Struct TaskContext

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pub struct TaskContext { /* private fields */ }

Available on crate feature context only.

Expand description

Saved hardware states of a task.

The context usually includes:

Callee-saved registers
Stack pointer register
Thread pointer register (for kernel-space thread-local storage)
FP/SIMD registers

On context switch, current task saves its context from CPU to memory, and the next task restores its context from memory to CPU.

Implementations§

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impl TaskContext

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pub fn new() -> Self

Creates a dummy context for a new task.

Note the context is not initialized, it will be filled by switch_to (for initial tasks) and init (for regular tasks) methods.

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pub fn init( &mut self, entry: usize, kstack_top: VirtAddr, kernel_tls: KernelTlsBase, )

Initializes the context for a new task, with the given entry point and kernel stack.

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pub fn set_task_anchor(&mut self, header: TaskAnchor)

Sets the pinned task-owned runtime task anchor.

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pub const fn task_anchor(&self) -> Option<TaskAnchor>

Returns the configured task-owned runtime task anchor.

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pub fn clone_user_fp_state_into(&self, child: &mut Self)

Available on crate features fp-simd and uspace only.

Saves the running parent’s hardware FP image into an unpublished child.

The runtime must pin the parent CPU while calling this method. Kernel code uses the soft-float ABI; eager task switching keeps the parent’s user register image live across kernel entry and preemption.

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pub fn prepare_switch_to(&mut self, _next_ctx: &Self)

Completes FP/SIMD work before current-context publication.

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pub unsafe fn switch_to(&mut self, next_ctx: &Self)

Performs only the final GPR/current/TLS transfer.

§Safety

Scheduling must be serialized, FP state prepared, and the next current anchor published. Both contexts and their anchors must remain pinned and alive. IRQs must remain disabled from publication through this call, with no intervening fallible or ownership-sensitive work.