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SubjectRe: Kernel boot hangs on commit "switch fput to task_work_add"
On Sat, Jul 14, 2012 at 02:05:10PM +0100, Al Viro wrote:
> On Tue, Jul 10, 2012 at 10:18:30PM +0800, wfg@linux.intel.com wrote:
> > Hi Al,
> >
> > The linux-next kernel reliably hung after this line:
> >
> > [ 4.846260] debug: unmapping init [mem 0xffff88000182a000-0xffff8800019fffff]
> >
> > And it's bisected to commit:
> >
> > commit 4a9ffe81385c2af04f296bea05482f34e02ea10d
> > Author: Al Viro <viro@zeniv.linux.org.uk>
> > Date: Sun Jun 24 09:56:45 2012 +0400
> >
> > switch fput to task_work_add
> >
> > ... and schedule_work() for interrupt/kernel_thread callers
> > (and yes, now it *is* OK to call from interrupt).
> >
> > I tried add this debug aid:
> >
> > init_post(void):
> > + printk(KERN_WARNING "flush_delayed_fput\n");
> > flush_delayed_fput();
> > + printk(KERN_WARNING "flush_delayed_fput done\n");
> >
> > And then it hangs after "flush_delayed_fput done". So it's not directly
> > freezing inside flush_delayed_fput()..
>
> Could you post a stack trace, etc.? I'll try to reproduce that one, obviously,
> but...

Yeah, I'm wondering (and will try) if it will help sending SYSRQ into
kvm guest. It's rather clueless without a back trace..

Thanks,
Fengguang


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