linux-kernel - Re: futex question

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Message-ID: <20091005111933.GA25889@elte.hu>
Date:	Mon, 5 Oct 2009 13:19:33 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Anirban Sinha <ani@...rban.org>, linux-kernel@...r.kernel.org,
	Darren Hart <dvhltc@...ibm.com>,
	Kaz Kylheku <kaz@...gmasystems.com>,
	Anirban Sinha <asinha@...gmasystems.com>
Subject: Re: futex question


* Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> diff --git a/fs/exec.c b/fs/exec.c
> index d49be6b..0812ba6 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1295,6 +1295,22 @@ int do_execve(char * filename,
>  	bool clear_in_exec;
>  	int retval;
>  
> +	retval = -EWOULDBLOCK;
> +#ifdef CONFIG_FUTEX
> +	if (unlikely(current->robust_list))
> +		goto out_ret;
> +#ifdef CONFIG_COMPAT
> +	if (unlikely(current->compat_robust_list))
> +		goto out_ret;
> +#endif
> +	spin_lock_irq(&current->pi_lock);
> +	if (!list_empty(&current->pi_state_list)) {
> +		spin_unlock_irq(&current->pi_lock);
> +		goto out_ret;
> +	}
> +	spin_unlock_irq(&current->pi_lock);
> +#endif

i suspect this should have the form of:

	retval = can_exec_robust_futexes();
	if (retval)
		goto out_ret

  	retval = unshare_files(&displaced);
  	if (retval)
  		goto out_ret;

	...

but ... shouldnt we just do what exec normally does and zap any state 
that shouldnt be carried over into the new context - instead of denying 
the exec? Am i missing something?

	Ingo
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