Well, if someone can fix the latest gcc, which broke the VAX again, I could 
maybe look at this.

(But why do you want compare-and-swap? Why wouldn't compare-and-set suffice?)

	Johnny

Andrew Doran skrev:
> Hi,
> 
> We're nearly ready with atomic ops in the kernel, however the code for vax
> needs to be written. The minimum that needs to be provided is an atomic
> compare and swap function and the rest can be provided by C code.
> 
> There is already and atomic compare and _set_, for the reader/writer locks
> in lock_stubs.S. The description of how the CAS function should behave is
> below. It needs to be known by a few different names, this is from the arm
> port:
> 
> STRONG_ALIAS(_atomic_cas_ulong,_lock_cas)
> STRONG_ALIAS(atomic_cas_ulong,_lock_cas)
> STRONG_ALIAS(_atomic_cas_32,_lock_cas)
> STRONG_ALIAS(atomic_cas_32,_lock_cas)
> STRONG_ALIAS(_atomic_cas_uint,_lock_cas)
> STRONG_ALIAS(atomic_cas_uint,_lock_cas)
> STRONG_ALIAS(_atomic_cas_ptr,_lock_cas)
> STRONG_ALIAS(atomic_cas_ptr,_lock_cas)
> 
> Any takers?
> 
> Thanks,
> Andrew
> 
>      uint32_t
>      atomic_cas_32(volatile uint32_t *ptr, uint32_t old, uint32_t new);
> 
> DESCRIPTION
>      The atomic_cas family of functions perform a compare-and-swap operation
>      in an atomic fashion.  The value of the variable referenced by ptr is
>      compared against old.  If the values are equal, new is stored in the
>      variable referenced by ptr.
> 
>      The old value of the variable referenced by ptr is always returned
>      regardless of whether or not the new value was stored.  Applications can
>      test for success of the operation by comparing the return value to the
>      value passed as old; if they are equal then the new value was stored.


-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt@softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol