Re: [Qemu-devel] [s390] possible deadlock in handle_sigp?

[Paolo Bonzini]

On 12/09/2016 19:37, Christian Borntraeger wrote:
> On 09/12/2016 06:44 PM, Paolo Bonzini wrote:
> > I think that two CPUs doing reciprocal SIGPs could in principle end up
> > waiting on each other to complete their run_on_cpu.  If the SIGP has to
> > be synchronous the fix is not trivial (you'd have to put the CPU in a
> > state similar to cpu->halted = 1), otherwise it's enough to replace
> > run_on_cpu with async_run_on_cpu.
> 
> IIRC the sigps are supossed to be serialized by the big QEMU lock. WIll 
> have a look.

Yes, but run_on_cpu drops it when it waits on the qemu_work_cond
condition variable.  (Related: I stumbled upon it because I wanted to
remove the BQL from run_on_cpu work items).

Paolo