Re: [PATCH] accel: Fix qtest deadlock during unplug

[Fabiano Rosas <farosas@suse.de>]

Shivang Upadhyay <shivangu@linux.ibm.com> writes:

> On Wed, 2026-09-23 at 10:05 -0300, Fabiano Rosas wrote:
>> 
>> @Shivang, we're discussing about cpu_remove_sync() down in this
>> thread,
>> maybe that's of interest to you. Philippe is suggesting we could
>> maybe
>> move the call up a layer.
>
> Hi Fabiano, 
>  I checked the dummp_cpu way to working, I can see you changes makes
> sense here. I couldn't understand much from Philippe's suggestion. Do
> we want to handle the case for thread waiting on sigwait, inside
> cpu_remove_sync ?
>

The point was simply to call cpu_remove_sync() from another spot. I
think he made the same suggestion to you here:
https://lore.kernel.org/r/bb91d62a-f15a-42e5-813d-5ec7e6d92479@oss.qualcomm.com

While researching what would it take to do it, I got concerned about the
effects that setting cpu->unplug could have for targets that currently
do not set it, but nonetheless use it as the cpu loop exit
condition. That question is still open, I haven't got time to look
deeper into it yet.

If you're interested in that area, you could give it a try. As I
mentioned in the other email, the unplug logic was added back then to
improve the usability of spapr cpu hot-unplug so it could be pertinent
to anyone working on ppc.