> Michael Noisternig wrote:
>> Hello,
>>
>> and sorry again if this is the wrong place to ask (again, please hint
>> to me to an appropriate place to ask in that case).
>>
>> After experimenting with epoll edge-triggered mode I am clueless why
>> on a few occassions I seem to not get any input notification despite
>> data is available.
>>
>> In detail: I have set up sockets with epoll events
>> EPOLLET|EPOLLRDHUP|EPOLLIN. When I get EPOLLIN for a socket, I read()
>> as long as I get what I asked for, i.e. whenever read() returns either
>> EAGAIN or less data than I asked for I take this as indication that I
>> must wait for another EPOLLIN notification. However, this does not
>> seem to work always.
>>
>> Here is some log from my program:
>>
>> 0x9e6b8a8: read not avail (1460/2048 read)
>> i.e. tried to read 2048 bytes, got 1460 -> assume must wait for
>> EPOLLIN for more data to read
>> (note that the fd is always in the epoll set with
>> EPOLLET|EPOLLRDHUP|EPOLLIN)
>
> It would likely be better to always continue trying to read until EAGAIN
> is returned, even if the read returned less than the requested amount,
> as implied here:
>
>
http://linux.die.net/man/7/epoll
>
> "The function do_use_fd() uses the new ready file descriptor until
> EAGAIN is returned by either read(2) or write(2). An event driven state
> machine application should, after having received EAGAIN, record its
> current state so that at the next call to do_use_fd() it will continue
> to read(2) or write(2) from where it stopped before. "
