Re: Problem with LIST_HEAD and list_add (was Page Fault Handler Hijacking and Oops)

[Jim Cromie <jcromie@xxxxxxxxxx>]

Jan Hudec wrote:

> On Fri, Aug 05, 2005 at 20:18:44 +0000, Vincenzo Mallozzi wrote:
>  
>
> > In oder word, I've read in various Linux Kernel book (like Linux Kernel 
> > Programming, Linux Kernel Development, etc) that the use of spin lock in 
> > Interrupt Handler function must be very limited. Is it true?
> >    
>
> Um, yes. And use of spin-lock should ALWAYS be very limited.
>
>  
can you be more quantitative here ?

whats the average duration of a blocking spinlock in the various 
PREMPT_* flavors ?
whats a good target 'minimum' locked time for an un-contended lock ?
what is the overhead (in whatever units) for each kind of lock

are these factors in the choice, or are they completely overwhelmed by 
structural factors ?
like: thou shalt not sleep with this kind of lock taken,

these are probably poorly formulated questions,
but hopefully the idea/desire is clear enough

tia

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