dnf-0.6.4-5.fc21.noarch Attempting to do a manual "dnf update" gave the following message then stalled: Waiting for process with pid 20324 to finish. That process was the periodic makecache: PID TTY STAT TIME COMMAND 20324 ? SNs 0:25 /usr/bin/python -OO /usr/bin/dnf -v makecache timer stracing it: Process 20324 attached select(41, [38 39 40], [], [], {0, 32573}) = 0 (Timeout) poll([{fd=38, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 0) = 0 (Timeout) poll([{fd=39, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 0) = 0 (Timeout) poll([{fd=40, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 0) = 0 (Timeout) select(41, [38 39 40], [], [], {1, 0}) = 0 (Timeout) poll([{fd=38, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 0) = 0 (Timeout) poll([{fd=39, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 0) = 0 (Timeout) poll([{fd=40, events=POLLIN|POLLPRI|POLLRDNORM|POLLRDBAND}], 1, 0) = 0 (Timeout) select(41, [38 39 40], [], [], {1, 0}) = 0 (Timeout) [...] Those fds are: lrwx------ 1 root root 64 Aug 15 03:33 40 -> socket:[12259455] lrwx------ 1 root root 64 Aug 15 03:33 39 -> socket:[12259454] lrwx------ 1 root root 64 Aug 15 03:33 38 -> socket:[12259453] tcp6 0 0 <...>:44827 2001:67c:1220:e100::93e5:390:80 ESTABLISHED 0 12259455 20324/python tcp6 0 0 <...>:44825 2001:67c:1220:e100::93e5:390:80 ESTABLISHED 0 12259453 20324/python tcp6 0 0 <...>:44826 2001:67c:1220:e100::93e5:390:80 ESTABLISHED 0 12259454 20324/python The remote host resolves to mirror.cis.vutbr.cz. This was at 2015-08-17 18:10, so it looks like it's been in that state for over 2.5 days. Given that it's reading from port 80 I guess it's send a HTTP request and is waiting for a response. Either the remote server is just sitting there doing nothing, or due to some network glitch the remote end has gone away but we never received a FIN or RST. When that happens, because in the absence of SO_KEEPALIVE a TCP receiver doesn't *require* any packets to be received, unlike a TCP sender which must receive a timely ACK or it will abort the connection, a receiver that missed the FIN/RST can hang indefinitely unless it implements some sort of timeout of its own. (Or enables SO_KEEPALIVE on the socket, though the default timeout on that is still a little over 2 hours, which is a bit high for this kind of thing.) I recovered this with "systemctl stop dnf-makecache.service", but I'd expect some reasonable kind of timeout to deal with duff mirrors and network glitches alike. (Err, just noticed as well: why poll() all the fds individually if select() on them didn't return? The answer's really not likely to have changed...)
This issue has been fixed in F22 version of dnf. Would you like to request a backport?
Dunno. This machine may be on F21 for a while yet, so notionally yet. OTOH I've effectively bypassed the cache by setting metadata_expire=1 so it updates when I ask it. I may disable the dnf-makecache.service completely as well to avoid pointless background updates. Even with it running, now I know what to look for I know how to recover (though it hasn't happened to me again yet, but other people on F21 may appreciate not bumping into this at all.) My bigger issue atm is bug 1252106.
s/notionally yet/notionally yes/
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