Operating System (4) : 内核线程管理

// alloc_proc - alloc a proc_struct and init all fields of proc_struct
static struct proc_struct *
alloc_proc(void) {
    struct proc_struct *proc = kmalloc(sizeof(struct proc_struct));
    if (proc != NULL) {
    //LAB4:EXERCISE1
    /*
     * below fields in proc_struct need to be initialized
     *       enum proc_state state;                      // Process state
     *       int pid;                                    // Process ID
     *       int runs;                                   // the running times of Proces
     *       uintptr_t kstack;                           // Process kernel stack
     *       volatile bool need_resched;                 // bool value: need to be rescheduled to release CPU?
     *       struct proc_struct *parent;                 // the parent process
     *       struct mm_struct *mm;                       // Process's memory management field
     *       struct context context;                     // Switch here to run process
     *       struct trapframe *tf;                       // Trap frame for current interrupt
     *       uintptr_t cr3;                              // CR3 register: the base addr of Page Directroy Table(PDT)
     *       uint32_t flags;                             // Process flag
     *       char name[PROC_NAME_LEN + 1];               // Process name
     */
        proc->state = PROC_UNINIT;

        proc->pid = -1;
        proc->runs = 0;
        proc->kstack = 0;
        proc->need_resched = 0;
        proc->parent = NULL;
        proc->mm = NULL;

        memset(&(proc->context), 0, sizeof(struct context));
        proc->tf = NULL;
        proc->cr3 = boot_cr3;
        proc->flags = 0;

        memset(proc->name, 0, PROC_NAME_LEN);
    }
    return proc;
}

/* do_fork -     parent process for a new child process
 * @clone_flags: used to guide how to clone the child process
 * @stack:       the parent's user stack pointer. if stack==0, It means to fork a kernel thread.
 * @tf:          the trapframe info, which will be copied to child process's proc->tf
 */
int
do_fork(uint32_t clone_flags, uintptr_t stack, struct trapframe *tf) {
    int ret = -E_NO_FREE_PROC;
    struct proc_struct *proc;
    if (nr_process >= MAX_PROCESS) {
        goto fork_out;
    }
    ret = -E_NO_MEM;
    //LAB4:EXERCISE2 
    /*
     * Some Useful MACROs, Functions and DEFINEs, you can use them in below implementation.
     * MACROs or Functions:
     *   alloc_proc:   create a proc struct and init fields (lab4:exercise1)
     *   setup_kstack: alloc pages with size KSTACKPAGE as process kernel stack
     *   copy_mm:      process "proc" duplicate OR share process "current"'s mm according clone_flags
     *                 if clone_flags & CLONE_VM, then "share" ; else "duplicate"
     *   copy_thread:  setup the trapframe on the  process's kernel stack top and
     *                 setup the kernel entry point and stack of process
     *   hash_proc:    add proc into proc hash_list
     *   get_pid:      alloc a unique pid for process
     *   wakup_proc:   set proc->state = PROC_RUNNABLE
     * VARIABLES:
     *   proc_list:    the process set's list
     *   nr_process:   the number of process set
     */

    //    1. call alloc_proc to allocate a proc_struct
    //    2. call setup_kstack to allocate a kernel stack for child process
    //    3. call copy_mm to dup OR share mm according clone_flag
    //    4. call copy_thread to setup tf & context in proc_struct
    //    5. insert proc_struct into hash_list && proc_list
    //    6. call wakup_proc to make the new child process RUNNABLE
    //    7. set ret vaule using child proc's pid

    if ((proc = alloc_proc()) == NULL)
        goto fork_out;


    proc->parent = current;

    if (setup_kstack(proc) != 0)
        goto bad_fork_cleanup_proc;

    if (copy_mm(clone_flags, proc) != 0)
        goto bad_fork_cleanup_kstack;

    copy_thread(proc, stack, tf);

    bool intr_flag;

    local_intr_save(intr_flag);
    {
        proc->pid = get_pid();
        hash_proc(proc);
        list_add(&proc_list, &(proc->list_link));
        nr_process ++;
    }
    local_intr_restore(intr_flag);

    wakeup_proc(proc);

    ret = proc->pid;

fork_out:
    return ret;

bad_fork_cleanup_kstack:
    put_kstack(proc);
bad_fork_cleanup_proc:
    kfree(proc);
    goto fork_out;
}

proc->pid = get_pid();

// get_pid - alloc a unique pid for process
static int
get_pid(void) {
    static_assert(MAX_PID > MAX_PROCESS);
    struct proc_struct *proc;
    list_entry_t *list = &proc_list, *le;
    static int next_safe = MAX_PID, last_pid = MAX_PID;
    if (++ last_pid >= MAX_PID) {
        last_pid = 1;
        goto inside;
    }
    if (last_pid >= next_safe) {
    inside:
        next_safe = MAX_PID;
    repeat:
        le = list;
        while ((le = list_next(le)) != list) {
            proc = le2proc(le, list_link);
            if (proc->pid == last_pid) {
                if (++ last_pid >= next_safe) {
                    if (last_pid >= MAX_PID) {
                        last_pid = 1;
                    }
                    next_safe = MAX_PID;
                    goto repeat;
                }
            }
            else if (proc->pid > last_pid && next_safe > proc->pid) {
                next_safe = proc->pid;
            }
        }
    }
    return last_pid;
}

static inline bool
__intr_save(void) {
    if (read_eflags() & FL_IF) {
        intr_disable();
        return 1;
    }
    return 0;
}

static inline void
__intr_restore(bool flag) {
    if (flag) {
        intr_enable();
    }
}

#define local_intr_save(x)      do { x = __intr_save(); } while (0)
#define local_intr_restore(x)   __intr_restore(x);