Googling I've found that this is somewhat old bug which never was addressed. I upgraded glibc and now I can see following in system log: Apr 13 17:30:01 localhost cron[18826]: PAM unable to dlopen(/lib64/security/pam_unix.so): /lib64/libpthread.so.0: symbol __h_errno, version GLIBC_PRIVATE not defined in file libc.so.6 with link time reference Unfortunately, revdep-rebuild did not catch this problem. Reproducible: Always See referenced URL to read about this issue discussed back in Nov 2011.
Created attachment 430328 [details] emerge --info (too big to paste)
Apparently, the only thing that had to be done was to restart the cron daemon. Without it these pam-related syslog messages won't stop. I guess restarting of cron daemon should be one of glibc post-install steps. I think this one can be closed.
