Threading Primitives

of thread identity. Every thread-aware syscall (gettid, set_tid_address,. Why it matters: The current Process struct has only pid and no concept. Focus on `tid` and `tgid` in `kernel/src/process/mod.rs` while you trace the snippet.

/// Descriptor for a single userspace process.
pub struct Process {
    /// This process's unique identifier.
    pub pid: Pid,
    pub tid: u32,
    pub tgid: u32,
    pub clear_child_tid: u64,
    /// Parent PID.  0 means no parent (init or an orphan).
    pub ppid: Pid,
    /// Current lifecycle state.
    pub state: ProcessState,
    /// Root physical address of this process's page table.
    ///
    /// `None` means the process has not yet been assigned a dedicated
    /// address space and shares the kernel's mappings (pre-Phase 12).
    pub page_table_root: Option<x86_64::PhysAddr>,
    /// Top of this process's kernel-mode stack (virtual address).
    pub kernel_stack_top: u64,
    /// Userspace entry-point virtual address.
    pub entry_point: u64,
    /// Initial userspace RSP: the virtual address of `argc` on the ABI stack,
    /// as returned by `setup_abi_stack`.  This is **not** the raw top of the
    /// stack allocation — it points into the stack, below the argv/envp data.
    pub user_stack_top: u64,

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gettid() to return their unique TID so musl can track thread identity for. Why it matters: Syscall 186 currently aliases to sys_getpid(). Threads need. Focus on `gettid` and `sys_gettid` in `kernel/src/arch/x86_64/syscall.rs` while you trace the snippet.

/// `gettid()` — return the calling thread's unique thread ID.
fn sys_gettid() -> u64 {
    let pid = crate::process::current_pid();
    crate::process::PROCESS_TABLE
        .lock()
        .find(pid)
        .map(|p| p.tid as u64)
        .unwrap_or(pid as u64)
}

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synchronization. Every pthread_mutex_lock that contends, every pthread_cond_wait,. Why it matters: The futex table is the core kernel data structure for thread. Focus on `FUTEX_TABLE` and `FutexWaiter` in `kernel/src/process/futex.rs` while you trace the snippet.

/// Global table of futex wait queues, keyed by `(page_table_root, vaddr)`.
pub static FUTEX_TABLE: Lazy<Mutex<BTreeMap<FutexKey, Vec<FutexWaiter>>>> =
    Lazy::new(|| Mutex::new(BTreeMap::new()));

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