Date: Thu, 09 May 2013 15:28:13 -0700 From: Alfred Perlstein <bright@mu.org> To: attilio@FreeBSD.org Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, Marcel Moolenaar <marcel@freebsd.org>, src-committers@freebsd.org, Marcel Moolenaar <marcel@xcllnt.net> Subject: Re: svn commit: r250411 - in head/sys: conf kern sys Message-ID: <518C22FD.3020902@mu.org> In-Reply-To: <CAJ-FndAnfXXbgYxJk=v1wtLHPqmbAHnLsxtdFY8Ae3_P3dd4zA@mail.gmail.com> References: <201305091628.r49GSI33039873@svn.freebsd.org> <CAJ-FndBY%2ByuUdvO4zP3kf2W4gDvB-uih19bqdmkFW3E4NcrHtw@mail.gmail.com> <CC06FD75-868C-40B3-9C10-D66B56327803@xcllnt.net> <CAJ-FndAnfXXbgYxJk=v1wtLHPqmbAHnLsxtdFY8Ae3_P3dd4zA@mail.gmail.com>
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On 5/9/13 3:13 PM, Attilio Rao wrote: > On Thu, May 9, 2013 at 10:56 PM, Marcel Moolenaar <marcel@xcllnt.net> wrote: >> On May 9, 2013, at 9:46 AM, Attilio Rao <attilio@freebsd.org> wrote: >> >>> On Thu, May 9, 2013 at 6:28 PM, Marcel Moolenaar <marcel@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. This should be taken offline. Marcel has some needs which without such a change are hard to manage I encourage you to assist him and meeting half-way on this as it will greatly help the project. Please discuss this offline a bit so you can see where each are coming from. If you would like to cc me about this I can help mediate and explain this pragmatic approach to assertions. Will you both be at BSDCan? That would be even better. -Alfred
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