415349575d
The full truth seems too complicated to write in this method's doc, so I'm going with a simple half truth. The full truth is that Fd returns the descriptor in blocking mode, because that is historically how it worked, and existing programs would be surprised if the descriptor is suddenly non-blocking. On Unix systems whether a file is non-blocking or not is a property of the underlying file description, not of a particular file descriptor, so changing the returned descriptor to blocking mode also changes the existing File to blocking mode. Blocking mode works fine, althoug I/O operations now take up a thread. SetDeadline and friends rely on the runtime poller, and the runtime poller only works if the descriptor is non-blocking. So it's correct that calling Fd disables SetDeadline. The other half of the truth is that if the program is willing to work with a non-blocking descriptor, it could call syscall.SetNonblock(descriptor, true) to change the descriptor, and the original File, to non-blocking mode. At that point SetDeadline would start working again. I tried to write that in a way that is short and comprehensible but failed. Since deadlines mostly work on pipes, and there isn't much reason to call Fd on a pipe, and few people use SetDeadline, I decided to punt. Fixes #22934 Change-Id: I2e49e036f0bcf71f5365193831696f9e4120527c Reviewed-on: https://go-review.googlesource.com/81636 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> |
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README.md
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