On 09/22/2015 01:55 AM, Junio C Hamano wrote:
Stefan Beller <sbel...@google.com> writes:
So if we get an EAGAIN or EWOULDBLOCK error the fd must be nonblocking.
As the intend of xread is to read as much as possible either until the
fd is EOF or an actual error occurs, we can ease the feeder of the fd
by not spinning the whole time, but rather wait for it politely by not
busy waiting.
As you said in the cover letter, this does look questionable. It is
sweeping the problem under the rug (the hard-coded 100ms is a good
clue to tell that). If the caller does want us to read thru to the
end, then we would need to make it easier for such a caller to stop
marking the file descriptor to be non-blocking, but this does not do
anything to help that. An alternative might be to automatically
turn nonblocking off temporarily once we get EAGAIN (and turn it on
again before leaving); that would be an approach to make it
unnecessary to fix the caller (which has its own set of problems,
though).
Wouldn' that function be somewhat mis-named and/or mis-behaved?
read_in_full_with_hard_coded_timeout_and_fix_O_NONBLOCK()
could make sure that the user of this function knows what's going on
under the hood.
More seriously, if someone calls xread() with a non-blocking socket,
the caller wants to return and does want to his own timeout handling.
If we want to have a timeouted read(), we can call it
xread_timout(int fd, voxread(int fd, void *buf, size_t len, int timeout)
(Or something similar) to make clear that there is an underlying
timeout handling.
Another option could be to name the function
read_in_full_timeout().
But in any case I suggest to xread() as it is, and not to change the
functionality
behind the back of the users.
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