Subject: Re: [PATCH][RFC] preempt_count corruption across H_CEDE call with CONFIG_PREEMPT on pseries

From: Benjamin Herrenschmidt <[email-masked]>
Date: Fri, 23 Jul 2010 15:11:00 +1000

On Fri, 2010-07-23 at 10:38 +0530, Vaidyanathan Srinivasan wrote:
> Yes.  extended_cede_processor() will return with interrupts enabled in
> the cpu. (This is done by the hypervisor).  Under normal cases we
> cannot be interrupted because no IO interrupts are routed to us after
> xics_teardown_cpu() and since the CPU is out of the map, nobody will
> send us IPIs.

What about decrementer ?

> Though H_CEDE will return with interrupts enabled, it is unlikely that
> an interrupt can be delivered in this context. 

Well, if interrupts are soft-disabled, even if one occurs, we will just
mask and return, so that at least should be ok.

Cheers,
Ben.