diff --git a/cloudvolume/datasource/precomputed/image/common.py b/cloudvolume/datasource/precomputed/image/common.py
index 5250308f..9f9f1360 100644
--- a/cloudvolume/datasource/precomputed/image/common.py
+++ b/cloudvolume/datasource/precomputed/image/common.py
@@ -63,12 +63,17 @@ def parallel_execution(
 ):
   global error_queue
 
-  error_queue = mp.Queue()
-  progress_queue = mp.Queue()
-  fs_lock = mp.Lock()
+  # Ensure processes do not accidentally inherit
+  # locks from forking and deadlock. Instead launch
+  # new interpreters.
+  ctx = mp.get_context("spawn")
+
+  error_queue = ctx.Queue()
+  progress_queue = ctx.Queue()
+  fs_lock = ctx.Lock()
 
   if parallel is True:
-    parallel = mp.cpu_count()
+    parallel = ctx.cpu_count()
   elif parallel <= 0:
     raise ValueError(f"Parallel must be a positive number or boolean (True: all cpus). Got: {parallel}")
 
@@ -104,11 +109,6 @@ def cleanup(signum, frame):
       )
       proc.start()
 
-    # Ensure processes do not accidentally inherit
-    # locks from forking and deadlock. Instead launch
-    # new interpreters.
-    ctx = mp.get_context("spawn")
-
     with concurrent.futures.ProcessPoolExecutor(
       max_workers=parallel,
       initializer=initialize_synchronization,
diff --git a/cloudvolume/datasource/precomputed/image/rx.py b/cloudvolume/datasource/precomputed/image/rx.py
index fdd5004a..ba90b0b2 100644
--- a/cloudvolume/datasource/precomputed/image/rx.py
+++ b/cloudvolume/datasource/precomputed/image/rx.py
@@ -562,6 +562,7 @@ def process(src_img, src_bbox):
     green=green, secrets=secrets, background_color=background_color
   )
 
+  del dest_img
   array_like.close()
 
   return len(cloudpaths)
diff --git a/cloudvolume/datasource/precomputed/image/tx.py b/cloudvolume/datasource/precomputed/image/tx.py
index 3c361a8d..f7dca21d 100644
--- a/cloudvolume/datasource/precomputed/image/tx.py
+++ b/cloudvolume/datasource/precomputed/image/tx.py
@@ -205,17 +205,19 @@ def upload_aligned(
     secrets=secrets
   )
 
-  parallel_execution(
-    cup, chunk_ranges, parallel, 
-    progress, desc="Upload", 
-    cleanup_shm=location
-  )
-
-  # If manual mode is enabled, it's the 
-  # responsibilty of the user to clean up
-  if not use_shared_memory:
-    array_like.close()
-    shm.unlink(location)
+  try:
+    parallel_execution(
+      cup, chunk_ranges, parallel, 
+      progress, desc="Upload", 
+      cleanup_shm=location
+    )
+  finally:
+    # If manual mode is enabled, it's the 
+    # responsibilty of the user to clean up
+    if not use_shared_memory:
+      del renderbuffer
+      array_like.close()
+      shm.unlink(location)
 
 def child_upload_process(
     meta, cache, 
@@ -267,6 +269,7 @@ def updatefn():
       secrets=secrets,
     )
   finally:
+    del renderbuffer
     array_like.close()
 
 def threaded_upload_chunks(
diff --git a/cloudvolume/frontends/precomputed.py b/cloudvolume/frontends/precomputed.py
index 8d3f7bba..a1cb8a34 100644
--- a/cloudvolume/frontends/precomputed.py
+++ b/cloudvolume/frontends/precomputed.py
@@ -1127,6 +1127,8 @@ def upload_from_shared_memory(self, location, bbox, order='F', cutout_bbox=None)
       order=order,
       use_shared_memory=True,
     )
+    del cutout_image
+    del shared_image
     mmap_handle.close()
 
   def upload_from_file(self, location, bbox, order='F', cutout_bbox=None):
@@ -1188,6 +1190,7 @@ def upload_from_file(self, location, bbox, order='F', cutout_bbox=None):
       order=order,
       use_file=True,
     )
+    del shared_image
     mmap_handle.close()
 
   def viewer(self, port=1337):
diff --git a/cloudvolume/sharedmemory.py b/cloudvolume/sharedmemory.py
index 79aaee56..35efb8d2 100644
--- a/cloudvolume/sharedmemory.py
+++ b/cloudvolume/sharedmemory.py
@@ -127,8 +127,7 @@ def allocate_shm_file(filename, nbytes, dbytes, readonly):
 
 def ndarray_shm(shape, dtype, location, readonly=False, order='F', **kwargs):
   """Create a shared memory numpy array. Requires /dev/shm to exist."""
-  import posix_ipc
-  from posix_ipc import O_CREAT
+  from multiprocessing import shared_memory
   import psutil
 
