Bryan Olson wrote: > Carl J. Van Arsdall wrote: > >> Steve Horsley wrote: >> >> >>> [EMAIL PROTECTED] wrote: >>> >>> >>> >>>> thread1: >>>> while 1: >>>> buf = s.read() >>>> process(buf) >>>> >>>> thread2: >>>> while 1: >>>> buf = getdata() >>>> s.write(buf) >>>> >>> It is safe, but watch out for this gotcha: If thread B calls s.close() >>> while thread A is blocked in s.read(), thread A will never return from >>> the read. My preferred solution is to set socket timeout to a few >>> seconds, and loop checking a status flag so I know when to quit. >>> > > Certainly one needs timeouts to avoid hanging should the remote > side stop. Sockets don't have a read() method, and hanging on > recv() doesn't seem to have anything to do with close(). > > I didn't find any definitive doc, so I tested using Python > sockets on Linux (Debian/Ubuntu current) and WinXP. A recv() > started before the close() will block/return just as if > close() were never called. The close() neither triggers recv() > to abort, nor prevents it from receiving data and detecting > shutdown. > > > >> I think a better thing would be to use something like a condition object >> to tie the two threads together and not use any polling loops. >> >> i.e. consumer goes to sleep while data buffer is empty, producer >> produces and signals condition object, consumer wakes up and consumes. >> > > I can infer two producer-consumer relationships from the example, > but they don't allow a condition object; the writer's consumer and > the reader's producer are on the remote end of the socket. The > socket will already handle the blocking and wake-up. > > >> To take this a step further, you have a status flag that is set to >> something like QUIT or CONSUME and when the condition is triggered wake >> up, then examine the status flag to determine if the consumer should >> then quit, consume, or whatever else you'd want your consumer thread to do. >> > > What problem are you trying to solve? Normal socket sending, receiving, > and shutdown discipline work fine. When the writer is done writing, it > should call sock.shutdown(socket.SHUT_WR). When the reader gets zero > bytes from recv(nonzero), that means the remote end has finished > writing, so the reader may call sock.shutdown(socket.SHUT_RD). > Doh! I read the word threads and got carried away not even realizing sockets. Well, looks like today i'll just have to remember to drink my coffee
:-D -c -- Carl J. Van Arsdall [EMAIL PROTECTED] Build and Release MontaVista Software -- http://mail.python.org/mailman/listinfo/python-list
