linux-kernel - Re: [PATCH] update fix X86_64 procfs provide stack information for threads

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Message-ID: <874opaa68v.fsf@basil.nowhere.org>
Date:	Wed, 04 Nov 2009 12:17:52 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Stefani Seibold <stefani@...bold.net>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Americo Wang <xiyou.wangcong@...il.com>
Subject: Re: [PATCH] update fix X86_64 procfs provide stack information for threads

Stefani Seibold <stefani@...bold.net> writes:
>  
> +#ifdef CONFIG_IA32_EMULATION
> +unsigned long KSTK_ESP(struct task_struct *task)
> +{
> +	return (test_tsk_thread_flag(task, TIF_IA32)) ? \
> +			(task_pt_regs(task)->sp) : \
> +			((task)->thread.usersp);

Usersp is only set for system calls, but not when the process is blocked
in a interrupt.

In general if you really want a reliable implementation of this
you would really need to stop the task and grab the stack pointer;
otherwise it can be arbitarily outdated anyways.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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