I have the same problem.  This happens without fail after some period of inactivity.  Here's my stack:


[25559.979128] [fglrx] ASIC hang happened
[25559.979146] Pid: 1263, comm: Xorg Tainted: P            3.0.0-13-generic #22-Ubuntu
[25559.979152] Call Trace:
[25559.979279]  [<ffffffffa01a2d7e>] KCL_DEBUG_OsDump+0xe/0x10 [fglrx]
[25559.979340]  [<ffffffffa01b020c>] firegl_hardwareHangRecovery+0x1c/0x50 [fglrx]
[25559.979438]  [<ffffffffa0233544>] ? _ZN18mmEnginesContainer9timestampEP26_QS_MM_TIMESTAMP_PACKET_INP27_QS_MM_TIMESTAMP_PACKET_OUT+0x184/0x1c0 [fglrx]
[25559.979452]  [<ffffffff81012bee>] ? __switch_to_xtra+0x14e/0x180
[25559.979515]  [<ffffffffa01cc422>] ? firegl_trace+0x72/0x1e0 [fglrx]
[25559.979610]  [<ffffffffa023e8b3>] ? _ZN8mmEngine9timestampEv+0x63/0x90 [fglrx]
[25559.979701]  [<ffffffffa02334a2>] ? _ZN18mmEnginesContainer9timestampEP26_QS_MM_TIMESTAMP_PACKET_INP27_QS_MM_TIMESTAMP_PACKET_OUT+0xe2/0x1c0 [fglrx]
[25559.979767]  [<ffffffffa01cedf0>] ? firegl_cmmqs_notify_mvpu+0x2e0/0x2e0 [fglrx]
[25559.979850]  [<ffffffffa021403a>] ? IsThreadTSExpired+0xca/0x110 [fglrx]
[25559.979914]  [<ffffffffa01cee4b>] ? firegl_cmmqs_TSExpired+0x5b/0xd0 [fglrx]
[25559.979969]  [<ffffffffa01a3945>] ? KCL_WAIT_Add_Exclusive+0x65/0x80 [fglrx]
[25559.980030]  [<ffffffffa01babfa>] ? irqmgr_wrap_wait_for_hifreq_interrupt_ex+0xba/0x3d0 [fglrx]
[25559.980112]  [<ffffffffa01b8f7b>] ? MCIL_SuspendThread+0xdb/0x120 [fglrx]
[25559.980208]  [<ffffffffa021d862>] ? _ZN2OS13suspendThreadEj+0x22/0x30 [fglrx]
[25559.980296]  [<ffffffffa021655f>] ? CMMQSWaitOnTsSignal+0xaf/0xd0 [fglrx]
[25559.980389]  [<ffffffffa0225c72>] ? _Z8uCWDDEQCmjjPvjS_+0xc32/0x10c0 [fglrx]
[25559.980460]  [<ffffffffa01ce932>] ? firegl_cmmqs_CWDDE_32+0x332/0x440 [fglrx]
[25559.980529]  [<ffffffffa01cd260>] ? firegl_cmmqs_CWDDE32+0x70/0x100 [fglrx]
[25559.980547]  [<ffffffff812831ca>] ? security_capable+0x2a/0x30
[25559.980614]  [<ffffffffa01cd1f0>] ? firegl_cmmqs_createdriver+0x170/0x170 [fglrx]
[25559.980677]  [<ffffffffa01abe18>] ? firegl_ioctl+0x1e8/0x250 [fglrx]
[25559.980735]  [<ffffffffa019c9be>] ? ip_firegl_unlocked_ioctl+0xe/0x20 [fglrx]
[25559.980750]  [<ffffffff8117959a>] ? do_vfs_ioctl+0x8a/0x340
[25559.980763]  [<ffffffff811798e1>] ? sys_ioctl+0x91/0xa0
[25559.980779]  [<ffffffff815f27c2>] ? system_call_fastpath+0x16/0x1b
[25559.980795] pubdev:0xffffffffa03ff600, num of device:1 , name:fglrx, major 8, minor 88. 
[25559.980808] device 0 : 0xffff880230c94000 .
[25559.980818] Asic ID:0x9802, revision:0x23, MMIOReg:0xffffc90012e00000.
[25559.980830] FB phys addr: 0xc0000000, MC :0xf00000000, Total FB size :0x18000000.
[25559.980843] gart table MC:0xf0fbfd000, Physical:0xcfbfd000, size:0x402000.
[25559.980856] mc_node :FB, total 1 zones
[25559.980866]     MC start:0xf00000000, Physical:0xc0000000, size:0x10000000.
[25559.980879]     Mapped heap -- Offset:0x0, size:0xfbfd000, reference count:69, mapping count:0,
[25559.980892]     Mapped heap -- Offset:0x0, size:0x1000000, reference count:1, mapping count:0,
[25559.980907]     Mapped heap -- Offset:0xfbfd000, size:0x403000, reference count:1, mapping count:0,
[25559.980920] mc_node :INV_FB, total 1 zones
[25559.980930]     MC start:0xf10000000, Physical:0xd0000000, size:0x8000000.
[25559.980942]     Mapped heap -- Offset:0x7ff4000, size:0xc000, reference count:1, mapping count:0,
[25559.980955] mc_node :GART_USWC, total 2 zones
[25559.980964]     MC start:0x40100000, Physical:0x0, size:0x50000000.
[25559.980976]     Mapped heap -- Offset:0x0, size:0x2000000, reference count:11, mapping count:0,
[25559.980989] mc_node :GART_CACHEABLE, total 3 zones
[25559.980999]     MC start:0x10400000, Physical:0x0, size:0x2fd00000.
[25559.981011]     Mapped heap -- Offset:0x4900000, size:0x900000, reference count:2, mapping count:0,
[25559.981025]     Mapped heap -- Offset:0x4000000, size:0x900000, reference count:2, mapping count:0,
[25559.981039]     Mapped heap -- Offset:0x3700000, size:0x900000, reference count:2, mapping count:0,
[25559.981053]     Mapped heap -- Offset:0x2e00000, size:0x900000, reference count:2, mapping count:0,
[25559.981068]     Mapped heap -- Offset:0x2500000, size:0x900000, reference count:2, mapping count:0,
[25559.981082]     Mapped heap -- Offset:0x1400000, size:0x900000, reference count:15, mapping count:0,
[25559.981096]     Mapped heap -- Offset:0xb00000, size:0x900000, reference count:9, mapping count:0,
[25559.981112]     Mapped heap -- Offset:0x200000, size:0x900000, reference count:16, mapping count:0,
[25559.981126]     Mapped heap -- Offset:0x0, size:0x200000, reference count:18, mapping count:0,
[25559.981140]     Mapped heap -- Offset:0xef000, size:0x11000, reference count:1, mapping count:0,
[25559.981155] GRBM : 0xe7734828, SRBM : 0x20004840 .
[25559.981167] CP_RB_BASE : 0x401000, CP_RB_RPTR : 0x33750 , CP_RB_WPTR :0x338b0.
[25559.981180] CP_IB1_BUFSZ:0xcf8, CP_IB1_BASE_HI:0x0, CP_IB1_BASE_LO:0x40725000.
[25559.981193] last submit IB buffer -- MC :0x40725000,phys:0x222506000.
[25559.981209] Dump the trace queue.
[25559.981216] End of dump