The GPU is this one:

01:00.0 VGA compatible controller: NVIDIA Corporation G72M [Quadro NVS 110M/GeForce Go 7300] (rev a1)

The thing goes as follows:

1) I run "mplayer <random video file>", I have tried mkv and regular divx or mpeg video files, also youtube videos via the youtube-viewer tool, which uses mplayer as a backend to play youtube videos. The result is always the same, with independence of the video type.

2) The laptop seems to hang. However, I can still move the mouse. No element in the UI reacts though.

3) If I wait enough time, I am suddenly thrown out to the VT, the pc still seems quite laggy. Eventually, it recovers and I can write commands into the VT.

4) At the end of dmesg I can see by now this output:

[  268.469736] nouveau E[     DRM] GPU lockup - switching to software fbcon
[  283.487035] nouveau E[ X[2154]] failed to idle channel 0xcccc0001 [X[2154]]
[  298.487016] nouveau E[ X[2154]] failed to idle channel 0xcccc0001 [X[2154]]
[  313.487034] nouveau E[ X[2154]] failed to idle channel 0xcccc0000 [X[2154]]
[  328.487016] nouveau E[ X[2154]] failed to idle channel 0xcccc0000 [X[2154]]
[  343.587031] nouveau E[chrome[2279]] failed to idle channel 0xcccc0000 [chrome[2279]]
[  358.587019] nouveau E[chrome[2279]] failed to idle channel 0xcccc0000 [chrome[2279]]
[  373.589020] nouveau E[mplayer[2314]] failed to idle channel 0xcccc0000 [mplayer[2314]]
[  388.589031] nouveau E[mplayer[2314]] failed to idle channel 0xcccc0000 [mplayer[2314]]

5) In the X log I can see this:

(EE) [mi] EQ overflowing.  Additional events will be discarded until existing events are processed.
(EE)
(EE) Backtrace:
(EE) 0: /usr/bin/X (xorg_backtrace+0x42) [0x592d42]
(EE) 1: /usr/bin/X (mieqEnqueue+0x26b) [0x5741fb]
(EE) 2: /usr/bin/X (0x400000+0x50fc2) [0x450fc2]
(EE) 3: /usr/bin/X (xf86PostMotionEvent+0xc0) [0x489eb0]
(EE) 4: /usr/lib64/xorg/modules/input/synaptics_drv.so (0x7ff5f046c000+0x535c) [0x7ff5f047135c]
(EE) 5: /usr/lib64/xorg/modules/input/synaptics_drv.so (0x7ff5f046c000+0x6f32) [0x7ff5f0472f32]
(EE) 6: /usr/bin/X (0x400000+0x7a087) [0x47a087]
(EE) 7: /usr/bin/X (0x400000+0xa3518) [0x4a3518]
(EE) 8: /lib64/libpthread.so.0 (0x7ff5f6f47000+0x10b10) [0x7ff5f6f57b10]
(EE) 9: /lib64/libc.so.6 (ioctl+0x7) [0x7ff5f5c8e897]
(EE) 10: /usr/lib64/libdrm.so.2 (drmIoctl+0x28) [0x7ff5f6d3f258]
(EE) 11: /usr/lib64/libdrm.so.2 (drmCommandWrite+0x1b) [0x7ff5f6d4162b]
(EE) 12: /usr/lib64/libdrm_nouveau.so.2 (nouveau_bo_wait+0x89) [0x7ff5f301b959]
(EE) 13: /usr/lib64/xorg/modules/drivers/nouveau_drv.so (0x7ff5f3220000+0x7bb3) [0x7ff5f3227bb3]
(EE) 14: /usr/lib64/xorg/modules/libexa.so (0x7ff5f2bdb000+0xbba0) [0x7ff5f2be6ba0]
(EE) 15: /usr/bin/X (0x400000+0x183a73) [0x583a73]
(EE) 16: /usr/bin/X (0x400000+0xc8dc0) [0x4c8dc0]
(EE) 17: /usr/bin/X (0x400000+0x38eb8) [0x438eb8]
(EE) 18: /usr/bin/X (0x400000+0x3bd2e) [0x43bd2e]
(EE) 19: /usr/bin/X (0x400000+0x3faea) [0x43faea]
(EE) 20: /lib64/libc.so.6 (__libc_start_main+0xf5) [0x7ff5f5bcdbf5]
(EE) 21: /usr/bin/X (0x400000+0x2a541) [0x42a541]
(EE)
(EE) [mi] These backtraces from mieqEnqueue may point to a culprit higher up the stack.
(EE) [mi] mieq is *NOT* the cause.  It is a victim.

=================================

This is on Gentoo, with kernel 3.15.0 (but it also happened with 3.14.5. The arch is amd64. I am using nouveau 1.0.10, mesa 10.0.4, libdrm 2.4.52 and (probably irrelevant) mplayer 1.1.1.

The kernel is unpatched, from kernel.org (no Gentoo stuff nor anything like that).

Since I've seen several messages around the net about old kernel versions, and they eventually got fixed by a kernel update, I guess this is a good candidate for a regression. But to confirm that I will have to find an older kernel version that works. That might take some time.