Date: Thu, 25 Aug 2011 17:12:09 -0500 From: Brandon Gooch <jamesbrandongooch@gmail.com> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-hackers@freebsd.org, Charlie Martin <crmartin@sgi.com> Subject: Re: Where to ask about a 7.2 bug, and debugging sys/queue.h errors Message-ID: <CALBk6yL=T5nfL3rqJtskNS3ahafr0PM-4j5hpqzk8WkK_UXJNQ@mail.gmail.com> In-Reply-To: <20110825215348.GW17489@deviant.kiev.zoral.com.ua> References: <4E56BB99.6030706@sgi.com> <20110825215348.GW17489@deviant.kiev.zoral.com.ua>
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On Thu, Aug 25, 2011 at 4:53 PM, Kostik Belousov <kostikbel@gmail.com> wrot= e: > On Thu, Aug 25, 2011 at 03:16:09PM -0600, Charlie Martin 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 >> it'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+= 0x2a >> panic() at 0xffffffff80307c72 =3D panic+0x182 >> devfs_populate_loop() at 0xffffffff802a43a8 =3D devfs_populate_loop+0x54= 8 >> >> >> First question: where's the most appropriate place to ask about this >> kind of bug on a back version. > It is fine to ask there. > >> >> Second: does this remind anyone of any bugs? =A0Googling came up with a >> few somewhat similar things but hasn't provided much insight so far. > In 99% of the cases, it means that you forgot to dev_ref() some cdev. So dev_ref increments the reference count for a cdev. Even though the work "loop" seems to indicate that we will iterate over a list of objects (one of which we may be missing a reference to via a missing dev_ref()), I'm not seeing how this can cause a panic from inside devfs_populate_loop(). Can you help me understand this? -Brandon
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