[Qemu-devel] [Bug 1098729] Re: qemu-user-static for armhf: segfault in threaded code

[Erik de Castro Lopo]

At the top of function  cpu_unlink_tb() in translate-all.c:

  /* FIXME: TB unchaining isn't SMP safe.  For now just ignore the
       problem and hope the cpu will stop of its own accord.  For userspace
       emulation this often isn't actually as bad as it sounds.  Often
       signals are used primarily to interrupt blocking syscalls.  */

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https://bugs.launchpad.net/bugs/1098729

Title:
  qemu-user-static for armhf: segfault in threaded code

Status in QEMU:
  New

Bug description:
  
  Currently running QEMU from git (fedf2de31023) and running the armhf version 
of qemu-user-static which I have renamed qemu-armhf-static to follow the naming 
convention used in Debian.

  The host systems is a Debian testing x86_64-linux and I have an Debian
  testing armhf chroot which I invoke using schroot.

  Majority of program in the armhf chroot run fine, but I'm getting qemu
  segfaults in multi-threaded programs.

  As an example, I've grabbed the threads demo program here:

  https://computing.llnl.gov/tutorials/pthreads/samples/dotprod_mutex.c

  and changed NUMTHRDS from 4 to 10. I compile it as (same compile
  command on both x86_64 host and armhf guest):

      gcc -Wall -lpthread dotprod_mutex.c -o dotprod_mutex

  When compiled for x86_64 host it runs perfectly and even under
  Valgrind displays no errors whatsoever.

  However, when I compile the program in my armhs chroot and run it it
  usually (but not always) segaults or hangs or crashes. Example output:

  
      (armhf) $ ./dotprod_mutex
      Thread 1 did 100000 to 200000:  mysum=100000.000000 global 
sum=100000.000000
      Thread 0 did 0 to 100000:  mysum=100000.000000 global sum=200000.000000
      TCG temporary leak before f6731ca0
      qemu-arm-static: 
/home/erikd/Git/qemu-posix-timer-hacking/Upstream/tcg/tcg-op.h:2371:
      tcg_gen_goto_tb: Assertion `(tcg_ctx.goto_tb_issue_mask & (1 << idx)) == 
0' failed.

  
      (armhf) $ ./dotprod_mutex
      qemu: uncaught target signal 11 (Segmentation fault) - core dumped
      Segmentation fault

      (armhf) $ ./dotprod_mutex
      qemu-arm-static: 
/home/erikd/Git/qemu-posix-timer-hacking/Upstream/tcg/tcg.c:519:
      tcg_temp_free_internal: Assertion `idx >= s->nb_globals && idx < 
s->nb_temps' failed.

  
      (armhf) $ ./dotprod_mutex
      Thread 1 did 100000 to 200000:  mysum=100000.000000 global 
sum=100000.000000
      qemu: uncaught target signal 11 (Segmentation fault) - core dumped
      Segmentation fault

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