如何查看按进程在当前时间执行的系统调用？

Question

Linux实用程序“strace”显示strace运行后启动的系统调用列表。我如何看到按流程在当前运行的系统调用？ strace开始之前。

Answer 1

proc提供什么内核目前正在做 “为” 过程的一些信息
/proc/${pid}/syscall /proc/${pid}/stack

的更多信息：

• http://man7.org/linux/man-pages/man5/proc.5.html
• http://blog.tanelpoder.com/2013/02/21/peeking-into-linux-kernel-land-using-proc-filesystem-for-quickndirty-troubleshooting/

Answer 2

你发现使用ps：

ps -p PID_OF_PROC -ocmd,stat,wchan 

wchan是这里的关键。从man ps：

WCHAN WCHAN内核函数中的过程中处于睡眠状态，一个名“ - ”如果正在运行的进程，或 “*”，如果进程是多线程和ps不显示线程。

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PROCESS状态代码 这里有不同的值，该S，STAT和状态输出说明符（标头“STAT”或“S”）将显示描述 的状态过程：

  D uninterruptible sleep (usually IO) 
      R running or runnable (on run queue) 
      S interruptible sleep (waiting for an event to complete) 
      T stopped by job control signal 
      t stopped by debugger during the tracing 
      W paging (not valid since the 2.6.xx kernel) 
      X dead (should never be seen) 
      Z defunct ("zombie") process, terminated but not reaped by its parent 

    For BSD formats and when the stat keyword is used, additional characters may be displayed: 

      < high-priority (not nice to other users) 
      N low-priority (nice to other users) 
      L has pages locked into memory (for real-time and custom IO) 
      s is a session leader 
      l is multi-threaded (using CLONE_THREAD, like NPTL pthreads do) 
      + is in the foreground process group