linux-kernel - Re: [PATCH 04/10] ptrace: implement PTRACE

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Message-ID: <20110518183815.GA1064@redhat.com>
Date:	Wed, 18 May 2011 20:38:15 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	jan.kratochvil@...hat.com, vda.linux@...glemail.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, indan@....nu, bdonlan@...il.com
Subject: Re: [PATCH 04/10] ptrace: implement PTRACE_INTERRUPT

On 05/16, Tejun Heo wrote:
>
> +	case PTRACE_INTERRUPT:
> +		/*
> +		 * Stop tracee without any side-effect on signal or job
> +		 * control.  At least one trap is guaranteed to happen
> +		 * after this request.  If @child is already trapped, the
> +		 * current trap is not disturbed and another trap will
> +		 * happen after the current trap is ended with PTRACE_CONT.
> +		 *
> +		 * The actual trap might not be PTRACE_EVENT_STOP trap but
> +		 * the pending condition is cleared regardless.
> +		 */
> +		if (likely(child->ptrace & PT_SEIZED) &&
> +		    lock_task_sighand(child, &flags)) {
> +			child->jobctl |= JOBCTL_TRAP_STOP;

The same race with do_signal_stop() afaics.

Otherwise looks fine to me. Compared to V1, personally I like the new
behaviour more. PTRACE_INTERRUPT and PTRACE_SEIZE do the same.

Oleg.

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