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Diffstat (limited to 'rust/kernel/task.rs')
| -rw-r--r-- | rust/kernel/task.rs | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs new file mode 100644 index 000000000000..d70cad131956 --- /dev/null +++ b/rust/kernel/task.rs @@ -0,0 +1,75 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Tasks (threads and processes). +//! +//! C header: [`include/linux/sched.h`](../../../../include/linux/sched.h). + +use crate::{bindings, types::Opaque}; +use core::ptr; + +/// 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 ref-counted, that is, a call to `get_task_struct` ensures +/// that the allocation remains valid at least until the matching call to `put_task_struct`. +#[repr(transparent)] +pub struct Task(pub(crate) Opaque<bindings::task_struct>); + +// SAFETY: It's OK to access `Task` through 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 {} + +/// The type of process identifiers (PIDs). +type Pid = bindings::pid_t; + +impl Task { + /// Returns the group leader of the given task. + pub fn group_leader(&self) -> &Task { + // SAFETY: By the type invariant, we know that `self.0` is a valid task. Valid tasks always + // have a valid group_leader. + let ptr = unsafe { *ptr::addr_of!((*self.0.get()).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: By the type invariant, we know that `self.0` is a valid task. Valid tasks always + // have a valid pid. + unsafe { *ptr::addr_of!((*self.0.get()).pid) } + } + + /// Determines whether the given task has pending signals. + pub fn signal_pending(&self) -> bool { + // SAFETY: By the type invariant, we know that `self.0` is valid. + unsafe { bindings::signal_pending(self.0.get()) != 0 } + } + + /// Wakes up the task. + pub fn wake_up(&self) { + // SAFETY: By the type invariant, we know that `self.0.get()` is non-null and valid. + // And `wake_up_process` is safe to be called for any valid task, even if the task is + // running. + unsafe { bindings::wake_up_process(self.0.get()) }; + } +} + +// SAFETY: The type invariants guarantee that `Task` is always ref-counted. +unsafe impl crate::types::AlwaysRefCounted for Task { + fn inc_ref(&self) { + // SAFETY: The existence of a shared reference means that the refcount is nonzero. + unsafe { bindings::get_task_struct(self.0.get()) }; + } + + 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()) } + } +} |