linux-kernel - Re: [PATCH 4/5] ptrace: implement TRAP_NOTIFY and use it for group stop events

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Message-ID: <20110616195138.GB14786@redhat.com>
Date:	Thu, 16 Jun 2011 21:51:38 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	vda.linux@...glemail.com, jan.kratochvil@...hat.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, indan@....nu, bdonlan@...il.com,
	pedro@...esourcery.com
Subject: Re: [PATCH 4/5] ptrace: implement TRAP_NOTIFY and use it for group
	stop events

On 06/14, Tejun Heo wrote:
>
> When group stop state of a seized tracee changes, JOBCTL_TRAP_NOTIFY
> is set,

I already applied this series. But somehow I have the fuzzy feeling we
can simplify JOBCTL_TRAP_NOTIFY/JOBCTL_TRAP_STOP logic later. No, I can't
explain what I mean ;)

One question,

> @@ -1797,8 +1824,10 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
>  	if (why == CLD_STOPPED && (current->jobctl & JOBCTL_STOP_PENDING))
>  		gstop_done = task_participate_group_stop(current);
>
> -	/* any trap clears pending STOP trap */
> +	/* any trap clears pending STOP trap, STOP trap clears NOTIFY */
>  	task_clear_jobctl_pending(current, JOBCTL_TRAP_STOP);
> +	if (info && info->si_code >> 8 == PTRACE_EVENT_STOP)
> +		task_clear_jobctl_pending(current, JOBCTL_TRAP_NOTIFY);

OK, but can't we check why == CLD_STOPPED instead of PTRACE_EVENT_STOP?

In fact, can't we move all code above under 'if (why == CLD_STOPPED)' ?
JOBCTL_TRAP_STOP can't be set otherwise, no? I am almost sure I missed
something though.

Oleg.

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