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/
/ int uts_lock ( int *p, int i );
/ Update the lock word pointed to by p with the
/ value i, using compare-and-swap.
/ Returns 0 if update was successful.
/ Returns 1 if update failed.
/
entry uts_lock
uts_lock:
using .,r15
st r2,8(sp) / Save R2
l r2,64+0(sp) / R2 -> word to update
slr r0, r0 / R0 = current lock value must be 0
l r1,64+4(sp) / R1 = new lock value
cs r0,r1,0(r2) / Try the update ...
be x / ... Success. Return 0
la r0,1 / ... Failure. Return 1
x: /
l r2,8(sp) / Restore R2
b 2(,r14) / Return to caller
drop r15
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