Re: RCU question

[George Anzinger]

Manfred Spraul wrote:
> Zwane Mwaikambo wrote:
>
> > On Fri, 10 Dec 2004, George Anzinger wrote:
> >
> >  
> >
> > > That is ok.  Either we have interrupts off and no softirqs are 
> > > pending and we
> > > proceed to the "hlt" (where the interrupt will be taken), or softirqs 
> > > are
> > > pending, we turn interrupts on, do the softirq, turn interrupts off 
> > > and try
> > > again.  Unless some tasklet (RCU?) never "gives up" or we will exit 
> > > the while
> > > with interrupts off and move on to the "hlt".  Or did I miss something?
> > >   
> >
> >
> > But the point is that you cannot execute hlt with interrupts disabled.
> >  
> The trick is the sti instruction: It enables interrupt processing after 
> the following instruction.
>
> Thus
>    sti
>    hlt
>
> cannot race - it atomically enables interrupts and waits.

Exactly :)

--
George Anzinger   george@xxxxxxxxxx
High-res-timers:  http://sourceforge.net/projects/high-res-timers/

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