   nbytes = Vec(*shape).rectVolume() * np.dtype(dtype).itemsize
@@ -170,21 +169,26 @@ def ndarray_shm(shape, dtype, location, readonly=False, order='F', **kwargs):
   # a threading condition where the condition of the shared memory
   # was adjusted between the check above and now. Better to make sure
   # that we don't accidently change anything if readonly is set.
-  flags = 0 if readonly else O_CREAT 
   size = 0 if readonly else int(nbytes) 
+  create = (not readonly) and (not preexisting)
 
   try:
-    shared = posix_ipc.SharedMemory(location, flags=flags, size=size)
-    array_like = mmap.mmap(shared.fd, shared.size)
-    os.close(shared.fd)
-    renderbuffer = np.ndarray(buffer=array_like, dtype=dtype, shape=shape, order=order, **kwargs)
+    shm = shared_memory.SharedMemory(name=location, create=create, size=size)
+    renderbuffer = np.frombuffer(buffer=shm.buf, dtype=dtype)
+    renderbuffer = renderbuffer.reshape(shape, order=order)
+  except FileExistsError:
+    if not readonly:
+      raise
+    shm = shared_memory.SharedMemory(name=location, create=False, size=size)
+    renderbuffer = np.frombuffer(buffer=shm.buf, dtype=dtype)
+    renderbuffer = renderbuffer.reshape(shape, order=order)
   except OSError as err:
     if err.errno == errno.ENOMEM: # Out of Memory
-      posix_ipc.unlink_shared_memory(location)      
+      unlink_shm(location)
     raise
 
   renderbuffer.setflags(write=(not readonly))
-  return array_like, renderbuffer
+  return shm, renderbuffer
 
 def unlink(location):
   if EMULATE_SHM:
@@ -192,10 +196,11 @@ def unlink(location):
   return unlink_shm(location)
 
 def unlink_shm(location):
-  import posix_ipc
+  from multiprocessing import shared_memory
   try:
-    posix_ipc.unlink_shared_memory(location)
-  except posix_ipc.ExistentialError:
+    shm = shared_memory.SharedMemory(name=location, create=False)
+    shm.unlink()
+  except FileNotFoundError:
     return False
   return True
 
diff --git a/setup.py b/setup.py
index 6e23ea6f..ae506f54 100644
--- a/setup.py
+++ b/setup.py
@@ -56,7 +56,6 @@ def requirements():
       "blosc",
     ],
     ':sys_platform!="win32"': [
-      "posix_ipc>=1.0.4",
       "psutil>=5.4.3",
     ],
     "mesh_viewer": [ 'vtk' ],
diff --git a/test/test_cloudvolume.py b/test/test_cloudvolume.py
index 5bfa25ff..78fa327f 100644
--- a/test/test_cloudvolume.py
+++ b/test/test_cloudvolume.py
@@ -470,6 +470,7 @@ def test_parallel_shared_memory_write():
   assert np.all(cv[0,0,:] == 1)
   assert np.all(cv[1,0,:] == 0)
 
+  del shareddata
   mmapfh.close()
   shm.unlink(shm_location)
 
diff --git a/test/test_sharedmemory.py b/test/test_sharedmemory.py
index e1a61a90..3d93cfc1 100644
--- a/test/test_sharedmemory.py
+++ b/test/test_sharedmemory.py
@@ -68,10 +68,12 @@ def test_ndarray_sh():
 	array_like, array = shm.ndarray_shm(shape=(2,2,2), dtype=np.uint8, location=location)
 	assert np.all(array == np.zeros(shape=(2,2,2), dtype=np.uint8))
 	array[:] = 100
+	del array
 	array_like.close()
 
 	array_like, array = shm.ndarray_shm(shape=(2,2,2), dtype=np.uint8, location=location)
 	assert np.all(array[:] == 100)
+	del array
 	array_like.close()
 
 	filename = os.path.join(shm.SHM_DIRECTORY, location)
@@ -86,7 +88,9 @@ def test_ndarray_sh():
 
 	available = psutil.virtual_memory().available
 	array_like, array = shm.ndarray_shm(shape=(available // 10,2,2), dtype=np.uint8, location=location)
+	del array
 	array_like.close()
+	
 	try:
 		array_like, array = shm.ndarray_shm(shape=(available,2,2), dtype=np.uint8, location=location)
 		assert False
@@ -109,5 +113,7 @@ def test_ndarray_sh():
 	except shm.SharedMemoryReadError:
 		pass
 
+	del array
+	array_like.close()
 	assert shm.unlink_shm(location) == True
 	assert shm.unlink_shm(location) == False