Re: panic: vm_page_free_toq: freeing mapped page

On Mon, 13.07.2009 at 13:29:56 -0500, Alan Cox wrote:
> Ulrich Spörlein wrote:
> > On Mon, 13.07.2009 at 19:15:03 +0200, Ulrich Spörlein wrote:
> >   
> >> On Sun, 12.07.2009 at 14:22:23 -0700, Kip Macy wrote:
> >>     
> >>> On Sun, Jul 12, 2009 at 1:31 PM, Ulrich Spörlein<uqs_at_spoerlein.net> wrote:
> >>>       
> >>>> Hi,
> >>>>
> >>>> 8.0 BETA1 _at_ r195622 will panic reliably when running the clang static
> >>>> analyzer on a buildworld with something like the following panic:
> >>>>
> >>>> panic: vm_page_free_toq: freeing mapped page 0xffffff00c9715b30
> >>>> cpuid = 1
> >>>> KDB: stack backtrace:
> >>>> db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
> >>>> panic() at panic+0x182
> >>>> vm_page_free_toq() at vm_page_free_toq+0x1f6
> >>>> vm_object_terminate() at vm_object_terminate+0xb7
> >>>> vm_object_deallocate() at vm_object_deallocate+0x17a
> >>>> _vm_map_unlock() at _vm_map_unlock+0x70
> >>>> vm_map_remove() at vm_map_remove+0x6f
> >>>> vmspace_free() at vmspace_free+0x56
> >>>> vmspace_exec() at vmspace_exec+0x56
> >>>> exec_new_vmspace() at exec_new_vmspace+0x133
> >>>> exec_elf32_imgact() at exec_elf32_imgact+0x2ee
> >>>> kern_execve() at kern_execve+0x3b2
> >>>> execve() at execve+0x3d
> >>>> syscall() at syscall+0x1af
> >>>> Xfast_syscall() at Xfast_syscall+0xe1
> >>>> --- syscall (59, FreeBSD ELF64, execve), rip = 0x800c20d0c, rsp = 0x7fffffffd6f8, rbp = 0x7fffffffdbf0 ---
> >>>>         
> >>> Can you try the following change:
> >>>
> >>> http://svn.freebsd.org/viewvc/base/user/kmacy/releng_7_2_fcs/sys/vm/vm_object.c?r1=192842&r2=195297
> >>>       
> >> Applied this to HEAD by hand an ran with it, it died 20-30 minutes into
> >> the scan-build run. So no luck there. Next up is a test using the
> >> GENERIC kernel.
> >
> > No improvement with a GENERIC kernel. Next up will be to run this with
> > clean sysctl, loader.conf, etc. Then I'll try disabling SMP.
> >
> > Does the backtrace above point to any specific subsystem? I'm using UFS,
> > ZFS and GELI on this machine and could try a few combinations...
> 
> The interesting thing about the backtrace is that it shows a 32-bit i386 
> executable being started on a 64-bit amd64 machine.  I've seen this 
> backtrace once before, and you'll find it in the PR database.  In that 
> case, the problem "went away" after the known-to-be-broken 
> ZERO_COPY_SOCKETS option was removed from the reporter's kernel 
> configuration.  However, I don't see that as the culprit here.

Hi Alan, first the bad news

I ran this test with a GENERIC kernel, SMP disabled, hw.physmem set to 2
GB in single user mode, so no other processes or deamons running,
nothing special in loader.conf except for ZFS and GELI. It reliably
panics, so nothing new here.

Now the good news, you may be able to crash your own amd64 box in 3
minutes by doing:

mkdir /tmp/foo && cd /tmp/foo
fetch -o- https://www.spoerlein.net/pub/llvm-clang.tar.gz | tar xf -
while :; do for d in bin sbin usr.bin usr.sbin; do $PWD/scan-build -o /dev/null -k make -C /usr/src/$d clean obj depend all; done; done

Please note that scan-build/ccc-analyzer wont actually do anything, as
they cannot create output in /dev/null. So this is just running the
perl-script and forking make/sh/awk/ccc-analyzer like mad. It does not
survive 3 minutes on my Core2 Duo 3.3 GHz.

hth
Ulrich Spörlein