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Date: Tue, 02 Nov 2004 21:45:40 -0600
From: "K.R. Foley" <kr@cybsft.com>
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To: Fernando Pablo Lopez-Lezcano <nando@ccrma.Stanford.EDU>
CC: Ingo Molnar <mingo@elte.hu>, Mark_H_Johnson@raytheon.com,
       Thomas Gleixner <tglx@linutronix.de>,
       Florian Schmidt <mista.tapas@gmx.net>,
       Lee Revell <rlrevell@joe-job.com>,
       Paul Davis <paul@linuxaudiosystems.com>,
       LKML <linux-kernel@vger.kernel.org>, Bill Huey <bhuey@lnxw.com>,
       Adam Heath <doogie@debian.org>,
       Michal Schmidt <xschmi00@stud.feec.vutbr.cz>,
       Karsten Wiese <annabellesgarden@yahoo.de>,
       Rui Nuno Capela <rncbc@rncbc.org>
Subject: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.6.8
References: <OFB38B3DE8.983DDEAD-ON86256F40.0062F170-86256F40.0062F1A5@raytheon.com>	 <20041102191858.GB1216@elte.hu>  <20041102192709.GA1674@elte.hu> <1099450468.19451.260.camel@cmn37.stanford.edu>
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Fernando Pablo Lopez-Lezcano wrote:
> On Tue, 2004-11-02 at 11:27, Ingo Molnar wrote:
> 
>>* Ingo Molnar <mingo@elte.hu> wrote:
>>
>>>>This build appears to run OK and then in the middle of the real time
>>>>tests stops doing useful work (during network test).
>>>
>>>weird, the deadlock detector did not trigger, although it is a clear
>>>circular deadlock:
>>
>>ah ... found it - a fair portion of spinlocks and rwlocks had deadlock
>>detection turned off in -V0.6.6 - amongst them ptype_lock. I've uploaded
>>-V0.6.9 that fixes this.
> 
> 
> This happens with V0.6.9 running on an Athlon64:
> 
> r8169 Gigabit Ethernet driver 1.6LK loaded
> ACPI: PCI interrupt 0000:00:0b.0[A] -> GSI 16 (level, low) -> IRQ 16
> divert: allocating divert_blk for eth0
> eth0: Identified chip type is 'RTL8169s/8110s'.
> eth0: RTL8169 at 0xf88a0f00, 00:0c:76:b3:c2:43, IRQ 16
> BUG: atomic counter underflow at:
>  [<c0108153>] dump_stack+0x23/0x30 (20)
>  [<c02f5e91>] qdisc_destroy+0xe1/0xf0 (28)
>  [<c02f60ad>] dev_shutdown+0x3d/0xa0 (28)
>  [<c02e6ffb>] unregister_netdevice+0x12b/0x2a0 (36)
>  [<c0273ffe>] unregister_netdev+0x1e/0x30 (16)
>  [<f8b0b8b5>] rtl8169_remove_one+0x25/0x50 [r8169] (32)
>  [<c01f55a6>] pci_device_remove+0x76/0x80 (24)
>  [<c025f15d>] device_release_driver+0x6d/0x70 (24)
>  [<c025f18b>] driver_detach+0x2b/0x40 (20)
>  [<c025f5ff>] bus_remove_driver+0x3f/0x70 (20)
>  [<c025fb0c>] driver_unregister+0x1c/0x30 (16)
>  [<c01f586c>] pci_unregister_driver+0x1c/0x30 (16)
>  [<f8b0d357>] rtl8169_cleanup_module+0x17/0x1b [r8169] (12)
>  [<c013fdb1>] sys_delete_module+0x121/0x150 (96)
>  [<c010729d>] sysenter_past_esp+0x52/0x71 (-8124)
> ---------------------------
> | preempt count: 00000001 ]
> | 1-level deep critical section nesting:
> ----------------------------------------
> .. [<c013dc3d>] .... print_traces+0x1d/0x60
> .....[<c0108153>] ..   ( <= dump_stack+0x23/0x30)
>                                                                                 
> divert: freeing divert_blk for eth0
> ip_tables: (C) 2000-2002 Netfilter core team
> 
> -- Fernando
> 
> 
> 
Several of us get this. I believe this bug exists in upstream kernels 
also, it just doesn't get caught without the detection Ingo has added.

kr
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