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Date: Thu, 27 Feb 2014 20:32:26 +0900 (JST)
Message-Id: <20140227.203226.2191673573133476018.okuno.kohji@jp.panasonic.com>
To: hps@bitfrost.no
Subject: Re: kqueue for usb_dev
From: Kohji Okuno <okuno.kohji@jp.panasonic.com>
In-Reply-To: <530F197D.6040004@bitfrost.no>
References: <20140227.190128.1827840697797583715.okuno.kohji@jp.panasonic.com>
 <20140227.193914.1745107579233813450.okuno.kohji@jp.panasonic.com>
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Cc: jmg@funkthat.com, freebsd-current@freebsd.org, okuno.kohji@jp.panasonic.com
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Hi HPS,

Your patch did not resolve the kernel panic.
I think, we should check knlist_clear() before knlist_destroy().
When a device is lost suddenly, usb_dev notify to a process in
usb_fifo_close() and then calls knlist_destroy(). knlist_destroy()
clears knlist->kn_lock and knlist->kn_unlock.

But, the process that is notified will start over kqueue_scan() after
knlist_destroy(). And, in KN_LIST_LOCK(kn), the context will call NULL
function (kn->knlist->kn_lock).

Regards,
 Kohji Okuno

> On 02/27/14 11:39, Kohji Okuno wrote:
>> Hi HPS and John-Mark,
>>
>> After I changed as the following, the kernel panic does not happen.
>> What do you think about this change?
>>
>> +       knlist_clear(&f->selinfo.si_note, 0);
>>          knlist_destroy(&f->selinfo.si_note);
>>
>> Regards,
>>   Kohji Okuno
>>
> 
> Can you try the attached patch instead?
> 
> --HPS
>