Shell – How to kill a particular thread of a process

killmultithreadingprocessshellthread

$ ps -e -T | grep myp | grep -v grep
  797   797 ?        00:00:00 myp
  797   798 ?        00:00:00 myp
  797   799 ?        00:00:00 myp
  797   800 ?        00:00:00 myp

This shows the process myp with PID = 797 and four threads with different SPIDs.

How can I kill a particular thread of the process without killing the whole process. I understand that it might not be possible at all in some cases when there are fatal dependencies on that particular thread. But, is it possible in any case? Is yes, how?

I tried kill 799 and the process itself was terminated. Now I am not sure this was because there were dependencies that made myp fail without the process 800 or because kill is simple not able to kill individual processes.

Best Answer

Threads are an integral part of the process and cannot be killed outside it. There is the pthread_kill function but it only applies in the context of the thread itself. From the docs at the link:

Note that pthread_kill() only causes the signal to be handled in the context of the given thread; the signal action (termination or stopping) affects the process as a whole.

Related Solutions

Process – How to Kill Both Process and Subprocess

There is a standard method, if the programs cooperate. Run kill -- -42 where 42 is the pid of the parent process. This sends a signal to all the processes in the process group lead by process 42 (the minus sign before the pid means process group).

Normally, if you run your python script from a shell prompt and it simply forks gnuchess, the two processes should remain in the same process group. But this doesn't seem to be the case, since Ctrl+C sends SIGINT to the whole foreground process group.

Gnuchess might be in its own process group because it made itself a session leader (but I don't know why it would do this), or because you've double-forked it (python forks a shell which forks gnuchess). A double fork is probably avoidable, but I can't tell you how without seeing your code.

A reasonably reliable and POSIX-compliant way of finding the pid of the gnuchess process is

gnuchess_pids=$(ps -A -o pid= -o cmd= | awk '$2 ~ /(^|\/)gnuchess$/ {print $1}')

Specific unix variants may have better ways of achieving this, such as pgrep.

Linux – How to renice all threads (and children) of one process on Linux

You can use /proc/$PID/task to find all threads of a given process, therefore you can use

$ ls /proc/$PID/task | xargs renice $PRIO

to renice all threads belonging to a given process.

Same way /proc/$PID/task/$PID/children can be used to find all child processes (or /proc/$PID/task/*/children if you want all child processes of all threads of a given process).

$ cat /proc/$PID/task/$PID/children | xargs renice $PRIO
$ cat /proc/$PID/task/*/children | xargs renice $PRIO

Best Answer

Related Solutions

Process – How to Kill Both Process and Subprocess

Linux – How to renice all threads (and children) of one process on Linux

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