Red Hat Bugzilla – Bug 1014550
X server hangs forever fetching NIS passwd entry for siLocalCredCheckAddr
Last modified: 2015-02-17 12:27:54 EST
Created attachment 806373 [details]
gdb traceback of the hanging X server
I'm not sure if this is an X server bug or a glibc bug, and it's something that happens randomly and rarely so unfortunately there is not much debugging info available. I would appreciate tips on how to collect useful info, while at the same time hoping I don't hit this bug again because it's incredibly annoying when it does hit. I had been running Fedora 19 for only about five hours when the hang happened. We also have a couple of users who occasionally get this hang on Fedora 17, though my previous F17 machine was never affected.
The problem manifests itself when the X server suddenly stops dead; no further interaction is possible and no further display updates occur. Attaching strace to the running server just produces an infinite loop of "poll ... SIGALRM ... poll ...", while attaching gdb shows that it is stuck deep inside getpwnam() while processing a siLocalCredCheckAddr for the xhost entry "SI:localuser:xxx" (where xxx is the logged-in user).
The machines in question all get their passwd info from NIS (the nsswitch entry says "passwd: compat") and although the NIS subsystem works 99% of the time, we do occasionally get "do_ypcall: clnt_call: RPC: Timed out" errors logged, for reasons we can't fathom. It's my speculation that the X server hang coincides with one of these (although there is no syslog entry to that effect).
I am guessing that this would be mitigated by using the user's decimal uid in the xhost entry instead of their login name. I'm not sure what process adds this, but it might be worth making that the default.
xorg.conf is not attached because at least one of the machines where this happens has no xorg.conf. Xorg.0.log is not attached because the log was overwritten when the machine was rebooted (but probably didn't say anything useful). A gdb traceback at the hanging point is attached.
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