindings::kuid_t {
	self.kuid
	}

	/// Converts this kernel UID into a userspace UID.
	///
	/// Uses the namespace of the current task.
	#[inline]
	pub fn into_uid_in_current_ns(self) -> bindings::uid_t {
	// SAFETY: Just an FFI call.
	unsafe { bindings::from_kuid(bindings::current_user_ns(), self.kuid) }
	}
	}

	impl PartialEq for Kuid {
	#[inline]
	fn eq(&self, other: &Kuid) -> bool {
	// SAFETY: Just an FFI call.
	unsafe { bindings::uid_eq(self.kuid, other.kuid) }
	}
	}

	impl Eq for Kuid {}

	/// Annotation for functions that can sleep.
	///
	/// Equivalent to the C side [`might_sleep()`], this function serves as
	/// a debugging aid and a potential scheduling point.
	///
	/// This function can only be used in a nonatomic context.
	///
	/// [`might_sleep()`]: https://docs.kernel.org/driver-api/basics.html#c.might_sleep
	#[track_caller]
	#[inline]
	pub fn might_sleep() {
	#[cfg(CONFIG_DEBUG_ATOMIC_SLEEP)]
	{
	let loc = core::panic::Location::caller();
	let file = kernel::file_from_location(loc);

	// SAFETY: `file.as_ptr()` is valid for reading and guaranteed to be nul-terminated.
	unsafe { crate::bindings::__might_sleep(file.as_ptr().cast(), loc.line() as i32) }
	}

	// SAFETY: Always safe to call.
	unsafe { crate::bindings::might_resched() }
	}