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DateSat, 11 Dec 2004 08:52:02 -0800
FromGeorge Anzinger <>
SubjectRe: RCU question
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@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/

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