heap[len(heap)-1].ev.time = 21
	heapUpdate(heap, len(heap)-1)
	checkHeap(t, heap)
	if heap[len(heap)-1].ev.time != 21 {
		t.Fatalf("heap update failed, expected %d as heap min: %s", 21, heapDebugString(heap))
	}

	// Update the last element to be smaller.
	heap[len(heap)-1].ev.time = 7
	heapUpdate(heap, len(heap)-1)
	checkHeap(t, heap)
	if heap[len(heap)-1].ev.time == 21 {

	type X struct {
		buf     [1]byte
		nextbuf []byte
		next    *X
	}
	var head *X
	for i := 0; i < 10; i++ {
		p := &X{}
		p.buf[0] = 42
		p.next = head
		if head != nil {
			p.nextbuf = head.buf[:]
		}
		head = p
		runtime.GC()
	}
	for p := head; p != nil; p = p.next {
		if p.buf[0] != 42 {
			t.Fatal("corrupted heap")
		}
	}
}

func TestGcRescan(t *testing.T) {
	type X struct {

logo-teal.png...

logo-teal.svg...

	if p < s.stack.lo || p >= s.stack.hi {
		throw("address not a stack address")
	}
	head := &s.buf
	if conservative {
		head = &s.cbuf
	}
	buf := *head
	if buf == nil {
		// Initial setup.
		buf = (*stackWorkBuf)(unsafe.Pointer(getempty()))
		buf.nobj = 0
		buf.next = nil
		*head = buf
	} else if buf.nobj == len(buf.obj) {
		if s.freeBuf != nil {
			buf = s.freeBuf
			s.freeBuf = nil

	return true
}

// mProf_NextCycle publishes the next heap profile cycle and creates a
// fresh heap profile cycle. This operation is fast and can be done
// during STW. The caller must call mProf_Flush before calling
// mProf_NextCycle again.
//
// This is called by mark termination during STW so allocations and
// frees after the world is started again count towards a new heap
// profiling cycle.
func mProf_NextCycle() {

logo-teal-vector.svg...

	// Try directly allocating from the current head arena.
	head := (*gcBitsArena)(atomic.Loadp(unsafe.Pointer(&gcBitsArenas.next)))
	if p := head.tryAlloc(bytesNeeded); p != nil {
		return p
	}

	// There's not enough room in the head arena. We may need to
	// allocate a new arena.
	lock(&gcBitsArenas.lock)
	// Try the head arena again, since it may have changed. Now

logo-teal-vector.svg...

	// (3) Group each event batch by M, sorted by timestamp. (batchCursor contains the groups.)
	// (4) Organize batchCursors in a min-heap, ordered by the timestamp of the next event for each M.
	// (5) Try to advance the next event for the M at the top of the min-heap.
	//   (a) On success, select that M.
	//   (b) On failure, sort the min-heap and try to advance other Ms. Select the first M that advances.
	//   (c) If there's nothing left to advance, goto (1).