linux-kernel - Re: [PATCH] Fix Bug messages

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Message-ID: <20080731100023.0221ec2b@bull.net>
Date:	Thu, 31 Jul 2008 10:00:23 +0200
From:	Sebastien Dugue <sebastien.dugue@...l.net>
To:	Chirag Jog <chirag@...ux.vnet.ibm.com>
Cc:	J?rgen Mell <j.mell@...nline.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	rt-users <linux-rt-users@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Clark Williams <williams@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Triplett <josht@...ux.vnet.ibm.com>,
	"Timothy R. Chavez" <tim.chavez@...ux.vnet.ibm.com>
Subject: Re: [PATCH] Fix Bug messages

On Wed, 30 Jul 2008 22:48:42 +0530 Chirag Jog <chirag@...ux.vnet.ibm.com> wrote:

> * J?rgen Mell <j.mell@...nline.de> [2008-07-30 11:01:32]:
> 
> > Hello Thomas,
> > 
> > On Wednesday, 30. July 2008, Thomas Gleixner wrote:
> > > We are pleased to announce the 2.6.26-rt1 tree, which can be
> > > downloaded from the location:
> > 
> > I have tried the new kernel and have some good news and some bad news:
> > 
> > The good news: The machine boots and seems to run without major problems.
> > 
> > The bad news: It produces continuously lots of bug messages in the error 
> > logs (cf. attached dmesg.tgz). The error at rtmutex.c:743 was already 
> > present in 2.6.25-rt* when ACPI was enabled. The 'using smp_processor_id 
> > ()  in preemptible code' is new here with 2.6.26.
> > 
> > Machine is an old Athlon XP (single core) on an EPOX mainboard with VIA 
> > chipset.
> > 
> > If I can help with testing, please let me know.
> > 
> > Bye,
> >          Jürgen
> > 
> > 
> This patch should solve some of the bug messages.
> It does two things:
> 1. Change rt_runtime_lock to be a raw spinlock as the comment above it
> says: it is nested inside the rq lock.
> 
> 2. Change mnt_writers to be a per_cpu locked variable.
> This eliminates the need for the codepath to disable preemption and
> then potentially sleep, leading to the BUG messages
> 
> Signed-Off-By: Chirag <chirag@...ux.vnet.ibm.com>

  Neat, the only remaining BUGs I see are from sock_prot_inuse_add()

BUG: using smp_processor_id() in preemptible [00000000] code: arping/1916
caller is .sock_prot_inuse_add+0x30/0x80
Call Trace:
[c0000000eed2f910] [c000000000010304] .show_stack+0x70/0x1bc (unreliable)
[c0000000eed2f9c0] [c0000000001a2340] .debug_smp_processor_id+0x138/0x168
[c0000000eed2fa70] [c0000000002181f4] .sock_prot_inuse_add+0x30/0x80
[c0000000eed2fb10] [c00000000026d96c] .udp_lib_get_port+0x2a8/0x320
[c0000000eed2fbc0] [c000000000275b30] .inet_bind+0x168/0x248
[c0000000eed2fc60] [c000000000215024] .sys_bind+0x98/0xdc
[c0000000eed2fd90] [c0000000002370bc] .compat_sys_socketcall+0xcc/0x214
[c0000000eed2fe30] [c0000000000086ac] syscall_exit+0x0/0x40
BUG: arping:1916 task might have lost a preemption check!
Call Trace:
[c0000000eed2f890] [c000000000010304] .show_stack+0x70/0x1bc (unreliable)
[c0000000eed2f940] [c00000000004e298] .preempt_enable_no_resched+0x60/0x78
[c0000000eed2f9c0] [c0000000001a2348] .debug_smp_processor_id+0x140/0x168
[c0000000eed2fa70] [c0000000002181f4] .sock_prot_inuse_add+0x30/0x80
[c0000000eed2fb10] [c00000000026d96c] .udp_lib_get_port+0x2a8/0x320
[c0000000eed2fbc0] [c000000000275b30] .inet_bind+0x168/0x248
[c0000000eed2fc60] [c000000000215024] .sys_bind+0x98/0xdc
[c0000000eed2fd90] [c0000000002370bc] .compat_sys_socketcall+0xcc/0x214
[c0000000eed2fe30] [c0000000000086ac] syscall_exit+0x0/0x40

...

  Thanks,

  Sebastien.


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