linux-kernel - Re: [patch 20/24] perfmon: system calls interface

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Message-ID: <20081126120215.GU6703@one.firstfloor.org>
Date:	Wed, 26 Nov 2008 13:02:15 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	eranian@...glemail.com
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mingo@...e.hu, x86@...nel.org, andi@...stfloor.org,
	eranian@...il.com, sfr@...b.auug.org.au
Subject: Re: [patch 20/24] perfmon: system calls interface

> +static int pfm_task_incompatible(struct pfm_context *ctx,
> +				 struct task_struct *task)
> +{
> +	/*
> +	 * cannot attach to a kernel thread
> +	 */
> +	if (!task->mm) {
> +		PFM_DBG("cannot attach to kernel thread [%d]", task->pid);
> +		return -EPERM;
> +	}

Check for init_mm too?

> +
> +	/*
> +	 * cannot attach to a zombie task
> +	 */
> +	if (task->exit_state == EXIT_ZOMBIE || task->exit_state == EXIT_DEAD) {
> +		PFM_DBG("cannot attach to zombie/dead task [%d]", task->pid);
> +		return -EBUSY;
> +	}

This happens unlocked doesn't it? Couldn't the state change in parallel?

-Andi
-- 
ak@...ux.intel.com
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