Date: Thu, 25 Aug 2011 23:56:11 +0200 From: Kip Macy <kip.macy@gmail.com> To: Charlie Martin <crmartin@sgi.com> Cc: freebsd-hackers@freebsd.org Subject: Re: Where to ask about a 7.2 bug, and debugging sys/queue.h errors Message-ID: <CAJ7_N2iRaJ9%2BSFf%2BuujbtNJ97K=L_AdP6kYoxfwFij4CY%2Bwrgg@mail.gmail.com> In-Reply-To: <4E56BB99.6030706@sgi.com> References: <4E56BB99.6030706@sgi.com>
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On Thu, Aug 25, 2011 at 11:16 PM, Charlie Martin <crmartin@sgi.com> wrote: > We're having a crash in some internal code running on FreeBSD 7.2 > (specifically =A07.2-PRERELEASE FreeBSD 7.2-PRERELEASE and yeah, I know i= t's > quite a bit behind) in which after 18-30 hours of running load tests, the > code panics with: > > panic: Bad link elm 0xffffff0044c09600 next->prev !=3D elm > cpuid =3D 0 > KDB: stack backtrace: > db_trace_self_wrapper() at 0xffffffff8019119a =3D db_trace_self_wrapper+0= x2a > panic() at 0xffffffff80307c72 =3D panic+0x182 > devfs_populate_loop() at 0xffffffff802a43a8 =3D devfs_populate_loop+0x548 > > > First question: where's the most appropriate place to ask about this kind= of > bug on a back version. Probably -stable. I don't know how many developers are still running 7. Most are on 8 at this point. > Second: does this remind anyone of any bugs? =A0Googling came up with a f= ew > somewhat similar things but hasn't provided much insight so far. This panic is very common when list updates aren't adequately serialized. > Third: I tried compiling with the sys/queue.h QUEUE_MACRO_DEBUG defined i= n > order to get more useful information from the panic. =A0The kernel build = fails > in pmap.c when this macro is defined, giving an error saying the CTASSERT > macro is resolving to a negative array size. =A0Is there any particular s= ecret > to using this macro (like, no one goes there any more?) This is because you are running amd64 and the the pv_entry constants were defined assuming the default (smaller) list entry structure. I once fixed this in a local tree, but I think I was so dismayed at the "obviousness" of the bug I was tracking down that I neglected to commit the pmap update. It shouldn't be too hard to calculate the correct constants. Cheers
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