I have a PC running RHEL6.5, and had a new problem emerge yesterday after installing a new video card (Radeon HD5450, PCIe1x) and configuring it to use three monitors (connected via DisplayPort, DVI, and VGA). Previously, it was using the motherboard video with a single monitor.
Once or twice per hour, the system appears to freeze. Sometimes the mouse pointer disappears, sometimes it simply becomes immobile.
Keyboard input appears to be buffered during the freeze & executed once the freeze ends 5-10 seconds later. In other words, if I do something like ctrl+tab while it's frozen, it has no immediate effect, but once the computer comes back to life a few seconds later, it launches the Gnome task launcher.
I'm not sure about mouse input... I've never had the pointer freeze over something potentially-clickable to see whether the click was buffered.
I've never managed to observe it happening when there was sound playing in the background, so I don't know whether the freezes begin and end with desktop-rendering, or involve some deeper scheduling problem.
There seems to be some correlation with rendering activity, like navigating to a new URL in Firefox & having the system freeze a moment after it renders the initial view of the page.
If it's a hardware problem, then it's probably something endemic to the design or implementation itself, and not a random build-quality defect. I have 4 coworkers with identical hardware who've all reported the same problem.
I know that under Windows (Vista, in particular), this problem is usually caused by over-aggressive IRQ-sharing.
Update The hangs seem to be 3-4 seconds, and there are entries in /var/log/Xorg.0.log like the following whose timestamps appear to correlate with the beginning of the freeze:
[ 4782.094] AUDIT: Tue Jun 10 16:24:53 2014: 4963: client 37 connected from local host ( uid=999 gid=999 pid=5339 ) Auth name: MIT-MAGIC-COOKIE-1 ID: 741 [ 4782.094] AUDIT: Tue Jun 10 16:24:53 2014: 4963: client 37 disconnected
If I press and release the Ctrl key during a freeze (I enabled "locate mouse" to help recognize freezes), it has no effect at the moment I press it... but the blue aura appears the moment everything else unfreezes 2-3 seconds later.
I looked up the pids of the last few entries in the log... Most were Nautilus, a few were Brasero (CD/DVD burning). The optical drive has no disc. Perhaps the second or two hang is being caused by something trying to autoprobe for a nonexistent optical disc that hangs everything else until it times out?
(side question: is it even possible for a badly-behaving app to swallow & hold on to the mouse pointer or hang the UI? Or, in theory at least, is the window manager supposed to be completely indifferent to the state of the running apps and the rest of the OS?)
UPDATE 2 Looking at the timestamps in Xorg.0.log, the hangs are happening almost like clockwork every 2:49... 4:41:47, 4:44:36, 4:47:25, 4:50:14, etc.