linux-kernel - Re: kobject: delayed kobject release: help find buggy drivers

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Message-ID: <20130905051945.GB23209@redhat.com>
Date:	Thu, 5 Sep 2013 01:19:45 -0400
From:	Dave Jones <davej@...hat.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	rmk+kernel@....linux.org.uk
Subject: Re: kobject: delayed kobject release: help find buggy drivers

On Wed, Sep 04, 2013 at 09:57:45PM -0700, Greg KH wrote:
 > On Thu, Sep 05, 2013 at 12:13:38AM -0400, Dave Jones wrote:
 > > On Wed, Sep 04, 2013 at 02:53:11PM +0930, Rusty Russell wrote:
 > >  
 > >  > >> With this enabled, I get a bunch of scrolling oopses immediately after
 > >  > >> exiting the bootloader. It happens so early I can't even capture them
 > >  > >> over usb-serial, or earlyprintk=dbgp.
 > >  > >> 
 > >  > >> And for whatever reason, the printk path while oopsing ignores boot_delay parameter,
 > >  > >> so I can't even use that.
 > >  > >> 
 > >  > >> any ideas ?
 > >  > >
 > >  > > The first big bug found with this was with the module kobject code, and
 > >  > > a fix for that should be going in through Rusty's tree to Linus for this
 > >  > > merge window (right Rusty?)
 > >  > 
 > >  > Yep, just sent pull request.  The fix was the final commit there...
 > > 
 > > Crap, that isn't the bug I'm hitting.
 > 
 > Any chance to get a oops traceback?

Got it. (I think I was getting tracebacks from multiple cpus, hence the spewing).
Adding a check for tainted() = infinite loop to show_backtrace() combined with boot_delay
gave me a really long oops that I had to grab video to record.

RIP: <null>

Trace:
<IRQ>
run_timer_softirq
__do_softirq
irq_exit
smp_apic_timer_interrupt
apic_timer_interrupt
<EOI>
vprintk_emit
dev_vprintk_emit
dev_vprint_emit
__dev_printk
_dev_info
ahci_print_info
ahci_init_one
local_pci_probe
pci_device_probe
driver_probe_device
__driver_attach
bus_for_each_dev
driver_attach
bus_add_driver
driver_register
__pci_register_driver
ahci_pci_driver_init
do_one_initcall
...

	Dave

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