Fork: function not implemented

Hi ,
I code a distributed data parallel in pytorch (windows 10) , everything goes fine without error . When I load it in Linux , it give me and error “runtime error: fork: function not implemented”.
This is how I code it

I used

for machine_rank in range(world_size):
mp.spawn( train,args=(world_size,backend,c_param),nprocs=world_size,join=True)

then follow by:

def train(*args):
if (args[3].training_type==1):
init_method=r"file:///" +args[3].classifier+".log",
rank=args[0] )

I suspect the problem is in join=True in mp.spawn

any help will be much appreciated