in include/asm/spinlock.h [91:107]
static inline int arch_write_trylock(arch_rwlock_t *lock)
{
int temp;
__asm__ __volatile__(
" R6 = memw_locked(%1)\n"
" { %0 = #0; P3 = cmp.eq(R6,#0); R6 = #-1;}\n"
" { if (!P3) jump 1f; }\n"
" memw_locked(%1,P3) = R6;\n"
" %0 = P3;\n"
"1:\n"
: "=&r" (temp)
: "r" (&lock->lock)
: "memory", "r6", "p3"
);
return temp;
}