linux-kernel - Re: Pause a process execution from external program

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Message-ID: <CAOuPNLj4useN+BiPJvd2MRMntELt=_Kc_8x=mbxfrkgWh5v7Mw@mail.gmail.com>
Date:   Mon, 17 Jun 2019 17:50:32 +0530
From:   Pintu Agarwal <pintu.ping@...il.com>
To:     Valdis Klētnieks <valdis.kletnieks@...edu>
Cc:     Shyam Saini <mayhs11saini@...il.com>,
        open list <linux-kernel@...r.kernel.org>, pedro@...ves.net,
        Kernelnewbies <kernelnewbies@...nelnewbies.org>
Subject: Re: Pause a process execution from external program

On Fri, Jun 14, 2019 at 1:13 AM Valdis Klētnieks
<valdis.kletnieks@...edu> wrote:
>
> On Thu, 13 Jun 2019 13:22:12 +0530, Shyam Saini said:
>
> > from command line we use ctrl-z to stop execution of a foreground
> > process but you can program
> > SIGTSTP signal handler in your application code to do the same.
>
> Note that if you simply fail to include a signal handler for SIGSTOP and
> SIGCONT, it will Do The Right Thing.  The only programs that need worry about
> SIGTSTP are ones like 'vi' that may want to do something (like restore the
> terminal state from raw to cooked mode, etc) before they stop.  That's why you
> can control-z /bin/cat without it having to include a signal handler for it.
>
> % kill -STOP `pidof process-to-stop`   # stop it
> % kill -CONT `pidof process-to-stop`  # and make it run again.
>
> No source code modifications needed.  No source needed.
>
> Now, if you want to make it stop at a *specific point*, then you're into
> ptrace territory, and source will be helpful.
>
Yes, I think ptrace can serve our purpose.
Thank you so much.