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Date: Wed, 03 Dec 2014 21:53:20 +0800
From: Julian Elischer <julian@freebsd.org>
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To: Andriy Gapon <avg@FreeBSD.org>, Warner Losh <imp@bsdimp.com>
Subject: Re: witness and modules.
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On 12/3/14, 7:26 PM, Andriy Gapon wrote:
> On 03/12/2014 04:33, Julian Elischer wrote:
>> On 12/3/14, 12:24 AM, Warner Losh wrote:
>>>> On Dec 1, 2014, at 10:08 PM, Julian Elischer <julian@freebsd.org> wrote:
>>>>
>>>> On 12/1/14, 11:39 PM, John Baldwin wrote:
>>>>> On Friday, November 28, 2014 11:08:35 PM Julian Elischer wrote:
>>>>>> Do we need to compile all modules with witness definitions when
>>>>>> linking with a kernel compiled with witness?
>>>>>> This was true at one stage but I remember some work was done to make
>>>>>> them compatible.
>>>>> You should not need this.  modules always call functions in the kernel for
>>>>> lock operations and this functions are what invoke WITNESS.
>>>>>
>>>> that's what I thought but empirical evidence disagrees.
>>>> I'll try some more cases.
>>> I swap back and forth all the time between the two. Kernel modules don’t
>>> change when you compile them with WITNESS or without.
>> not entirely..
>> hwpmc.ko:                 U witness_restore
>> hwpmc.ko:                 U witness_save
>> zfs.ko:                 U witness_restore
>> zfs.ko:                 U witness_save
> Seems like the problem affects modules that use DROP_GIANT / PICKUP_GIANT.
>
that's a good observation. I'll take a look a that later.