linux-kernel - Re: [PATCH 1/1] HID: fix tty<->hid deadlock

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Message-ID: <48DCC18B.2060302@gmail.com>
Date:	Fri, 26 Sep 2008 13:03:39 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Valdis.Kletnieks@...edu
CC:	Alan Cox <alan@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] HID: fix tty<->hid deadlock

Valdis.Kletnieks@...edu napsal(a):
> On Thu, 04 Sep 2008 17:16:07 +0200, Jiri Slaby said:
> 
>> hid_compat_load() runs on the default workqueue, it request_module(), it
>> execs modprobe, it exits, tty flushes default workqueue, it hangs, because
>> we are still in it.
>>
>> I haven't run into it since there always was at least one opener of the tty,
>> I guess. Could you try the patch below?
>>
>> --
>>
>> Signed-off-by: Jiri Slaby <jirislaby@...il.com>
>> ---
>>  drivers/hid/hid-core.c |   11 ++++++++++-
>>  1 files changed, 10 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
>> index 92c16e1..18d952a 100644
>> --- a/drivers/hid/hid-core.c
>> +++ b/drivers/hid/hid-core.c
> 
> With this patch applied, the kernel behaves as expected for my config: it
> requests a 'modprobe hid_dummy', which prints a nasty message about being
> unable to find it on the initrd, and then we continue with the boot.

Thanks for testing, I can't think of any method which would solve this
problem. As this compat module is a temporary solution for those who have
(very) old module init tools (not supporting aliases), I wouldn't do
anything else until somebody complains.
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