ref: aa8d3d79058ebcc5437e6d2f3d32d703cdac5c61
dir: /posix-arm/tas.c/
#include "u.h"
#include "libc.h"
int
tas(long *x)
{
int v, t, i = 1;
#if ARMv5
__asm__(
"swp %0, %1, [%2]"
: "=&r" (v)
: "r" (1), "r" (x)
: "memory"
);
#else
__asm__ (
"1: ldrex %0, [%2]\n"
" strex %1, %3, [%2]\n"
" teq %1, #0\n"
" bne 1b"
: "=&r" (v), "=&r" (t)
: "r" (x), "r" (i)
: "cc");
#endif
switch(v) {
case 0:
case 1:
return v;
default:
print("canlock: corrupted 0x%lux\n", v);
return 1;
}
}