Messages in this thread Patch in this message | | | Date | Fri, 24 Sep 2010 09:23:59 -0700 | From | Greg KH <> | Subject | [11/80] tcp: select(writefds) dont hang up when a peer close connection |
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2.6.35-stable review patch. If anyone has any objections, please let us know.
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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
[ Upstream commit d84ba638e4ba3c40023ff997aa5e8d3ed002af36 ]
This issue come from ruby language community. Below test program hang up when only run on Linux.
% uname -mrsv Linux 2.6.26-2-486 #1 Sat Dec 26 08:37:39 UTC 2009 i686 % ruby -rsocket -ve ' BasicSocket.do_not_reverse_lookup = true serv = TCPServer.open("127.0.0.1", 0) s1 = TCPSocket.open("127.0.0.1", serv.addr[1]) s2 = serv.accept s2.close s1.write("a") rescue p $! s1.write("a") rescue p $! Thread.new { s1.write("a") }.join' ruby 1.9.3dev (2010-07-06 trunk 28554) [i686-linux] #<Errno::EPIPE: Broken pipe> [Hang Here]
FreeBSD, Solaris, Mac doesn't. because Ruby's write() method call select() internally. and tcp_poll has a bug.
SUS defined 'ready for writing' of select() as following.
| A descriptor shall be considered ready for writing when a call to an output | function with O_NONBLOCK clear would not block, whether or not the function | would transfer data successfully.
That said, EPIPE situation is clearly one of 'ready for writing'.
We don't have read-side issue because tcp_poll() already has read side shutdown care.
| if (sk->sk_shutdown & RCV_SHUTDOWN) | mask |= POLLIN | POLLRDNORM | POLLRDHUP;
So, Let's insert same logic in write side.
- reference url http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/31065 http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/31068
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> --- net/ipv4/tcp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -453,7 +453,8 @@ unsigned int tcp_poll(struct file *file, if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)) mask |= POLLOUT | POLLWRNORM; } - } + } else + mask |= POLLOUT | POLLWRNORM; if (tp->urg_data & TCP_URG_VALID) mask |= POLLPRI;
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