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Date: Thu, 7 Dec 2006 21:49:42 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Andrew Morton <akpm@osdl.org>
Cc: Alan <alan@lxorguk.ukuu.org.uk>, Len Brown <lenb@kernel.org>,
       linux-kernel@vger.kernel.org, ak@suse.de,
       Linus Torvalds <torvalds@osdl.org>
Subject: Re: [patch] x86_64: do not enable the NMI watchdog by default
Message-ID: <20061207204942.GA20524@elte.hu>
References: <20061206223025.GA17227@elte.hu> <200612061857.30248.len.brown@intel.com> <20061207121135.GA15529@elte.hu> <20061207123011.4b723788@localhost.localdomain> <20061207123836.213c3214.akpm@osdl.org> <20061207204745.GC13327@elte.hu>
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* Ingo Molnar <mingo@elte.hu> wrote:

> > (the patch doesn't vaguely apply btw).
> 
> patch below should apply to tail of current-ish -mm. Build and boot 
> tested on x86_64.

btw., lockdep noticed a locking breakage in netconsole, see the log 
below. My guess: dev_watchdog shouldnt be taking the lock without _bh.

	Ingo

--------------->
Calling initcall 0xffffffff8098f2e0: rtl8139_init_module+0x0/0x14()
8139too Fast Ethernet driver 0.9.28
ACPI: PCI Interrupt Link [APC2] enabled at IRQ 17
IOAPIC[0]: Set PCI routing entry (2-17 -> 0x59 -> IRQ 17 Mode:1 Active:1)
ACPI: PCI Interrupt 0000:05:07.0[A] -> Link [APC2] -> GSI 17 (level, low) -> IRQ 17
eth0: RealTek RTL8139 at 0xa000, 00:c0:df:03:68:5d, IRQ 17
eth0:  Identified 8139 chip type 'RTL-8139B'
Calling initcall 0xffffffff803ce560: init_netconsole+0x0/0x68()
netconsole: device eth0 not up yet, forcing it
eth0: link up, 100Mbps, full-duplex, lpa 0xC5E1
netconsole: carrier detect appears untrustworthy, waiting 4 seconds

=================================
[ INFO: inconsistent lock state ]
2.6.19-mm1 #4
---------------------------------
inconsistent {softirq-on-W} -> {in-softirq-W} usage.
swapper/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
 (&dev->_xmit_lock){-+..}, at: [<ffffffff80453151>] dev_watchdog+0x15/0xe0
{softirq-on-W} state was registered at:
  [<ffffffff80251078>] mark_lock+0x78/0x3cf
  [<ffffffff80251422>] mark_held_locks+0x53/0x71
  [<ffffffff802515ed>] trace_hardirqs_on+0x113/0x137
  [<ffffffff803cda5f>] rtl8139_poll+0x3c9/0x3ee
  [<ffffffff8044f03d>] netpoll_poll+0xa1/0x32f
  [<ffffffff8044ef44>] netpoll_send_skb+0xdf/0x137
  [<ffffffff8044f5b4>] netpoll_send_udp+0x263/0x270
  [<ffffffff803ce632>] write_msg+0x4c/0x7e
  [<ffffffff8023671b>] __call_console_drivers+0x5f/0x70
  [<ffffffff80236790>] _call_console_drivers+0x64/0x68
  [<ffffffff80236e6c>] release_console_sem+0x148/0x207
  [<ffffffff80237165>] register_console+0x1b1/0x1ba
  [<ffffffff803ce5b4>] init_netconsole+0x54/0x68
  [<ffffffff802071d9>] init+0x178/0x347
  [<ffffffff8020ab98>] child_rip+0xa/0x12
  [<ffffffffffffffff>] 0xffffffffffffffff
irq event stamp: 23912
hardirqs last  enabled at (23912): [<ffffffff804aedc5>] _spin_unlock_irq+0x28/0x52
hardirqs last disabled at (23911): [<ffffffff804aecec>] _spin_lock_irq+0xf/0x3e
softirqs last  enabled at (23896): [<ffffffff8023befd>] __do_softirq+0xdb/0xe4
softirqs last disabled at (23909): [<ffffffff8020af0c>] call_softirq+0x1c/0x30

other info that might help us debug this:
no locks held by swapper/0.

stack backtrace:

Call Trace:
 [<ffffffff8020b304>] dump_trace+0xc1/0x3eb
 [<ffffffff8020b667>] show_trace+0x39/0x57
 [<ffffffff8020b89c>] dump_stack+0x13/0x15
 [<ffffffff80250cff>] print_usage_bug+0x26b/0x27a
 [<ffffffff8025112b>] mark_lock+0x12b/0x3cf
 [<ffffffff80251b0b>] __lock_acquire+0x3c0/0xa0f
 [<ffffffff80252426>] lock_acquire+0x4d/0x67
 [<ffffffff804ae747>] _spin_lock+0x2c/0x38
 [<ffffffff80453151>] dev_watchdog+0x15/0xe0
 [<ffffffff802401d9>] run_timer_softirq+0x167/0x1db
 [<ffffffff8023be84>] __do_softirq+0x62/0xe4
 [<ffffffff8020af0c>] call_softirq+0x1c/0x30
 [<ffffffff8020c6a2>] do_softirq+0x36/0x9c
 [<ffffffff8023bb47>] irq_exit+0x45/0x51
 [<ffffffff80219d79>] smp_apic_timer_interrupt+0x49/0x5c
 [<ffffffff8020a9bb>] apic_timer_interrupt+0x6b/0x70
 [<ffffffff80208823>] default_idle+0x36/0x50
 [<ffffffff802088d8>] cpu_idle+0x9b/0xd4
 [<ffffffff802193f9>] start_secondary+0x498/0x4a7

netconsole: network logging started
Calling initcall 0xffffffff803ce8f4: aec62xx_ide_init+0x0/0x14()
Calling initcall 0xffffffff803cf093: ali15x3_ide_init+0x0/0x14()
Calling initcall 0xffffffff803d086b: amd74xx_ide_init+0x0/0x14()
-
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