Starting with 2.6.40-4, the kernel boots without any issue, but after a couple of minutes completely freezes. Without any traces in system logs, simply complete freeze, the only way out is switching off. It happens usually during an X11 session, where the system suddenly stops responding, mouse and keypad do not respond and the screen image simply freezes.
The hardware in use is AMD Semtron 3000+ in Fuji-Siemens Taleo, with Radeon HD3450 (but I am not using any specific driver from Radeon, just the Fedora default graphics driver).
This behaviour does not occur under 2.6.18-4 or earlier, I have observed it only on 2.6.40-4 and 18.104.22.168-0.
Sorry for the typo, the last paragraph should state "under 2.6.38-4 or earlier".
can you try running the kernel-debug package for a while, and see if you get any traces, or similar appearing ?
Created attachment 522942 [details]
syslogd output for, among others, kern.*
Somehow my last comment got lost.
Running with kernel-debug (22.214.171.124-5) and after some tricking, redirecting syslog kern.* to /var/log/messages results in the attached file. It indeed shows a kernel deadlock condition in the end.
The lockdep report you attached was supposedly fixed by upstream commit 8c0bec2151a47906bf779c6715a10ce04453ab77. That was contained in the 3.1 kernel, which is now in F15 as 2.6.41.x.
If you are still seeing this issue, please reopen this bug and let us know which 2.6.41.x kernel version you see it with and try to get a backtrace as before.