Subject: Re: X and date change causes hang
To: Martin Husemann <firstname.lastname@example.org>
From: Steven M. Bellovin <email@example.com>
Date: 11/22/2004 07:59:52
In message <20041122102202.GD6225@drowsy.duskware.de>, Martin Husemann writes:
>On Sun, Nov 21, 2004 at 07:45:45PM -0500, David H. Gutteridge wrote:
>> Moving date forward six months: 26 second freeze
>> Moving date forward one year: 84 second freeze
>> Moving date forward two years: 175 second freeze
>Wow, I couldn't believe this - but I can reproduce it on -current.
>Please file a PR in the bin category against date(1) - and in the xsrc
>category against X (this is probably a X server bug, since during the freeze
>all X output stalls).
I wonder if this is really a bug at all. Does cron try to catch up?
An X server is just an application (unlike, say, ping replies or
console output without X); if it's competing for CPU with other,
high-priority processes, it's not a surprise that it would freeze.
There may be some component to X itself -- if it's in a select() loop
trying to make something move smoothly, it may be running through a lot
of steps catching up to the current time, even if no draw events are
pending. But let's try to understand whether or not the CPU is 110%
busy. What is the accumulated CPU time of X before and after the change?
What about other processes? Does lastcomm show anything?
--Steve Bellovin, http://www.research.att.com/~smb