Re: GCD cancel handler invocation
Re: GCD cancel handler invocation
- Subject: Re: GCD cancel handler invocation
- From: Dave Zarzycki <email@hidden>
- Date: Mon, 10 Jan 2011 14:20:56 -0800
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.
davez_______________________________________________
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