Re: [PATCH 3/3] plugins: avoid failing plugin when CPU is inited several times

[Alex Bennée]

Emilio G. Cota <address@hidden> writes:

> On Mon, May 11, 2020 at 18:53:19 +0300, Nikolay Igotti wrote:
>> Attached to the mail counter.c when running with attached test.c compiled
>> to Linux standalone binary shows failing assert, unless the patch is
>> applied.
>
> I didn't get the attachment. Can you paste the code at the end of your
> reply?

So the problem is we are recycling cpu_index:

  21:01:54 [alex@zen:~/l/q/b/all.plugin] plugins/next|●2✚3…(+8 insertions(+)) 
127 + ./x86_64-linux-user/qemu-x86_64 ./tests/tcg/x86_64-linux-user/threadcount
  cpu_list_add: 0x5605598579f0
  cpu_get_free_index: 0
  cpu_list_add: 0x5605598c6010
  cpu_get_free_index: 1
  cpu_list_add: 0x5605598ec330
  cpu_get_free_index: 2
  cpu_list_add: 0x560559912a30
  cpu_get_free_index: 3
  cpu_list_add: 0x560559939130
  cpu_get_free_index: 4
  cpu_list_add: 0x56055995d360
  cpu_get_free_index: 1
  **
  ERROR:/home/alex/lsrc/qemu.git/plugins/core.c:205:qemu_plugin_vcpu_init_hook: 
assertion failed: (success)
  qemu:handle_cpu_signal received signal outside vCPU context @ 
pc=0x7fa29c702613

However I'm confused as to how. The cpu_index is really just a function
of the number of CPUs in the cpus list and I can't see where we free
them up. We never call cpu_common_unrealizefn so the list should never
shrink. We should just end up with a slowly growing list of now dead CPU
states.

I'm giving up for now but will have a look again in the morning if no
one else has figured out what is going on by then.

>
> Thanks,
>               Emilio


-- 
Alex Bennée