On 03.07.2011 17:00, Mikolaj Golub wrote:
Hi,
Hi Mikolaj,
Trying soreceive_stream I found that many applications (like firefox, pidgin,
gnus) might hang in soreceive_stream/sbwait.
Many thanks for testing soreceive_stream.
It was shown up that the issue was with O_NONBLOCK connections -- they blocked
in recv() when should not have been.
>
This can be checked with this simple test:
http://people.freebsd.org/~trociny/test_nonblock.c
In soreceive_stream we have the following code that looks wrong:
1968 /* Socket buffer is empty and we shall not block. */
1969 if (sb->sb_cc == 0&&
1970 ((sb->sb_flags& SS_NBIO) || (flags&
(MSG_DONTWAIT|MSG_NBIO)))) {
1971 error = EAGAIN;
1972 goto out;
1973 }
It should check so->so_state agains SS_NBIO, not sb->sb_flags. But just
Indeed.
changing this is not enough. This check is called too early -- before checking
that socket state is not SBS_CANTRCVMORE. As a result, if the peer closes the
connection recv() returns EAGAIN instead of 0. See this example:
http://people.freebsd.org/~trociny/test_close.c
So I moved the "nonblock" check below SBS_CANTRCVMORE check and ended up with
this patch:
http://people.freebsd.org/~trociny/uipc_socket.c.soreceive_stream.patch
It works for me fine.
OK.
Also, this part looks wrong:
1958 /* We will never ever get anything unless we are connected. */
1959 if (!(so->so_state& (SS_ISCONNECTED|SS_ISDISCONNECTED))) {
1960 /* When disconnecting there may be still some data
left. */
1961 if (sb->sb_cc> 0)
1962 goto deliver;
1963 if (!(so->so_state& SS_ISDISCONNECTED))
1964 error = ENOTCONN;
1965 goto out;
1966 }
Why we check in 1959 that state is not SS_ISDISCONNECTED? If it is valid then
the check at 1963 is useless becase it will be always true. Shouldn't it be
something like below?
>
if (!(so->so_state& (SS_ISCONNECTED|SS_ISCONNECTING))) {
/* When disconnecting there may be still some data left. */
if (sb->sb_cc> 0)
goto deliver;
error = ENOTCONN;
goto out;
}
(I don't see why we souldn't set ENOTCONN if the state is SS_ISDISCONNECTED).
ENOTCONN is only valid in the beginning of the connection. When we reach
SS_INDISCONNECTED the connection was connected before and we have to return
a 0-read to signal EOF. It can be simplified by immediately setting the
error and going out. The other cases can't ever be true.
Please try this patch:
http://people.freebsd.org/~andre/soreceive_stream.diff-20110707
I can't fully test it myself due to being 1000km from my development
machine and having only limited hw access for rebooting.
And the last :-). Currently, to try soreceive_stream one need to rebuild kernel
with TCP_SORECEIVE_STREAM and then set tunable net.inet.tcp.soreceive_stream.
Why do we need TCP_SORECEIVE_STREAM option? Wouldn't tunable be enough? It
would simplify trying soreceive_stream by users and we might have more
testing/feedback.
Done. See r223839.
--
Andre
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