Re: "objtrm" problem probably found (was Re: Stuck in "objtrm")

[John-Mark Gurney]

Matthew Dillon scribbled this message on Jul 12:
>     p.s.  I'm pretty sure that the lock prefix costs nothing on a UP system,
>     and probably wouldn't be noticed on an SMP system either because the
>     write-allocation overhead is already pretty bad.  But I haven't tested
>     it.

actually, I'm not so sure, it guarantees that NO other bus operation
will succeed while this is happening... what happens if a pci bus
mastering card makes a modification to this value?  sure, it normally
won't happen, but it can... and w/o the lock prefix, this CAN happen
from what I understand of the architecture...

so, it does have to lock even the memory bus, simply the cache isn't
enough for the lock to do what it needs...

-- 
  John-Mark Gurney                              Voice: +1 541 684 8449
  Cu Networking                                   P.O. Box 5693, 97405

  "The soul contains in itself the event that shall presently befall it.
  The event is only the actualizing of its thought." -- Ralph Waldo Emerson


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