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Date: Sun, 31 Aug 2008 15:38:01 +0200 From: Michael Noisternig <mnoist@...y.sbg.ac.at> To: linux-kernel@...r.kernel.org Subject: (more) epoll troubles 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) 0x9e6b8a8: read not avail (1460/2048 read) got EPOLLIN notification, read 1460 bytes again -> wait for another notification ...after a few minutes without any notification... 0x9e6b8a8: GOT RDHUP (2001:0/80002001:0) i.e. got notification for EPOLLRDHUP|EPOLLIN (2001), was waiting for EPOLLET|EPOLLRDHUP|EPOLLIN (80002001) 0x9e6b8a8: read not avail (342/2048 read) then on trying to read we find data in the buffer (???) 0x9e6b8a8: stored 16384 bytes this is the amount of data we expected to get /immediately/, i.e. without a minutes delay and rdhup Of course you might think that the other side sent the data only just before closing its side, but it is unlikely since we expected to get the 16384 bytes in one go (this is how that L7 protocol works), and I see this odd behaviour of missing input notifications now and then. Does anybody know/have an idea why I am missing EPOLLIN notifications? Any help is appreciated!!! Thanks in advance, Michael (please CC me when replying) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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