linux-kernel - Re: [PATCH 11/16] signal: prepare for CLD

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Message-ID: <20101220162120.GA15755@redhat.com>
Date:	Mon, 20 Dec 2010 17:21:20 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	roland@...hat.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	rjw@...k.pl, jan.kratochvil@...hat.com
Subject: Re: [PATCH 11/16] signal: prepare for CLD_* notification changes

On 12/06, Tejun Heo wrote:
>
>  static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
>  {
>  	struct siginfo info;
>  	unsigned long flags;
>  	struct task_struct *parent;
>  	struct sighand_struct *sighand;
> +	struct signal_struct *sig;
> +	int notify = 0;
> +
> +	/*
> +	 * Determine whether and what to notify.  This should be done under
> +	 * @tsk's siglock.

Hmm... it is not clear why.

> +	spin_lock_irqsave(&sighand->siglock, flags);
>
> +	switch (why) {
> +	case CLD_CONTINUED:
> +	case CLD_STOPPED:
> +	case CLD_TRAPPED:
> +		notify = why;
> +		break;
> +	}

OK, with the next patches this code checks sig->flags, probably that
is why we take ->siglock. Still I can't understand this so far.
May be the comment could tell more?

> @@ -1640,6 +1684,7 @@ static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
>   	}
>
>  	sighand = parent->sighand;
> +	sig = parent->signal;

This looks unneeded.

Oleg.

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