一个进程在ｓｌｅｅｐ状态如何获取进程的调用栈
TASK_WAKEUPKILL状态
一个进程sleep了，我如何获取他的用户态栈，如何获取用户堆栈
如何在内核态打印用户态+内核态的栈?
确定上一个调用栈
group_exit_task的设置发生在函数fs/exec.c里面
./fs/coredump.c:340: tsk->signal->group_exit_task = tsk; 是一个de_thread
./fs/coredump.c:450: current->signal->group_exit_task = NULL;
./fs/exec.c:1062: sig->group_exit_task = tsk;
./fs/exec.c:1090: * exit_notify() can't miss ->group_exit_task
./fs/exec.c:1160: sig->group_exit_task = NULL;
./fs/exec.c:1199: sig->group_exit_task = NULL;
./tags:1587116:group_exit_task include/linux/sched.h /^ struct task_struct *group_exit_task;$/;" m struct:signal_struct t