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I am running on Ubuntu 10.04 LTS Server an GTK application that used to work fine. It suddenly started to hang in interruptible state (Sl+) without any apparent reason. Here is a snippet of the strace:

poll([{fd=3, events=POLLIN}, {fd=5, events=POLLIN}], 2, 0) = 0 (Timeout)
poll([{fd=5, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=5, revents=POLLOUT}])
writev(5, [{"\2\30\4\0\224\4\240\0\0@\0\0\37\0\240\0\2\4\4\0\224\4\240\0\0@\0\0\37\0\240\0"..., 192}, {NULL, 0}, {"", 0}], 3) = 192
read(5, 0x2ba9ac4, 4096)                = -1 EAGAIN (Resource temporarily unavailable)

I googled that line read(5, 0x2ba9ac4, 4096), which seems to be more significant, and it seems that many other applications tend to have the same problem. I tried to restart my X server, but it didn't help.

Do you have an idea how to solve this problem?

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what is the application? – RolandiXor Mar 4 '11 at 19:03
webots, by, probably not really helpful, but anyway. – Greg Mar 5 '11 at 17:04
up vote 4 down vote accepted

It's attempting to read a socket and is hanging waiting for the server to respond. You might not have a timeout for the socket or your internet may be not fully functional, or the target server might be causing you to wait without response.

Either way, this is an issue for the developers of the program to sort out, they need to make sure all their reads have timeouts and errors and perhaps retrying. Unless the developers have looked at the issue and determined it's a upstream library issue or a downstream packaging issue.

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