Re: Kernel boot hangs on commit "switch fput to task_work_add"

From: Al Viro
Date: Sat Jul 14 2012 - 09:05:15 EST


On Tue, Jul 10, 2012 at 10:18:30PM +0800, wfg@xxxxxxxxxxxxxxx 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@xxxxxxxxxxxxxxxxxx>
> 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...
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