linux-kernel - Re: [patch] procfs: provide stack information for threads

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Message-ID: <m2eipl7axx.fsf@igel.home>
Date:	Fri, 02 Oct 2009 23:17:14 +0200
From:	Andreas Schwab <schwab@...ux-m68k.org>
To:	Stefani Seibold <stefani@...bold.net>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch] procfs: provide stack information for threads

Stefani Seibold <stefani@...bold.net> writes:

> This is the newest version of the formaly named "detailed stack info"
> patch which give you a better overview of the userland application stack
> usage, especially for embedded linux.
>
> Currently you are only able to dump the main process/thread stack usage
> which is showed in /proc/pid/status by the "VmStk" Value. But you get no
> information about the consumed stack memory of the the threads.
>
> There is an enhancement in the /proc/<pid>/{task/*,}/*maps and which
> marks the vm mapping where the thread stack pointer reside with "[thread
> stack xxxxxxxx]". xxxxxxxx is the start address of the stack.
>
> Also there is a new entry "stack usage" in /proc/<pid>/{task/*,}/status
> which will you give the current stack usage in kb.
>
> I also fixed stack base address in /proc/<pid>/task/*/stat to the base
> address of the associated thread stack and not the one of the main
> process. This makes more sense.

That does not work right.  I sometimes get meaningless values printed
for the stack usage in /proc/*/status (like 18014398509480456 kB), and
the stack start in /proc/*/stat is wrong.  Apparently task->stack_start
contains the stack start of the _parent_ process.

$ awk '{printf "%x\n", $28}' /proc/self/stat; grep stack /proc/self/maps /proc/$$/maps
ffd34990
/proc/self/maps:ffa9c000-ffab1000 rw-p 00000000 00:00 0                                  [stack]
/proc/4054/maps:ffd22000-ffd37000 rw-p 00000000 00:00 0                                  [stack]

Andreas.

-- 
Andreas Schwab, schwab@...ux-m68k.org
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