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    SubjectRe: recv() hangs until SIGCHLD ?
    >> If there is data and the thread didn't wake up then that is a libc or 
    >> kernel problem;
    >> but if there is no data, then look for cases where earlier interrupted
    >> io actually
    >> consumed the data already or blame the sending process not the receiver.
    >> Also are the sockets blocking or non-blocking?
    > The sockets are non-blocking.

    Sorry, I made a spelling mistake here.

    I wanted to tell that the sockets ARE blocking (default behavior).

    > In a practical case, we have a thread blocked in recv() for more than 12
    > hours, which is way beyond the timeout of the sender connection. The
    > socket has already been closed by the sender so recv() should at least
    > be noticed and returns 0.

    To provide more informations :

    Doing a lsof on the receiver, we can see that it has several ESTABLISHED
    sockets connected to a given host/sender. Doing a lsof on the host does
    not give any socket connected to the receiver (since they have been
    closed due to a timeout).

    Also, the application correctly handles 0.
    The pseudo-code is the following :

    ret = recv()
    if( ret == -1 ) {
    if( errno == EINTR ) goto loop;
    return -1;
    return ret;

    Then, on the higher level, in case we get an error ( ret <= 0 ) then we
    close the socket.

    At first, we were using the libmysqlclient but since we had the bug with
    it we rewrote a mysql client so we can more easily check what's
    occurring. The same bug seems to occur with both implementations.


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      Last update: 2008-10-13 10:35    [W:0.020 / U:2.068 seconds]
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