Re: atomic changes break drm-next-kmod?

From: Konstantin Belousov <kostikbel_at_gmail.com>
Date: Fri, 6 Jul 2018 11:47:30 +0300
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.
Received on Fri Jul 06 2018 - 06:47:42 UTC

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