Re: [Xen-devel] [PATCH] xen: make sure stop_machine_run() is always called in a tasklet

[Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>]

On 11/02/2020 09:35, Juergen Gross wrote:
> With core scheduling active it is mandatory for stop_machine_run() to
> be called in a tasklet only, as otherwise a scheduling deadlock would
> occur: stop_machine_run() does a cpu rendezvous by activating a tasklet
> on all other cpus. In case stop_machine_run() was not called in an idle
> vcpu it would block scheduling the idle vcpu on its siblings with core
> scheduling being active, resulting in a hang.

I suppose rcu_barrier() is fine due to process_pending_softirqs() being
called inside? I'm a little concerned by imposing is_vcpu_idle() restriction
in that case as rcu_barrier() could be technically called from a non-tasklet
context.

Igor

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