On Jan 10, 2011, at 2:58 PM, Ken Thomases wrote: > On Jan 10, 2011, at 4:20 PM, Dave Zarzycki wrote: > >> On Jan 10, 2011, at 2:06 PM, Jonathon Kuo wrote: >> >>> I set up a source handler on a TCP socket like this: >>> dispatch_source_t newsrc = >>> dispatch_source_create(DISPATCH_SOURCE_TYPE_READ,sockfd,0,globalQueue); >>> >>> It works well, and when a client process closes his socket my >>> cancel_handler gets called, I clean up, and life is good. But if I do a >>> close(sockfd) from my side, my cancel_handler doesn't get invoked. I have >>> to explicitly do a dispatch_source_cancel(). Shouldn't closing the socket >>> be enough to cause my cancel_handler to be run? >> >> Jonathon, >> >> No. This is covered in the dispatch_source_create() man page under the >> section on cancelation: >> >> Important: a cancellation handler is required for file descriptor and mach >> port based sources in order to safely close the descriptor or destroy the >> port. Closing the descriptor or port before the cancellation handler has run >> may result in a race condition: if a new descriptor is allocated with the >> same value as the recently closed descriptor while the source's event >> handler is still running, the event handler may read/write data to the wrong >> descriptor. > > And, likewise, it is not safe to close a file descriptor in one thread while > it is the subject of a read(), select(), kevent(), or similar in another > thread. In other words, in no system API is it safe to do what you're trying > to do.
Okay... then is the only place I should ever call the close() is from within the cancel_handler for that file descriptor? _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
