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Date: Tue, 26 Aug 2008 19:25:22 +0200 From: Michael Noisternig <mnoist@...y.sbg.ac.at> To: linux-kernel@...r.kernel.org Subject: (e)poll and (rd)hup questions Hello folks, I hope this is a right place to ask this question. (Sorry if it isn't, please hint me where to post in that case.) This has been bugging me for quite some while now. I'm using epoll in default level-triggered mode. I'm polling for input, output, rdhup, and forcibly for hup. I figured that when I get EPOLLRDHUP that doesn't mean there is no more data to read, presumably I must empty the kernel buffer by continously reading from the fd until I get zero as a result indicating rdhup. This means EPOLLRDHUP is delivered asynchronously and thus is pretty useless to me. On the other hand, EPOLLHUP seems to be delivered synchronously. If it isn't then this means I get constantly notified about a closed fd until I have read all data from the kernel buffer and remove the fd from the epoll set (which makes being forced to hup notifications useless to me). (And no, don't tell me to use edge-triggered mode, I have reasons to use level-triggered.) Question: Is my observation correct that EPOLLRDHUP is delivered asynchronously in contrast to EPOLLHUP? Or is EPOLLHUP delivered asynchronously as well? Thanks, anwers would help a lot!!! Michael -- 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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