问无法在大队列多处理上使用join -Python

EN

#Each pic's size is 1280x720 
import time

from multiprocessing import Process,JoinableQueue,Queue,Value

**def create_row(M, q_row,y_val):**    #creating lines. len:720 len of each     

    line_len=720
    col_len=1280

    for i in range(line_len):
       q_row.put(M[(i*col_len):((i+1)*col_len)])


**def create_col(M, q_col,x_val):** #creating cols

    col_len=1280  
    line_len=720

    for i in range(col_len): 
        l = list() 
        for j in range(line_len):
            l.append(M[j*line_len + i])    
        q_col.put(l)

**def main():**

    #creating row and col Queue
    q_row=JoinableQueue()
    q_col=JoinableQueue()

    x_val=Value('i',-1)
    y_val=Value('i',-1)

    p1=Process(target=create_row,args=(M,q_row,y_val))
    p2=Process(target=create_col,args=(M,q_col,x_val))
    q_row.join()
    q_col.join()
    p1.start()
    p2.start()
    p1.join()
    p2.join()