dec_if_positive
cat <<EOF
static __always_inline ${ret}
${arch}${atomic}_dec_if_positive(${atomic}_t *v)
{
${int} dec, c = ${arch}${atomic}_read(v);
do {
dec = c - 1;
if (unlikely(dec < 0))
break;
} while (!${arch}${atomic}_try_cmpxchg(v, &c, dec));
return dec;
}
EOF