// Use of this source file is governed by a BSD-style
// license that can be found in the LICENSE file.`

#include "runtime.h"
#include "defs.h"
#include "signals.h"
#include "os.h"

// FreeBSD's umtx_op syscall is effectively the same as Linux's futex, and
// thus the code is largely similar. See linux/thread.c for comments.

static void
umtx_wait(uint32 *addr, uint32 val)
{
	int32 ret;

	ret = sys_umtx_op(addr, UMTX_OP_WAIT, val, nil, nil);
	if(ret >= 0 || ret == -EINTR)
		return;

	printf("umtx_wait addr=%p val=%d ret=%d\n", addr, val, ret);
	*(int32*)0x1005 = 0x1005;
}

static void
umtx_wake(uint32 *addr)
{
	int32 ret;

	ret = sys_umtx_op(addr, UMTX_OP_WAKE, 1, nil, nil);
	if(ret >= 0)
		return;

	printf("umtx_wake addr=%p ret=%d\n", addr, ret);
	*(int32*)0x1006 = 0x1006;
}

// See linux/thread.c for comments about the algorithm.
static void
umtx_lock(Lock *l)
{
	uint32 v;

again:
	v = l->key;
	if((v&1) == 0){
		if(cas(&l->key, v, v|1))
			return;
		goto again;
	}

	if(!cas(&l->key, v, v+2))
		goto again;

	umtx_wait(&l->key, v+2);

	for(;;){
		v = l->key;
		if(v < 2)
			throw("bad lock key");
		if(cas(&l->key, v, v-2))
			break;
	}

	goto again;
}

static void
umtx_unlock(Lock *l)
{
	uint32 v;

again:
	v = l->key;
	if((v&1) == 0)
		throw("unlock of unlocked lock");
	if(!cas(&l->key, v, v&~1))
		goto again;

	if(v&~1)
		umtx_wake(&l->key);
}

void
lock(Lock *l)
{
	if(m->locks < 0)
		throw("lock count");
	m->locks++;
	umtx_lock(l);
}

void 
unlock(Lock *l)
{
	m->locks--;
	if(m->locks < 0)
		throw("lock count");
	umtx_unlock(l);
}

// Event notifications.
void
noteclear(Note *n)
{
	n->lock.key = 0;
	umtx_lock(&n->lock);
}

void
notesleep(Note *n)
{
	umtx_lock(&n->lock);
	umtx_unlock(&n->lock);
}

void
notewakeup(Note *n)
{
	umtx_unlock(&n->lock);
}

void thr_start(void*);

void
newosproc(M *m, G *g, void *stk, void (*fn)(void))
{
	ThrParam param;

	USED(fn);	// thr_start assumes fn == mstart
	USED(g);	// thr_start assumes g == m->g0

	if(0){
		printf("newosproc stk=%p m=%p g=%p fn=%p id=%d/%d ostk=%p\n",
			stk, m, g, fn, m->id, m->tls[0], &m);
	}

	runtime_memclr((byte*)&param, sizeof param);

	param.start_func = thr_start;
	param.arg = m;
	param.stack_base = stk;
	param.stack_size = g->stackbase - g->stackguard + 256;
	param.child_tid = (intptr*)&m->procid;
	param.parent_tid = nil;
	param.tls_base = (int8*)&m->tls[0];
	param.tls_size = sizeof m->tls;

	m->tls[0] = m->id;	// so 386 asm can find it

	thr_new(&param, sizeof param);
}

void
osinit(void)
{
}

// Called to initialize a new m (including the bootstrap m).
void
minit(void)
{
	// Initialize signal handling
	m->gsignal = malg(32*1024);
	signalstack(m->gsignal->stackguard, 32*1024);
}