svn commit: r250411 - in head/sys: conf kern sys

[Attilio Rao]

On Thu, May 9, 2013 at 10:56 PM, Marcel Moolenaar <marcel at xcllnt.net> wrote:
>
> On May 9, 2013, at 9:46 AM, Attilio Rao <attilio at freebsd.org> wrote:
>
>> On Thu, May 9, 2013 at 6:28 PM, Marcel Moolenaar <marcel at freebsd.org> wrote:
>>> Author: marcel
>>> Date: Thu May  9 16:28:18 2013
>>> New Revision: 250411
>>> URL: http://svnweb.freebsd.org/changeset/base/250411
>>>
>>> Log:
>>>  Add option WITNESS_NO_VNODE to suppress printing LORs between VNODE
>>>  locks. To support this, VNODE locks are created with the LK_IS_VNODE
>>>  flag. This flag is propagated down using the LO_IS_VNODE flag.
>>>
>>>  Note that WITNESS still records the LOR. Only the printing and the
>>>  optional entering into the kernel debugger is bypassed with the
>>>  WITNESS_NO_VNODE option.
>>
>> This is the wrong way to deal with such problem and I avoided to do
>> something like that on purpose.
>
> I disagree. We have known LOR messages between VNODE locks that
> pollute the console and so far we haven't fixed the root cause
> in some form or shape. Silencing this known case is good to
> maximize the attention LORs need to be given while still have
> witness involved to catch locking problems with vnodes that are
> of a different nature.
>
>>
>> The way to fix this is to implement LK_NOWITNESS on a per-lock basis
>> into lockmgr, propagate the same concept to the vn_lock() (which
>> should be basically done automatically) and finally identify the
>> false-positive case and commit for them explicitely LK_NOWITNESS on a
>> per-call basis, explaining in detail why the single case reported is a
>> false-positive.
>
> This is worse. You want witness involved.
>
>> Please revert this patch asap.
>
> This change does not inhibit people from fixing the problem at the
> root cause, and in the mean time maximize witness' effectiveness.
> Calling for a backout is unwarranted and unnecessarily aggressive.

I completely disagree with the whole content of your e-mail.
Thanks for disrupting a useful tool along with other commits which
happened in the past by other people about invariants effectiveness.

Attilio


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