Date: Fri, 2 Sep 2005 14:37:30 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: jhb@FreeBSD.org Cc: freebsd-current@FreeBSD.org, rwatson@FreeBSD.org, current@FreeBSD.org Subject: Re: Witness patch Message-ID: <200509022137.j82LbUj2024170@gw.catspoiler.org> In-Reply-To: <200509021440.13022.jhb@FreeBSD.org>
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On 2 Sep, John Baldwin wrote: > On Thursday 01 September 2005 11:52 pm, Don Lewis wrote: >> On 1 Sep, John Baldwin wrote: >> > This patch forces witness to complain if any mutex is held when Giant is >> > locked to enforce Giant being the first mutex in the lock order. This >> > might help track down some of the network LORs being reported recently. >> > >> > http://www.FreeBSD.org/~jhb/patches/witness.patch >> >> I think it would make sense to print different messages for the >> different trigger conditions. > > Hmm, I guess I view them as all just being reversals, and that we have some > implicit orders that go something like this: > > sleepable locks --> Giant --> non-sleepable locks --> spin locks Attempting to lock one one of the other lock types while holding a spin lock already prints a unique message and results in a panic. Identifying the other cases of incorrect lock type ordering with a unique warning message eliminates the need to grovel through the source code just to find the types of the locks, and it indicates that looking at the output of "show witness" is not needed.
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