Bug 1687171

Well, skipping the test is one option, but as the author of the faulthandler module, I would prefer to see the test passing :-)

Can you please try copy/paste the following code in a script file and run "python3 script.py"?

Script:
---
import faulthandler, signal, os

def handler(signum, frame):
    handler.called = True
handler.called = False

faulthandler.enable()

signum = signal.SIGUSR1
signal.signal(signum, handler)
faulthandler.register(signum, chain=True)
os.kill(os.getpid(), signum)
print("called", handler.called)
---

Expected output:
---
Current thread 0x00007fc3ad534600 (most recent call first):
  File "script.py", line 12 in <module>
called True
---

If you get a segfault, there is a bug somewhere.

Maybe try also the script with Python 3.6 ou 3.7 on the same CPU.

test_faulthandler is tested upstream on a wide range of architectures. I'm not aware of any failure, at least on Python 3.7 and 3.8 (dev version).

$ python3.4 script.py 
Current thread 0x00007ff7e72e5740 (most recent call first):
  File "script.py", line 12 in <module>
called True
Fatal Python error: Segmentation fault

Current thread 0x00007ff7e72e5740 (most recent call first):
Segmentation fault

$ python3.6 script.py 
Current thread 0x00007f5c1b0a6740 (most recent call first):
  File "script.py", line 12 in <module>
called True
Fatal Python error: Segmentation fault

Current thread 0x00007f5c1b0a6740 (most recent call first):
Segmentation fault

On the other hand, if run on kvm host, it works - so this might be issue with kvm guest?

$ python3.6 script.py 
Current thread 0x00007f9107e55740 (most recent call first):
  File "script.py", line 12 in <module>
called True

  <cpu mode='custom' match='exact' check='full'>
    <model fallback='forbid'>Skylake-Server-IBRS</model>
    <vendor>Intel</vendor>
    <feature policy='disable' name='ds'/>
    <feature policy='disable' name='acpi'/>
    <feature policy='require' name='ss'/>
    <feature policy='disable' name='ht'/>
    <feature policy='disable' name='tm'/>
    <feature policy='disable' name='pbe'/>
    <feature policy='disable' name='dtes64'/>
    <feature policy='disable' name='monitor'/>
    <feature policy='disable' name='ds_cpl'/>
    <feature policy='disable' name='vmx'/>
    <feature policy='disable' name='smx'/>
    <feature policy='disable' name='est'/>
    <feature policy='disable' name='tm2'/>
    <feature policy='disable' name='xtpr'/>
    <feature policy='disable' name='pdcm'/>
    <feature policy='disable' name='dca'/>
    <feature policy='disable' name='osxsave'/>
    <feature policy='disable' name='tsc_adjust'/>
    <feature policy='require' name='clflushopt'/>
    <feature policy='require' name='pku'/>
    <feature policy='disable' name='ospke'/>
    <feature policy='require' name='stibp'/>
    <feature policy='require' name='ssbd'/>
    <feature policy='require' name='hypervisor'/>
    <feature policy='disable' name='arat'/>
  </cpu>

CPU config on vm, that is copy from host.

Changing CPU typo of vm to Skylake-Client-IBRS works around the issue - so I guess this is bug in virtualization.

It's still unclear to me if it's a bug in Python or in the virtualization :-(

This bug has been fixed in Python 3.7, 3.8 and future 3.9: https://bugs.python.org/issue21131

Unfortunately, backporting this is not going far enough on my priority list. To rebuild in Mock, please apply the patch locally.