linux-kernel - Re: [patch] add /proc/pid/stack to dump task's stack trace

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Date:	Tue, 11 Nov 2008 14:20:18 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Marcin Slusarz <marcin.slusarz@...il.com>
Cc:	Alexey Dobriyan <adobriyan@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ken Chen <kenchen@...gle.com>, linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [patch] add /proc/pid/stack to dump task's stack trace


* Marcin Slusarz <marcin.slusarz@...il.com> wrote:

> On Fri, Nov 07, 2008 at 10:03:04AM +0100, Ingo Molnar wrote:
> > 
> > btw., the feature works beautifully:
> > 
> > task sleeping/blocked:
> > 
> >  # cat /proc/1/stack
> >  [<ffffffff802bfe75>] do_select+0x51a/0x582
> >  [<ffffffff802c0059>] core_sys_select+0x17c/0x218
> >  [<ffffffff802c0344>] sys_select+0x99/0xc1
> >  [<ffffffff8020c23b>] system_call_fastpath+0x16/0x1b
> >  [<ffffffffffffffff>] 0xffffffffffffffff
> > 
> > task running on this CPU:
> > 
> >  # cat /proc/self/stack
> >  [<ffffffff80216f79>] save_stack_trace_tsk+0x26/0x44
> >  [<ffffffff802f59a5>] proc_pid_stack+0x6e/0xd3
> >  [<ffffffff802f6da3>] proc_info_read+0x68/0xba
> >  [<ffffffff802b2f17>] vfs_read+0xa9/0xe3
> >  [<ffffffff802b301f>] sys_read+0x4c/0x73
> >  [<ffffffff8020c23b>] system_call_fastpath+0x16/0x1b
> >  [<ffffffffffffffff>] 0xffffffffffffffff
> > 
> > task running on another CPU in user-space:
> > 
> >  # cat /proc/18579/stack
> >  [<ffffffffffffffff>] 0xffffffffffffffff
> 
> so this file provides view of _kernel_ stack only?
> shouldn't it be named kernel-stack then?

it prints the kernel stack right now, but i'd not restrict it to the 
kernel stack conceptually: i think we could eventually expand it to 
print the user-space portion of the stack as well. (in the case when 
user-space is built with frame pointers) We've got code for that in 
the kernel already. It would be an easy one-stop-shop for full-range.

	Ingo
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