I've upgraded to 15.04 and now I'm hitting the very same bug.
Compiz will use 100% CPU and the UI freezes, the offending compiz instance will persist consuming CPU time even after systemctl restart lightdm and can only be killed by SIGKILL.
I'm also seeing
[17409.810980] NVRM: GPU at PCI:0000:01:00: GPU-50e94984-5501-8f36-bc04-b29c484a5f1e
[17409.810988] NVRM: Xid (PCI:0000:01:00): 13, Graphics Exception: ChID 0003, Class 00008397, Offset 00000e08, Data 04b00000
[17410.915719] NVRM: Xid (PCI:0000:01:00): 13, Graphics Exception: ChID 0003, Class 00008397, Offset 00000f10, Data 44960000
[17421.432239] NVRM: Xid (PCI:0000:01:00): 13, Graphics Exception: ChID 0003, Class 00008397, Offset 00000f10, Data 44960000
[17431.525701] NVRM: Xid (PCI:0000:01:00): 13, Graphics Exception: ChID 0003, Class 00008397, Offset 00000f10, Data 44960000
I've upgraded to 15.04 and now I'm hitting the very same bug.
Compiz will use 100% CPU and the UI freezes, the offending compiz instance will persist consuming CPU time even after systemctl restart lightdm and can only be killed by SIGKILL.
I'm also seeing
[17409.810980] NVRM: GPU at PCI:0000:01:00: GPU-50e94984- 5501-8f36- bc04-b29c484a5f 1e
[17409.810988] NVRM: Xid (PCI:0000:01:00): 13, Graphics Exception: ChID 0003, Class 00008397, Offset 00000e08, Data 04b00000
[17410.915719] NVRM: Xid (PCI:0000:01:00): 13, Graphics Exception: ChID 0003, Class 00008397, Offset 00000f10, Data 44960000
[17421.432239] NVRM: Xid (PCI:0000:01:00): 13, Graphics Exception: ChID 0003, Class 00008397, Offset 00000f10, Data 44960000
[17431.525701] NVRM: Xid (PCI:0000:01:00): 13, Graphics Exception: ChID 0003, Class 00008397, Offset 00000f10, Data 44960000
in dmesg
OpenGL renderer string: GeForce GTX 260/PCIe/SSE2
NVIDIA Driver Version: 340.76
Linux rechenknecht2k7 3.19.0-15-generic #15-Ubuntu SMP Thu Apr 16 23:32:37 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
Tell me if this is a different bug and I should open a new issue.