Messages in this thread | | | Date | Tue, 14 Sep 2010 09:37:56 -0400 | From | Don Zickus <> | Subject | Re: [RFC 4/6] x86, NMI, Rewrite NMI handler |
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On Tue, Sep 14, 2010 at 01:12:41PM +0800, Huang Ying wrote: > On Mon, 2010-09-13 at 22:04 +0800, Don Zickus wrote: > > On Mon, Sep 13, 2010 at 10:09:30AM +0800, Huang Ying wrote: > > > > The reason I asked was, I thought it would be easier to have a global > > > > variable that tells the nmi handler which cpu has the NMI's routed to its > > > > io port. This way if you want to swap out the bsp cpu, you could perhaps > > > > just re-route the nmi to a new cpu and the global variable would be > > > > updated accordingly? > > > > > > Then we need some kind of protection or race condition between > > > re-routing NMI and updating the variable. Do you think so? > > > > Well, I thought the only reasonable place to update the variable is when > > the cpu is being taken offline, during the MTRR update. Since no NMIs can > > be processed when the cpu's are syncing their MTRR, there shouldn't be a > > race condition, no? > > > > Then again I am probably missing something obvious. Like I don't know how > > cpu's deal with interrupts/NMIs when they are going offline. > > > > It was just a thought to avoid the spinlock. > > Why do you hate spinlock inside NMI handler? I think it is safe and > simple if only used in NMI handler.
I guess I always had the mentality that spinlocks in an NMI context was a big no-no. Never really thought about if there were safe use-cases or not.
Cheers, Don
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