// OpenBSD.
	physPageAlignedStacks = GOOS == "openbsd"
)

// Main malloc heap.
// The heap itself is the "free" and "scav" treaps,
// but all the other global data is here too.
//
// mheap must not be heap-allocated because it contains mSpanLists,
// which must not be heap-allocated.
type mheap struct {
	_ sys.NotInHeap

	// lock must only be acquired on the system stack, otherwise a g

stackLarge,
  stackpool,
  wbufSpans
# Above mheap is anything that can call the span allocator.
< mheap;
# Below mheap is the span allocator implementation.
#
# Specials: we're allowed to allocate a special while holding
# an mspanSpecial lock, and they're part of the malloc implementation.
# Pinner bits might be freed by the span allocator.
mheap, mspanSpecial < mheapSpecial;
mheap, mheapSpecial < globalAlloc;

}

func main() {
}

/* Before fix:

invalid m->locked = 2
fatal error: internal lockOSThread error

goroutine 2 [runnable]:
runtime.MHeap_Scavenger()
	/Users/rsc/g/go/src/pkg/runtime/mheap.c:438
runtime.goexit()
	/Users/rsc/g/go/src/pkg/runtime/proc.c:1313
created by runtime.main
	/Users/rsc/g/go/src/pkg/runtime/proc.c:165

goroutine 3 [runnable]:
main.func·002()

				releasedEager := mheap_.pages.scav.releasedEager.Load()

				// Print the line.
				printScavTrace(releasedBg, releasedEager, false)

				// Update the stats.
				mheap_.pages.scav.releasedBg.Add(-releasedBg)
				mheap_.pages.scav.releasedEager.Add(-releasedEager)
				unlock(&mheap_.lock)
			})
		}
		scavenger.ready()
	}

	gp.m.locks--
	return npages
}

			a, size := sysReserveAligned(unsafe.Pointer(p), arenaSize, heapArenaBytes)
			if a != nil {
				mheap_.arena.init(uintptr(a), size, false)
				p = mheap_.arena.end // For hint below
				break
			}
		}
		hint := (*arenaHint)(mheap_.arenaHintAlloc.alloc())
		hint.addr = p
		hint.next, mheap_.arenaHints = mheap_.arenaHints, hint

		// Place the hint for user arenas just after the large reservation.
		//

			c.fullSwept(sg).push(s)
		}
	}
}

// grow allocates a new empty span from the heap and initializes it for c's size class.
func (c *mcentral) grow() *mspan {
	npages := uintptr(class_to_allocnpages[c.spanclass.sizeclass()])
	size := uintptr(class_to_size[c.spanclass.sizeclass()])

	s := mheap_.alloc(npages, c.spanclass)
	if s == nil {
		return nil
	}

// Each chunk must be a multiple of the heap arena size, or the heap arena size must
// be divisible by the arena chunks. The address space for each chunk, and each
// corresponding heapArena for that address space, are eternally reserved for use as
// arena chunks. That is, they can never be used for the general heap. Each chunk
// is also represented by a single mspan, and is modeled as a single large heap

	lockRankGscan:           "gscan",
	lockRankStackpool:       "stackpool",
	lockRankStackLarge:      "stackLarge",
	lockRankHchanLeaf:       "hchanLeaf",
	lockRankWbufSpans:       "wbufSpans",
	lockRankMheap:           "mheap",
	lockRankMheapSpecial:    "mheapSpecial",
	lockRankGlobalAlloc:     "globalAlloc",
	lockRankTrace:           "trace",
	lockRankTraceStackTab:   "traceStackTab",
	lockRankPanic:           "panic",

// time, but may take time proportional to the size of the mapped heap beyond that.
//
// The heap lock must not be held over this operation, since it will briefly acquire
// the heap lock.
//
// Must be called on the system stack because it acquires the heap lock.
//
//go:systemstack
func (p *pageAlloc) enableChunkHugePages() {
	// Grab the heap lock to turn on huge pages for new chunks and clone the current

		t.FailNow()
	}
}

type acLink struct {
	x [1 << 20]byte
}

var arenaCollisionSink []*acLink

func TestArenaCollision(t *testing.T) {
	testenv.MustHaveExec(t)

	// Test that mheap.sysAlloc handles collisions with other
	// memory mappings.
	if os.Getenv("TEST_ARENA_COLLISION") != "1" {
		cmd := testenv.CleanCmdEnv(exec.Command(os.Args[0], "-test.run=^TestArenaCollision$", "-test.v"))