linux-kernel - Re: [tip:timers/urgent] hrtimer: Fix /proc/timer

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Message-ID: <20091119072040.GA23579@elte.hu>
Date:	Thu, 19 Nov 2009 08:20:40 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, heiko.carstens@...ibm.com,
	tglx@...utronix.de, feng.tang@...el.com,
	Frédéric Weisbecker 
	<fweisbec@...il.com>, Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:timers/urgent] hrtimer: Fix /proc/timer_list regression


* tip-bot for Feng Tang <feng.tang@...el.com> wrote:

> Commit-ID:  887a29f59b93cf54e21814869a4ab6e80b6fa623
> Gitweb:     http://git.kernel.org/tip/887a29f59b93cf54e21814869a4ab6e80b6fa623
> Author:     Feng Tang <feng.tang@...el.com>
> AuthorDate: Thu, 3 Sep 2009 16:32:53 +0800
> Committer:  Thomas Gleixner <tglx@...utronix.de>
> CommitDate: Wed, 18 Nov 2009 21:20:37 +0100
> 
> hrtimer: Fix /proc/timer_list regression
> 
> commit 507e1231 (timer stats: Optimize by adding quick check to avoid
> function calls) introduced a regression in /proc/timer_list.
> 
> /proc/timer_list shows now
>  #0: <c27d46b0>, tick_sched_timer, S:01, <(null)>, /-1
> instead of
>  #0: <c27d46b0>, tick_sched_timer, S:01, hrtimer_start, swapper/0
> 
> Revert the hrtimer quick check for now. The optimization needs more
> thought, but this is neither 2.6.32-rc7 nor stable material.
> 
> [ tglx: Removed unrelated changes from the original patch and massaged
>   	the changelog ]
> 
> Signed-off-by: Feng Tang <feng.tang@...el.com>
> LKML-Reference: <alpine.LFD.2.00.0911181933540.24119@...alhost.localdomain>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: stable@...nel.org
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

-tip testing found that this commit is causing boot crashes:

[...]
calling  init_mmio_trace+0x0/0xf @ 1
initcall init_mmio_trace+0x0/0xf returned 0 after 699 usecs
calling  init_graph_trace+0x0/0x29 @ 1
Testing tracer function_graph: 
------------[ cut here ]------------
------------[ cut here ]------------
WARNING: at kernel/trace/trace_functions_graph.c:131 ftrace_return_to_handler+0x119/0x130()
Hardware name: System Product Name
Bad frame pointer: expected be04be80, received be04becc
  from func timer_stats_update_stats return to 8106c6fc
Modules linked in:
Pid: 534, comm: kstop/0 Not tainted 2.6.32-rc7-00032-g887a29f-dirty #2762
Call Trace:
 [<8104681f>] warn_slowpath_common+0x5f/0x90
 [<810c1f79>] ? ftrace_return_to_handler+0x119/0x130
 [<81046899>] warn_slowpath_fmt+0x29/0x30
 [<810c1f79>] ftrace_return_to_handler+0x119/0x130
 [<81077214>] ? timer_stats_update_stats+0x14/0x200
 [<8106c6fc>] ? __run_hrtimer+0x14c/0x190
 [<8106bdb0>] ? enqueue_hrtimer+0x80/0xd0
 [<8106c657>] ? __run_hrtimer+0xa7/0x190
 [<81004842>] return_to_handler+0xc/0x3a
 [<81098700>] ? stop_cpu+0x0/0x110
 [<81004836>] return_to_handler+0x0/0x3a
 [<8106c6fc>] __run_hrtimer+0x14c/0x190
 [<81004836>] return_to_handler+0x0/0x3a
 [<8106c9e0>] hrtimer_interrupt+0x140/0x240
 [<81098700>] ? stop_cpu+0x0/0x110
 [<810987b1>] ? stop_cpu+0xb1/0x110
 [<8106392f>] worker_thread+0x15f/0x2c0
 [<810638f3>] ? worker_thread+0x123/0x2c0
 [<81068960>] ? autoremove_wake_function+0x0/0x40
 [<810637d0>] ? worker_thread+0x0/0x2c0
 [<810686ec>] kthread+0x6c/0x70
 [<81068680>] ? kthread+0x0/0x70



i've bisected back to it:

| 887a29f59b93cf54e21814869a4ab6e80b6fa623 is the first bad commit
| commit 887a29f59b93cf54e21814869a4ab6e80b6fa623
| Author: Feng Tang <feng.tang@...el.com>
| Date:   Thu Sep 3 16:32:53 2009 +0800
|
|    hrtimer: Fix /proc/timer_list regression

Config attached.

I've removed it from timers/urgent for now.

	Ingo

View attachment "config" of type "text/plain" (68930 bytes)