linux-kernel - Re: [PATCH] Mark thread stack correctly in proc/<pid>/maps

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Message-Id: <201202241112.46337.vapier@gentoo.org>
Date:	Fri, 24 Feb 2012 11:12:43 -0500
From:	Mike Frysinger <vapier@...too.org>
To:	Siddhesh Poyarekar <siddhesh.poyarekar@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, Jamie Lokier <jamie@...reable.org>
Subject: Re: [PATCH] Mark thread stack correctly in proc/<pid>/maps

On Friday 24 February 2012 00:47:48 Siddhesh Poyarekar wrote:
> On Fri, Feb 24, 2012 at 5:17 AM, Mike Frysinger wrote:
> > i don't suppose we could have it say "[tid stack]" rather than "[stack]"
> > ?  or perhaps even "[stack tid:%u]" with replacing %u with the tid ?
> 
> Why do we need to differentiate a thread stack from a process stack?

if it's trivial to display, it'd be nice to coordinate things when 
investigating issues

> If someone really wants to know, the main stack is the last one since
> it doesn't look like mmap allocates anything above the stack right
> now.

you can't rely on that.  you're describing arch-specific details that happen to 
work.

> I like the idea of marking all stack vmas with their task ids but it
> will most likely break procps.

how ?

> Besides, I think it could be done within procps with this change rather than
> having the kernel do it.

how exactly is procps supposed to figure this out ?  /proc/<pid>/maps shows the 
pid's main stack, as does /proc/<pid>/tid/*/maps.
-mike

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