Dovecot (v1.1.rc8) died tonight, with an error about time moving backwards by 4398 seconds. I can see from logs that this has happend a few times before with the imap processes, without me noticing. I sure noticed the master process missing, though :-).
I was puzzled that it was always 4398 seconds, in particular because this server runs an NTP daemon. A little searching for this problem shows that it is an issue with the Linux kernel gettimeofday(), see e.g. http://lkml.org/lkml/2007/8/23/96 Below is a patch (untested) to work around this issue. Do you see something wrong with this approach, apart from the uglyness? I just picked the 4395-4400 values by chance. Can you figure out how big the window should be? Thanks, Anders. --- ./src/lib/ioloop.c-orig 2008-06-20 10:45:54.000000000 +0200 +++ ./src/lib/ioloop.c 2008-06-20 10:47:36.000000000 +0200 @@ -230,8 +230,13 @@ struct timeval tv, tv_call; unsigned int t_id; - if (gettimeofday(&ioloop_timeval, &ioloop_timezone) < 0) - i_fatal("gettimeofday(): %m"); + /* The Linux gettimeofday() will sometimes jump forward + * by approximately 4398 seconds. Ignore that reading. */ + do { + if (gettimeofday(&ioloop_timeval, &ioloop_timezone) < 0) + i_fatal("gettimeofday(): %m"); + } while (4395 < (ioloop_timeval.tv_sec - ioloop_time) + && (ioloop_timeval.tv_sec - ioloop_time) < 4400); /* Don't bother comparing usecs. */ if (ioloop_time > ioloop_timeval.tv_sec) {
