> On Nov 6, 2019, at 3:58 PM, Dario Faggioli <dfaggi...@suse.com> wrote:
>
> In a dom0less configuration, if the null scheduler is used, the system
> may fail to boot, because the loop in null_unit_wake() never exits.
>
> Bisection showed that this behavior occurs since commit d545f1d6 ("xen:
> sched: deal with vCPUs being or becoming online or offline") but the
> real problem is that, in this case, pick_res() always return the same
> CPU.
>
> Fix this by only deal with the simple case, i.e., the vCPU that is
> coming online can be assigned to a sched. resource right away, in
> null_unit_wake().
>
> If it can't, just add it to the waitqueue, and we will deal with it in
> null_schedule(), being careful about not racing with vcpu_wake().
>
> Reported-by: Stefano Stabellini <sstabell...@kernel.org>
> Signed-off-by: Dario Faggioli <dfaggi...@suse.com>
> Tested-by: Stefano Stabellini <sstabell...@kernel.org>
Reviewed-by: George Dunlap <george.dun...@citrix.com>
With one minor nit…
> + * and it's previous resource is free (and affinities match), we can just
its (no ‘). I’ll change this on check-in.
-George
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