[Bug 1776478] Re: Getting qemu: uncaught target signal 6 when running lv2 plugin cross-compilation

[Paul Guyot]

Hello,

I believe I experienced the same bug in a similar context: using QEMU
Linux user emulation for continuous integration on GitHub Actions. As a
workaround, I did run the chroot script with taskset -c 0 to limit
execution on a single CPU which has been solving the problem for more
than 10 successive runs. @guysoft does taskset fixes your problem?

This was with qemu 4.2 as packaged by Ubuntu. The environment (automated
CI) makes it difficult to plug gdb.

In my case, the crash happens with PostgreSQL.
https://www.postgresql.org/message-id/86C24765-95F7-464F-9677-B09A396A5F69%40kallisys.net

It may be related to the way QEMU acquires a global lock to ensure
memory barrier semantic on ARM or to the way QEMU interprets RaspberryPi
Zero (armv6l) memory barrier cp15 instruction which is different from
newer cores. I have yet to find where this is implemented in qemu source
code to investigate. @pmaydell could you please provide any pointer?

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https://bugs.launchpad.net/bugs/1776478

Title:
  Getting qemu: uncaught target signal 6 when running  lv2 plugin cross-
  compilation

Status in QEMU:
  Incomplete

Bug description:
  Hey,
  I am part of the Zynthian team and we use qemu-arm-static to cross compile 
lv2 audio plugins.

  When running a compilation of DISTRHO-Ports we get:

  lv2_ttl_generator: pthread_mutex_lock.c:81: __pthread_mutex_lock: Assertion 
`mutex->__data.__owner == 0' failed.
  qemu: uncaught target signal 6 (Aborted) - core dumped
  ./scripts/generate-ttl.sh: line 27: 16524 Aborted                 $GEN ./$FILE
  Makefile:62: recipe for target 'gen_lv2' failed
  make[1]: *** [gen_lv2] Error 134
  make[1]: Leaving directory '/home/pi/zynthian-sw/plugins/DISTRHO-Ports'
  Makefile:104: recipe for target 'lv2' failed
  make: *** [lv2] Error 2

  
  lv2_ttl_generator source is here:
  https://github.com/DISTRHO/DISTRHO-Ports/tree/master/libs/lv2-ttl-generator

  The command that is ruining is
  lv2_ttl_generator ./TAL-Filter-2.so 

  And ./TAL-Filter-2.so source is here:
  https://github.com/DISTRHO/DISTRHO-Ports/tree/master/ports/tal-filter-2/source


  Is there a way to debug what is going on?
  This runs fine on a Raspberrypi which is armv7

  A workaround would also help.

  
  Bug in Zynthian:
  https://github.com/zynthian/zynthian-sys/issues/59
  Bug in DISTRHO-Ports:
  https://github.com/DISTRHO/DISTRHO-Ports/issues/29

  Using qemu-arm-static version from master from two days ago:
  qemu-arm version 2.12.50 (v2.12.0-1182-ga7a7309ca5-dirty), commit: 
a7a7309ca52c327c6603d60db90ae4feeae719f7

  Also saw this in qemu-arm version 2.12.0 (Debian 1:2.12+dfsg-3)

  Thanks,
  Guy

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