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