DragonFly site

Erik Wikström erik-wikstrom at telia.com
Sat Apr 1 02:14:38 PST 2006

On 2006-04-01 05:50, Trevor Kendall wrote:

On the site I have noticed a number of issues. Most are easily fixed,
but I'm not sure about this one.
On http://www.dragonflybsd.org/docs/goals.cgi
Serializing tokens may also be used to protect threads from preempting
interrupts that attempt to obtain the same token. This is a slightly
different effect from the Big Giant Lock (also known as the MP lock),
which does not interlock against interrupts on the same cpu. It is
important to note that token atomicity is maintained through
preemptive conditions, even though preemption involves a temporary
switch to another thread. It is not necessary to enter a spl() level
or critical section to preserve token atomicity.
Weren't the spl set of functions removed?
Yes, since they are no longer necessary, just as it says. As I 
understand things the above text explains the difference between using 
serializing tokens and BGL when dealing with preemption, and says that 
with tokens there is not need for spl().

Erik Wikström
 "I have always wished for my computer to be as easy to use as my
 telephone; my wish has come true because I can no longer figure
 out how to use my telephone" -- Bjarne Stroustrup

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