Date: Fri, 31 Jul 2009 14:50:41 -0400 From: John Baldwin <jhb@freebsd.org> To: Marcel Moolenaar <xcllnt@mac.com> Cc: Anton Shterenlikht <mexas@bristol.ac.uk>, freebsd-current@freebsd.org, Alexandre Sunny Kovalenko <gaijin.k@gmail.com> Subject: Re: FreeBSD 8.0-BETA2/amd64 crashes on SMP under load Message-ID: <200907311450.41829.jhb@freebsd.org> In-Reply-To: <FB487E3B-56D3-4490-BDA8-921F0DCBD0D3@mac.com> References: <4A6DB30B.20705@zedat.fu-berlin.de> <200907311325.54104.jhb@freebsd.org> <FB487E3B-56D3-4490-BDA8-921F0DCBD0D3@mac.com>
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On Friday 31 July 2009 2:01:49 pm Marcel Moolenaar wrote: > > On Jul 31, 2009, at 10:25 AM, John Baldwin wrote: > >> In other words: kgdb was designed to hide FreeBSD specifics from the > >> core GDB > >> code, because core GDB doesn't know how to deal with all FreeBSD > >> details. > >> Revision 178670 created a stronger dependency on core GDB and as such > >> broke > >> architectures that core GDB doesn't support for FreeBSD. > > > > So gdb doesn't work for core dumps on regular processes under ia64? > > It does, but kernel core files aren't matched, because the OSABI > is standalone. Also, GDB doesn't have libkvm support for ia64, > which is probably what makes it work on i386/amd64. Regular gdb doesn't support libkvm on i386/amd64 either. > > Still, > > kgdb doesn't actually use the regular core target at all, it uses > > its own > > target that uses libkvm to service the actual memory I/O that > > normally goes > > to the core target. > > That's maybe the problom: is the kgdb target used at all? > If it were, then why did ia64 break? > > Maybe we have a simple resolution problem where GDB just > happens to pick the wrong core_stratum target on ia64... Hmm, so kgdb actually forces its own core_stratum target always via initalize_kgdb_target(). It overrides the "base" core_target that uses libbfd, etc. Thus, kgdb will always use libkvm and not libbfd for handling core files. > I haven't had the time for root cause hunting, so from here > on things should be taken with plenty of salt. I can check > PowerPC for example... I do believe it has been used on sparc64 at least since my changes. > > The previous code was very hacky and didn't allow you > > to use the 'file' and 'core' commands as a result. > > Actually it was by design. Well, that wasn't very intuitive to folks used to regular gdb. I think it now functions more like gdb in that you can switch executables or core images and modules show up as shared libraries, etc. IIRC, it was also a lot harder to add KLD/module support in the previous arrangement since I needed to override the thread_stratum for kld handling independent of having either a remote target or a vmcore target. That is probably the main reason I changed it from thread_stratum to core_stratum actually. -- John Baldwin
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