var n int
	systemstack(func() {
		var u unwinder
		u.initAt(pc, sp, 0, gp, unwindSilentErrors)
		n = tracebackPCs(&u, skip, pcbuf)
	})
	return n
}

func gcallers(gp *g, skip int, pcbuf []uintptr) int {
	var u unwinder
	u.init(gp, unwindSilentErrors)
	return tracebackPCs(&u, skip, pcbuf)
}

// showframe reports whether the frame with the given characteristics should

	}

	var nstk int
	gp := getg()
	sp := getcallersp()
	pc := getcallerpc()
	systemstack(func() {
		var u unwinder
		u.initAt(pc, sp, 0, gp, unwindSilentErrors|unwindJumpStack)
		nstk = 1 + tracebackPCs(&u, skip, prof.stack[1:])
	})
	if nstk < len(prof.stack) {
		prof.stack[nstk] = 0
	}
}

func (prof *mLockProfile) store() {
	// Report any contention we experience within this function as "lost"; it's

	MOVQ	(g_sched+gobuf_bp)(AX), BP
	MOVQ	$0, (g_sched+gobuf_sp)(AX)
	MOVQ	$0, (g_sched+gobuf_bp)(AX)
	RET

noswitch:
	// already on m stack; tail call the function
	// Using a tail call here cleans up tracebacks since we won't stop
	// at an intermediate systemstack.
	MOVQ	DI, DX
	MOVQ	0(DI), DI
	// The function epilogue is not called on a tail call.
	// Pop BP from the stack to simulate it.
	POPQ	BP
	JMP	DI