On Thu, Sep 05, 2013 at 10:44:34PM +0100, Russell King - ARM Linux wrote:
> On Thu, Sep 05, 2013 at 05:26:06PM -0400, Dave Jones wrote:
> > On Thu, Sep 05, 2013 at 05:11:13PM -0400, Dave Jones wrote:
> > > > Trying without serial console next..
> > >
> > > rebuilt with all serial turned off.
> > >
> > > no luck, then it oopses somewhere else. I'm suspecting something isn't
> > > right with that debug patch, as the next trace is also in
> > kobject_release
>
> You're right about that - I had assumed that it was necessary for all
> kobjects to be 'added' before they're released, but that is not so.
> Mea culpa. They just need to be initialised - the problem with putting
> a kmalloc into kobject_init() is that if it fails, we have no way to
> report that failure...
>
> Updated patch attached... though it sounds like you got it working
> anyway.
>
> > I managed to get to userspace on one boot, and got this.
> >
> > kobject ffff88023d93f518 has been corrupted (magic 0x6b6b6b6b). Please
> > enable kobject debugging for full debug.
>
> Okay, so this is definitely a case that someone has kfree'd the kobject
> without waiting for the ->release function to be called.
>
> > That looks like SLAB_POISON. Incompatibility between the two options ?
> >
> > For some reason, even though I have DEBUG_KOBJECT on, I didn't get
> > extra messages output.
>
> Hmm.
>
> ifeq ($(CONFIG_DEBUG_KOBJECT),y)
> CFLAGS_kobject.o += -DDEBUG
> CFLAGS_kobject_uevent.o += -DDEBUG
> endif
>
> should enable the pr_debug()'s in lib/kobject.c... which should at least
> appear in the dmesg log. Being debug level, of course, they won't appear
> during normal kernel boot unless 'debug' is passed on the kernel command
> line.
>
> It seems to work for me - but... produces rather a lot of debug messages,
> so you may also wish to ensure that you have LOG_BUF_SHIFT set to
> something large.
As discussed on irc, with this updated patch it hangs *really* early in boot.
With earlyprintk=vga I can see some of the trace..
kobject_init
firmware_map_add_entry
firmware_map_add_early
e820_reserve_resources
setup_arch
start_kernel
x86_64_start_reservations
x86_64_start_kernel
<RIP> kmem_cache_alloc_trace
Dave
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