linux内核读书笔记（进程终止函数分析）三

do_exit() Function
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kernel/exit.c
707 NORET_TYPE void do_exit(long code)
708 {
709 struct task_struct *tsk = current;
710
711 if (unlikely(in_interrupt()))
712 panic("Aiee, killing interrupt handler!");
713 if (unlikely(!tsk->pid))
714 panic("Attempted to kill the idle task!");
715 if (unlikely(tsk->pid == 1))
716 panic("Attempted to kill init!");
717 if (tsk->io_context)
718 exit_io_context();
719 tsk->flags |= PF_EXITING;
720 del_timer_sync(&tsk->real_timer);
721
722 if (unlikely(in_atomic()))
723 printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
724 current->comm, current->pid,
725 preempt_count());
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Line 707参数code是进城返回给父进程的退出码 Lines 711716 确保目前进程不是一个中断处理进程，确保不是idle进程（PID=0）或者是init进程（PID=1），init进程只有系统被终止时才能退出； Line 719 将该进程的flags域设置为PF_EXITING，这表明当前进程被终止； -----------------------------------------------------------------------
kernel/exit.c
...
727 profile_exit_task(tsk);
728
729 if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
730 current->ptrace_message = code;
731 ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
732 }
733
734 acct_process(code);
735 __exit_mm(tsk);
736
737 exit_sem(tsk);
738 __exit_files(tsk);
739 __exit_fs(tsk);
740 exit_namespace(tsk);
741 exit_thread();
...
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Lines 729732 如果进程被ptraced而且PT_TRACE_EXIT 被设置，我们将exit_code作为消息通知父进程 Lines 735742 将进程中不用的资源clean up掉，__exit_mm()用于释放分配给进程的内存，和释放和此进程相关的mm_struct，exit_sem()将此任务从IPC中分离，__exit_files() 释放分配给任务的文件，并且将其标识符减去，_