linux-kernel - Re: [regression] Latest git has WARN

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Date:	Fri, 3 Oct 2008 08:36:18 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Christian Borntraeger <borntraeger@...ibm.com>
cc:	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [regression] Latest git has WARN_ON storm with e1000e driver



On Fri, 3 Oct 2008, Christian Borntraeger wrote:
> 
> Very good point indeed. Seems my analysis was wrong. I made a short test and 
> preempt_count() returns 1 when the WARN_ON triggers. So its either a spinlock 
> or something else that increased my preempt_count.

Ok, I can repro it. I couldn't see it before because I usually don't have 
PREEMPT even enabled.  Enabling PREEMPT and PREEMPT_DEBUG gets me the 
messages too. Jesse?

The call trace is much better with frame pointers enabled, loke so (with
the '?' entries removed as stale):

   Call Trace:
	warn_on_slowpath+0x53/0x7a
	e1000_acquire_swflag_ich8lan+0x2d/0xe1
	e1000_read_nvm_ich8lan+0x4f/0xee
	e1000e_read_pba_num+0x4e/0x69
	e1000_probe+0xa32/0xb71
	pci_device_probe+0x4c/0x72
	driver_probe_device+0xc0/0x16e
	__driver_attach+0x4f/0x79
	bus_for_each_dev+0x4f/0x89
	driver_attach+0x1c/0x1e
	bus_add_driver+0xb7/0x1f4
	driver_register+0xa8/0x128
	__pci_register_driver+0x66/0x9d
	e1000_init_module+0x4f/0x6b
	_stext+0x47/0x13f
	kernel_init+0x127/0x17b
	child_rip+0xa/0x11

and yes, there's quite a lot of them.  I'm not seeing what disables
preemption, though.  I'll look at it some more, but I decided I should
post that cleaned-up call chain so that others can do so too..

		Linus

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