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I am using strace to see what certain processes are doing. I have an Apache process that seems to be running forever, taking up 97.8% of a core and almost 2GB of RAM.

Now when I run strace on this process there is no output at all. Does this mean that the process is dead and sitting in there taking up resources? Can I kill the process without worrying about doing something bad?

I am running strace in the following way:

strace -p6873

Thanks

Josh Pennington

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  • it can be another inner process running and the main one is waiting = no output. check it and try a different PID. Commented Aug 26, 2021 at 15:03

1 Answer 1

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The process seems to be stuck in a single long-running syscall. Since strace doesn't show the syscall that was running, when it attached the process, you get no output. You could maybe get more info using a debugger like gdb and running a stack trace (gdb command: bt).

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    It also might be doing internal processing; strace only sees syscalls, but not all calls are syscalls... a tight infinite loop (bug) would also just hang as above. Commented Oct 14, 2010 at 3:56
  • You're probably right, hence the high cpu usage. Commented Oct 14, 2010 at 11:16
  • "Since strace doesn't show the syscall that was running" -- I disagree; when I strace a process blocked in a syscall I see a partial line like write(1, "y\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\ny\n"..., 4096 or futex(0x7f2b3c14fe54, FUTEX_WAIT_PRIVATE, 59, NULL Commented Sep 6, 2016 at 10:03
  • No, what you do see is restart_syscall(<... resuming interrupted xyz ...>) where xyz is the syscall. See pjz's comment for the more correct explanation. Commented Sep 6, 2016 at 20:05

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