linux-2.6.18源码分析笔记---进程

在目录include\linux\sched.h下定义了进程描述符task_struct，关注如下字段：

进程状态

volatile long state：表示进程状态，在该文件头部有几种状态的取值。

long exit_state：表示进程退出状态，下面的定义中前缀为EXIT的表示该字段取值，表示进程退出状态

/*
 * Task state bitmask. NOTE! These bits are also
 * encoded in fs/proc/array.c: get_task_state().
 *
 * We have two separate sets of flags: task->state
 * is about runnability, while task->exit_state are
 * about the task exiting. Confusing, but this way
 * modifying one set can't modify the other one by
 * mistake.
 */
#define TASK_RUNNING        0
#define TASK_INTERRUPTIBLE    1
#define TASK_UNINTERRUPTIBLE    2
#define TASK_STOPPED        4
#define TASK_TRACED        8
/* in tsk->exit_state */
#define EXIT_ZOMBIE        16
#define EXIT_DEAD        32
/* in tsk->state again */
#define TASK_NONINTERACTIVE    64

#define __set_task_state(tsk, state_value)        \
    do { (tsk)->state = (state_value); } while (0)
#define set_task_state(tsk, state_value)        \
    set_mb((tsk)->state, (state_value))

/*
 * set_current_state() includes a barrier so that the write of current->state
 * is correctly serialised wrt the caller's subsequent test of whether to
 * actually sleep:
 *
 *    set_current_state(TASK_UNINTERRUPTIBLE);
 *    if (do_i_need_to_sleep())
 *        schedule();
 *
 * If the caller does not need such serialisation then use __set_current_state()
 */
#define __set_current_state(state_value)            \
    do { current->state = (state_value); } while (0)
#define set_current_state(state_value)        \
    set_mb(current->state, (state_value))

statue取值和操作