Struct SwitchTarget 

pub(super) struct SwitchTarget {
    pub(super) old_rsp_ptr: *mut u64,
    pub(super) new_rsp_ptr: *const u64,
    pub(super) old_fpu_ptr: *mut u8,
    pub(super) new_fpu_ptr: *const u8,
    pub(super) old_xcr0: u64,
    pub(super) new_xcr0: u64,
}

Information needed to perform a context switch after releasing the lock.

Safety invariants

SwitchTarget contains raw pointers into Arc<Task> objects. All five invariants below must hold at the moment do_switch_context / switch_context reads them. They are established by yield_cpu_local under the LOCAL lock and consumed before any other CPU can observe the pointed-to memory.

1. old_rsp_ptr points to (*source.context.get()).saved_rsp. The source Arc is kept alive by cpu.current_task or cpu.task_to_requeue for the duration of the switch; no migration, reap, or exit can invalidate it while the lock is held.

2. new_rsp_ptr points to (*target.context.get()).saved_rsp. Same lifetime guarantee as above: target is in cpu.current_task.

3. old_fpu_ptr / new_fpu_ptr point into the FPU state areas of the source / target tasks respectively. These areas sit inside the kernel stack and are valid as long as the owning Arc<Task> is alive. FPU state is never modified concurrently: the switch context owns it exclusively between the save and restore.

4. old_xcr0 / new_xcr0 are the XCR0 masks of source and target, read atomically from task.xcr0_mask. They are only consumed by the switch assembly which toggles XCR0 around xsave/xrstor.

5. Lifetime: SwitchTarget must not outlive the LOCAL lock that protected its construction. It is consumed by do_switch_context immediately after the lock is released, before any allocation, IPI, or scheduler operation.

Debug checks

Under cfg(debug_assertions), prepare_switch_target validates that old_rsp / new_rsp fall within their respective kernel stacks before returning this struct.

Fields

old_rsp_ptr: *mut u64

new_rsp_ptr: *const u64

old_fpu_ptr: *mut u8

new_fpu_ptr: *const u8

old_xcr0: u64

new_xcr0: u64

Trait Implementations

impl Send for SwitchTarget