[Qemu-devel] [Bug 1319100] Re: qemu-arm-static bug in signal handling avoids using mono

[Serge Hallyn <1319100@bugs.launchpad.net>]

** Changed in: qemu-kvm (Ubuntu)
       Status: New => Confirmed

** Changed in: qemu-kvm (Ubuntu)
   Importance: Undecided => Wishlist

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https://bugs.launchpad.net/bugs/1319100

Title:
  qemu-arm-static bug in signal handling avoids using mono

Status in QEMU:
  New
Status in qemu-kvm package in Ubuntu:
  Confirmed
Status in qemu-kvm package in Debian:
  Confirmed

Bug description:
  Note, this bug is already reported to debian, but it seems to also affect the upstream code.
  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=748043

  running mono in a chroot environment with qemu-user-static is not posible
  because at least one signal used during termination of mono is routed to the
  host.

  This can be reproduced by:
  debootstrap --include=mono-runtime --foreign --arch=armel "wheezy" "mono-test" "http://ftp.de.debian.org//debian"
  cp /usr/bin/qemu-arm-static mono-test/usr/bin
  mount -t proc none mono-test/proc
  mount -o bind /dev mono-test/dev
  mount -o bind /sys mono-test/sys
  chroot mono-test
  ../debootstrap/debootstrap --second-stage
  exit
  mount -t proc none mono-test/proc
  mount -o bind /sys mono-test/sys
  chroot mono-test
  QEMU_STRACE=1 /usr/bin/mono /usr/lib/mono/4.0/gacutil.exe

  This will block on a futex:

  --8<--
  18663 sched_yield(0,0,2582980,0,0,2582928) = 0
  18663 clock_gettime(1,-150996384,2,1,2585016,2585600) = 0
  18663 tgkill(18663,18664,30,18664,30,-161951744) = 0
  18663 futex(0x00293774,FUTEX_PRIVATE_FLAG|FUTEX_WAIT,0,NULL,NULL,0)
  --8<--

  If you use mono within strace on a native x86 box you can see, that signals
  between threads are used during termination:

  strace -f -o log.txt /usr/bin/mono /usr/lib/mono/4.0/gacutil.exe

  --8<--
  14075 sched_yield()                     = 0                                     
  14075 tgkill(14075, 14083, SIGPWR)      = 0                                     
  14075 futex(0x983f00, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>              
  14083 <... futex resumed> )             = ? ERESTARTSYS (To be restarted)       
  14083 --- SIGPWR (Power failure) @ 0 (0) ---                                    
  14083 futex(0x983f00, FUTEX_WAKE_PRIVATE, 1) = 1                                
  14075 <... futex resumed> )             = 0                                     
  14083 rt_sigsuspend(~[INT QUIT ABRT TERM XCPU RTMIN RT_1] <unfinished ...>      
  14075 futex(0x94d9a4, FUTEX_CMP_REQUEUE_PRIVATE, 1, 2147483647, 0x94da20, 24) = 3
  14078 <... futex resumed> )             = 0                                     
  14078 futex(0x94da20, FUTEX_WAKE_PRIVATE, 1) = 1                                
  14077 <... futex resumed> )             = 0                                     
  14075 futex(0x94d9a4, FUTEX_CMP_REQUEUE_PRIVATE, 1, 2147483647, 0x94da20, 26 <unfinished ...>
  --8<--

  This also blocks the installation of libnunit2.6-cil within a armel chroot,
  because it uses mono in its postinst script.
  E.g. (/usr/bin/mono /usr/share/mono/MonoGetAssemblyName.exe /usr/lib/cli/nunit.core-2.6/nunit.core.dll)

  Obviously the same as described in:
  http://lists.opensuse.org/opensuse-arm/2011-12/msg00000.html
  is happening here.

  There is an openSuSE patch against qemu:
  https://build.opensuse.org/package/view_file/Virtualization:Qemu/qemu/0002-XXX-work-around-SA_RESTART-race-wit.patch?expand=1

  This patch also applies against qemu from backports-wheezy and resolves this
  issue.

  As it seems, that this issue is not Debian specific i will also report it to
  the qemu project and reference this bug report.

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