Re: atomic changes break drm-next-kmod?

From: Johannes Lundberg <johalun0_at_gmail.com>
Date: Fri, 6 Jul 2018 10:14:01 +0100
On Fri, Jul 6, 2018 at 9:49 AM Konstantin Belousov <kostikbel_at_gmail.com>
wrote:

> On Fri, Jul 06, 2018 at 09:52:24AM +0200, Niclas Zeising wrote:
> > On 07/06/18 00:02, Warner Losh wrote:
> > >
> > >
> > > On Thu, Jul 5, 2018 at 1:44 PM, John Baldwin <jhb_at_freebsd.org
> > > <mailto:jhb_at_freebsd.org>> wrote:
> > >
> > >     On 7/5/18 12:36 PM, Konstantin Belousov wrote:
> > >      > On Thu, Jul 05, 2018 at 09:12:24PM +0200, Hans Petter Selasky
> wrote:
> > >      >> On 07/05/18 20:59, Hans Petter Selasky wrote:
> > >      >>> On 07/05/18 19:48, Pete Wright wrote:
> > >      >>>>
> > >      >>>>
> > >      >>>> On 07/05/2018 10:10, John Baldwin wrote:
> > >      >>>>> On 7/3/18 5:10 PM, Pete Wright wrote:
> > >      >>>>>>
> > >      >>>>>> On 07/03/2018 15:56, John Baldwin wrote:
> > >      >>>>>>> On 7/3/18 3:34 PM, Pete Wright wrote:
> > >      >>>>>>>> On 07/03/2018 15:29, John Baldwin wrote:
> > >      >>>>>>>>> That seems like kgdb is looking at the wrong CPU.  Can
> > >     you use
> > >      >>>>>>>>> 'info threads' and look for threads not stopped in
> > >     'sched_switch'
> > >      >>>>>>>>> and get their backtraces?  You could also just do
> 'thread
> > >     apply
> > >      >>>>>>>>> all bt' and put that file at a URL if that is easiest.
> > >      >>>>>>>>>
> > >      >>>>>>>> sure thing John - here's a gist of "thread apply all bt"
> > >      >>>>>>>>
> > >      >>>>>>>>
> > >     https://gist.github.com/gem-pete/d8d7ab220dc8781f0827f965f09d43ed
> > >     <https://gist.github.com/gem-pete/d8d7ab220dc8781f0827f965f09d43ed
> >
> > >      >>>>>>> That doesn't look right at all.  Are you sure the kernel
> > >     matches the
> > >      >>>>>>> vmcore?  Also, which kgdb version are you using?
> > >      >>>>>>>
> > >      >>>>>> yea i agree that doesn't look right at all.  here is my
> setup:
> > >      >>>>>>
> > >      >>>>>> $ which kgdb
> > >      >>>>>> /usr/bin/kgdb
> > >      >>>>>> $ kgdb
> > >      >>>>>> GNU gdb 6.1.1 [FreeBSD]
> > >      >>>>>> $ ls -lh /var/crash/vmcore.1
> > >      >>>>>> -rw-------  1 root  wheel   1.6G Jul  3 15:03
> > >     /var/crash/vmcore.1
> > >      >>>>>> $ ls -l /usr/lib/debug/boot/kernel/kernel.debug
> > >      >>>>>> -r-xr-xr-x  1 root  wheel  87840496 Jul  3 13:54
> > >      >>>>>> /usr/lib/debug/boot/kernel/kernel.debug
> > >      >>>>>>
> > >      >>>>>> and i invoke kgdb like so:
> > >      >>>>>> $ sudo kgdb /usr/lib/debug/boot/kernel/kernel.debug
> > >     /var/crash/vmcore.1
> > >      >>>>>>
> > >      >>>>>> here's a gist of my full gdb session:
> > >      >>>>>> http://termbin.com/krsn
> > >      >>>>>>
> > >      >>>>>> dunno - maybe i have a bad core dump?  regardless, more
> than
> > >     happy to
> > >      >>>>>> help so let me know if i should try anything else or
> patches
> > >     etc..
> > >      >>>>> Can you try installing gdb from ports and using
> > >     /usr/local/bin/kgdb?
> > >      >>>>>
> > >      >>>>
> > >      >>>> that seems to have done the trick, at least the output looks
> more
> > >      >>>> encouraging.
> > >      >>>>
> > >      >>>>   --- trap 0, rip = 0, rsp = 0, rbp = 0 ---
> > >      >>>> KDB: enter: panic
> > >      >>>>
> > >      >>>> __curthread () at ./machine/pcpu.h:231
> > >      >>>> 231        __asm("movq %%gs:%1,%0" : "=r" (td)
> > >      >>>>
> > >      >>>>
> > >      >>>> here's my full kgdb session:
> > >      >>>> http://termbin.com/qa4f
> > >      >>>>
> > >      >>>> i don't see any threads not in "sched_switch" though :(
> > >      >>>
> > >      >>> Hi,
> > >      >>>
> > >      >>> The problem may be that the patch to enable atomic inlining
> of all
> > >      >>> macros forgot to set the SMP keyword which means SMP is not
> > >     defined at
> > >      >>> all for KLD's so all non-kernel atomic usage is with MPLOCKED
> > >     empty!
> > >      > Problem is that out-of-tree modules build does not have opt*.h
> files
> > >      > from the kernel.  UP config is a valid one, flipping some
> option's
> > >      > default value does not solve the problem.
> > >
> > >     Yes, but using the lock prefix in a generic module is ok (it will
> still
> > >     work, just not quite as fast) whereas the lack of lock is fatal on
> > >     SMP.  I would amend Hans' patch slightly to honor the opt_* setting
> > >     for KLD_TIED (but that is only true if KLD_TIED means "built as
> part of
> > >     a kernel build, so has valid opt_foo.h headers" and not
> > >     'a standalone module where someone put MODULES_TIED=1 on the
> command
> > >     line
> > >     to make').
> > >
> > >
> > > I agree with this default. It's sensible to default to (a) the most
> > > popular thing and (b) thing that always works, especially when (a) and
> > > (b) are identical.
> > >
> > > Don't make me start the "Do we really need an SMP option, why not make
> > > it always on" thread :) The number of relevant uniprocessor x86 boxes
> > > that benefit from omitting SMP is so small as to be irrelevant, IMHO.
> A
> > > MP kernel runs just fine on them...
> > >
> > > Warner
> >
> > Where are we on this?
> > It is important to get it fixed, it's already been 4 days, which means 4
> > days of all modern FreeBSD desktop systems being broken, and possibly
> > other systems with kernel modules from ports as well.
> >
> >
> > Another question, how hard would it be to expose how the kernel was
> > built to modules built from ports, so that they can figure out stuff
> > like SMP and others, that might affect the module build?
> Point the KERNBUILDDIR variable to the directory of the kernel build.
> This is the directory where *.o and opt*.h are located.  Then everything
> would just work.
>

Is the solution that we require everyone to build a kernel before they can
build the standalone modules or am I missing something here?

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Received on Fri Jul 06 2018 - 07:14:41 UTC

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