}

// SpanAlloc records an event indicating that the span has just been allocated.
func (tl traceLocker) SpanAlloc(s *mspan) {
	tl.eventWriter(traceGoRunning, traceProcRunning).commit(traceEvSpanAlloc, traceSpanID(s), traceArg(s.npages), traceSpanTypeAndClass(s))
}

// SpanFree records an event indicating that the span is about to be freed.
func (tl traceLocker) SpanFree(s *mspan) {

	if span.list != list {
		print("runtime: failed mSpanList.remove span.npages=", span.npages,
			" span=", span, " prev=", span.prev, " span.list=", span.list, " list=", list, "\n")
		throw("mSpanList.remove")
	}
	if list.first == span {
		list.first = span.next
	} else {
		span.prev.next = span.next
	}
	if list.last == span {
		list.last = span.prev
	} else {
		span.next.prev = span.prev

//go:build !openbsd

package runtime

// osStackAlloc performs OS-specific initialization before s is used
// as stack memory.
func osStackAlloc(s *mspan) {
}

// osStackFree undoes the effect of osStackAlloc before s is returned
// to the heap.
func osStackFree(s *mspan) {

	return s
}

// Return span from an mcache.
//
// s must have a span class corresponding to this
// mcentral and it must not be empty.
func (c *mcentral) uncacheSpan(s *mspan) {
	if s.allocCount == 0 {
		throw("uncaching span but s.allocCount == 0")
	}

	sg := mheap_.sweepgen
	stale := s.sweepgen == sg+1

	// Fix up sweepgen.
	if stale {
		// Span was cached before sweep began. It's our

	h.u.Store(0)
}

// atomicMSpanPointer is an atomic.Pointer[mspan]. Can't use generics because it's NotInHeap.
type atomicMSpanPointer struct {
	p atomic.UnsafePointer
}

// Load returns the *mspan.
func (p *atomicMSpanPointer) Load() *mspan {
	return (*mspan)(p.p.Load())
}

// Store stores an *mspan.
func (p *atomicMSpanPointer) StoreNoWB(s *mspan) {
	p.p.StoreNoWB(unsafe.Pointer(s))

		throw("mspan.sweep: m is not locked")
	}

	s := sl.mspan
	if !preserve {
		// We'll release ownership of this span. Nil it out to
		// prevent the caller from accidentally using it.
		sl.mspan = nil
	}

	sweepgen := mheap_.sweepgen
	if state := s.state.get(); state != mSpanInUse || s.sweepgen != sweepgen-1 {

	span.ensureSwept()
	KeepAlive(ptr) // make sure ptr is still alive after span is swept

	objIndex := span.objIndex(uintptr(ptr))

	lock(&span.speciallock) // guard against concurrent calls of setPinned on same span

	pinnerBits := span.getPinnerBits()
	if pinnerBits == nil {
		pinnerBits = span.newPinnerBits()
		span.setPinnerBits(pinnerBits)
	}
	pinState := pinnerBits.ofObject(objIndex)
	if pin {

		rzSize := computeRZlog(span.elemsize)
		span.elemsize -= rzSize
		span.largeType.Size_ = span.elemsize
		rzStart := span.base() + span.elemsize
		span.userArenaChunkFree = makeAddrRange(span.base(), rzStart)
		asanpoison(unsafe.Pointer(rzStart), span.limit-rzStart)
		asanunpoison(unsafe.Pointer(span.base()), span.elemsize)
	}

	if rate := MemProfileRate; rate > 0 {
		c := getMCache(mp)
		if c == nil {

	}
	return tp
}

// objBase returns the base pointer for the object containing addr in span.
//
// Assumes that addr points into a valid part of span (span.base() <= addr < span.limit).
//
//go:nosplit
func (span *mspan) objBase(addr uintptr) uintptr {
	return span.base() + span.objIndex(addr)*span.elemsize
}

// bulkBarrierPreWrite executes a write barrier

}

//go:nosplit
func validSIGPROF(mp *m, c *sigctxt) bool {
	return true
}

func osStackAlloc(s *mspan) {
	osStackRemap(s, _MAP_STACK)
}

func osStackFree(s *mspan) {
	// Undo MAP_STACK.
	osStackRemap(s, 0)
}

func osStackRemap(s *mspan, flags int32) {
	a, err := mmap(unsafe.Pointer(s.base()), s.npages*pageSize, _PROT_READ|_PROT_WRITE, _MAP_PRIVATE|_MAP_ANON|_MAP_FIXED|flags, -1, 0)