[En-Nut-Discussion] Not fixed!!!: Re: confirmed!!! Re: NutOS 4.4.0 on ARM7: possibly bug in NutEnterCritical / NutExitCritical

[Ole Reinhardt]

Hi,

> > NutEnterCriticalWithFlags(&flags)
> > NutExitCriticalWithFlags(flags)
> 
> Is this a typo that the second line does not have "(&flags)"??

Not necessary a typo. Have to think about it...

> May I suggest that more than one option be available? Due to ARM's 
> pipeline structure, a local memory takes too many cicles to write/read, 
> so there could be:
> 
> 1) a stack version, could be the old one and to be used with care,
> 2) a register version. Question: how to make sure it goes to a resister? 
> This would be the fastest version, good for ISR.
> 3) a memory variable version, 100% safe, and leave it to the compiler to 
> optimize to register if possible at all. It could even allocate it's own 
> temorary variable.
> 
> (1) and (2) would come with big warnings, leaving only (3) for most 
> novice programers...

Good idea. I could think about a fourth version where we only disable a
special interrupt if the critical section is not vulnerable to other
interrupts. AFAIK linux also implements differen kind of spinlocks.

Bye,

Ole
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