Date: Mon, 11 Oct 2010 11:13:30 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org Cc: Ed Schouten <ed@80386.nl>, delphij@freebsd.org Subject: Re: truss calls setpgid() Message-ID: <201010111113.30648.jhb@freebsd.org> In-Reply-To: <20101011131719.GA90530@hoeg.nl> References: <20101011131719.GA90530@hoeg.nl>
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On Monday, October 11, 2010 9:17:19 am Ed Schouten wrote:
> Hi all,
>
> I've been seeing this bug for a very long time, but I was too lazy to
> figure out the root cause earlier. It is TTY related, but in this case
> the TTY layer is not to blame. It does things correctly.
>
> When you run a command in truss which calls ioctls on TTYs, it just
> locks up. This is because truss runs jobs in a separate process group.
> This also means you cannot send signals to it:
>
> truss sleep 10000
>
> Pressing ^C here won't work.
>
> I've fixed it locally like this:
>
> Index: usr.bin/truss/setup.c
> ===================================================================
> --- usr.bin/truss/setup.c (revision 213113)
> +++ usr.bin/truss/setup.c (working copy)
> @@ -78,7 +78,6 @@
> }
> if (pid == 0) { /* Child */
> ptrace(PT_TRACE_ME, 0, 0, 0);
> - setpgid (0, 0);
> execvp(command[0], command);
> err(1, "execvp %s", command[0]);
>
> Question: was this intentional? I'd rather not break stuff.
It was added in the switch from procfs to ptrace(), but it's not clear why the
child has a new process group. It doesn't look like truss ever tries to kill
the entire group for example.
--
John Baldwin
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