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Date: Mon, 20 Oct 2008 10:25:10 +0200 From: Nicolas Cannasse <ncannasse@...ion-twin.com> To: linux-kernel@...r.kernel.org Subject: poll() blocked / packets not received ? Hello, We have an application that uses pthreads and (blocking) sockets. When the application runs with one single thread in separate processes (using fork()) we don't get any problem. However when it's multithreaded, we sometimes get stuck while poll()ing a socket (with events set to POLLIN). Even after the other side of the connection has closed its side of the connection, we are still stuck here. Adding a timeout only makes the poll() exit with 0, so we loop. In case we don't loop the next operation is a recv() which will block as well (which is consistent). It seems like nothing is longer received on the socket but it's difficult to verify with tcpdump since our server outputs something like 15MB at peek time with 150 hits per seconds. We have Shorewall installed and enabled, but what seems strange is that the problem depends on multithreading. It also occurs much more often on the 4 core machines than on a 2 core ones (both with Hyperthreading activated). We're using kernel 2.6.20-15-server (#2 SMP) provided by Ubuntu. Any tip on we could fix that or investigate further would be appreciated. After one month of debugging we're really out of solution now. Best, Nicolas -- 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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