Re: [PATCH v6 4/4] hw: replace most qemu_bh_new calls with qemu_bh_new_guarded

[Alexander Bulekov <alxndr@bu.edu>]

[[ CCing qemu-devel in case someone can spot something wrong faster than me]]

On 230308 1042, Thomas Huth wrote:

[snip]

> > > I'd really love to see this series included in QEMU 8.0, so to help with
> > > testing a little bit, I've put it in my gitlab-CI for testing. However, it
> > > hit a segfault in the macOS runner:
> > > 
> > > https://gitlab.com/thuth/qemu/-/jobs/3889796931#L4757
> > > 
> > > Do you have an idea what might be going wrong here?
> > > 
> > 
> > Unfortunately I wasn't able to reproduce this on x86_64 linux and I
> > don't have a mac to test on. I will try to comb through the code in
> > patch 4/4 as that seams like the most likely culprit.
> 
> Yes, you're right, it's the final patch that is causing the problem. I've
> pushed the branch without the final patch, and here it was still working
> fine:
> 
>  https://gitlab.com/thuth/qemu/-/jobs/3893883020
> 
> I also don't have a mac for testing, but cirrus-ci recently started to offer
> terminal access to the jobs ... so if you've got a github account, you could
> fork the qemu repo there and enable the cirrus-ci for it in the marketplace.
> See .gitlab-ci.d/cirrus/README.rst for how to trigger it via the gitlab-CI.
> Or if that's too complicated right now, let me know if I can test something
> for you in my setup.

The detailed cirrus logs indicate that the last test in bios-tables-test
was /x86_64/acpi/q35/multif-bridge and it started qemu with these devices:

-display none -machine q35 -accel kvm -accel tcg -net none -S -device
virtio-balloon,id=balloon0,addr=0x4.0x2 -device
pcie-root-port,id=rp0,multifunction=on,port=0x0,chassis =1,addr=0x2
-device pcie-root-port,id=rp1,port=0x1,chassis=2,addr=0x3.0x1 -device
pcie-root-port,id=rp2,port=0x0,chassis=3,bus=rp1,addr=0.0 -device
pci-bridge,bus=rp2,chassis_nr=4,id=br1 -device
pcie-root-port,id=rphptgt1, port=0x0,chassis=5,addr=2.1 -device
pcie-root-port,id=rphptgt2,port=0x0,chassis=6,addr=2.2 -device
pcie-root-port,id=rphptgt3,port=0x0,chassis=7,addr=2.3 -device
pci-testdev,bus=pcie.0,addr=2.4 -device pci-testdev,bus=pcie .0,addr=5.0
-device pci-testdev,bus=rp0,addr=0.0 -device pci-testdev,bus=br1 -drive
id=hd0,if=none,file=tests/acpi-test-disk-0q5LlN,format=raw -device
ide-hd,drive=hd0

using these identical arguments I still could not reproduce the issue
(replacing the test disk). The test attaches a few devices but it
doesn't seem like they would be related. 

Out of the listed devices, the ones that were touched in patch 4 seem to
be virtio-balloon and ide. 

I took at quick look at the corresponding changes and didn't immediately
notice something wrong, but I'll keep digging. Still have no clue why it
would only show up on mac (I tried different compilers and asan).

-Alex