//---
// gint:cpu:atomic - Simulated atomic operations
//---

#include <gint/cpu.h>

/* Value of IMASK when atomic mode is entered */
static int saved_IMASK = 0;
/* Number of atomic mode levels */
static unsigned int atomic_level = 0;

void cpu_atomic_start(void)
{
	/* There is no access problem to IMASK here because interrupts must
	   preserve and restore it */
	cpu_sr_t SR = cpu_getSR();
	cpu_sr_t SR2 = SR;
	SR2.IMASK = 15;
	cpu_setSR(SR2);

	/* Now that we're alone, atomically update the atomic level */
	if(atomic_level == 0) saved_IMASK = SR.IMASK;
	atomic_level++;
}

void cpu_atomic_end(void)
{
	cpu_sr_t SR = cpu_getSR();

	/* Update atomic_level before restoring interrupts */
	atomic_level--;
	if(atomic_level == 0) {
		SR.IMASK = saved_IMASK;
		saved_IMASK = 0;
	}

	cpu_setSR(SR);
}