Re: [Xen-devel] [PATCH 2/2] xen: sched: we never get into context_switch() with prev==next

[George Dunlap <George.Dunlap@xxxxxxxxxx>]

> On Apr 20, 2019, at 4:24 PM, Dario Faggioli <dfaggioli@xxxxxxxx> wrote:
> 
> In schedule(), if we pick, as the next vcpu to run (next) the same one
> that is running already (prev), we never get to call context_switch().
> 
> We can, therefore, get rid of all the `if`-s testing prev and next being
> different, trading them with an ASSERT() (on ARM, the ASSERT() was even
> already there!)

Keeping in mind that ASSERT() is merely a debugging aid: suppose that testing 
didn’t discover this, and a bug that violated this assumption slipped into 
production.  Would the patched code DTRT?

It sort of looks like the prev/next checking is an optimization, and that 
duplicate checking shouldn’t cause any problems.  Is that the case?

 -George

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