I'm using ubuntu 15.04 on a thinkpad s440 laptop.

This laptop uses a Intel Haswel card and a AMD HD8670M and i'm the distro default mesa driver (10.5.2)

i' doing this to enable DRI_PRIME support:

xrandr --setprovideroffloadsink radeon Intel
xcompmgr &
DRI_PRIME=1 steam

please note that i'm using fluxbox and if i don't enble xcompmgr i don't seen anthing (DRI_PRIME=1 glxgears will only show up a "empty" windows, where with xcompmgr i can see the glxgears running)

So first problem is this, i require xcompmgr to enable DRI_PRIME. Also check this bug report: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1430888

If not dupe, i can open a new bug for this problem.

Anyway main problem...

A few seconds after starting steam i get a crash, with this dump:

May  7 00:46:12 danielleite kernel: [  230.148387] [drm] ib test on ring 1 succeeded in 0 usecs
May  7 00:46:12 danielleite kernel: [  230.148409] [drm] ib test on ring 2 succeeded in 0 usecs
May  7 00:46:12 danielleite kernel: [  230.148424] [drm] ib test on ring 3 succeeded in 0 usecs
May  7 00:46:12 danielleite kernel: [  230.148442] [drm] ib test on ring 4 succeeded in 0 usecs
May  7 00:46:20 danielleite kernel: [  238.246752] BUG: unable to handle kernel NULL pointer dereference at 0000000000000d60
May  7 00:46:20 danielleite kernel: [  238.246777] IP: [<ffffffffc046d049>] radeon_fence_signaled+0x49/0x90 [radeon]
May  7 00:46:20 danielleite kernel: [  238.246810] PGD 222766067 PUD 0 
May  7 00:46:20 danielleite kernel: [  238.246820] Oops: 0000 [#1] SMP 
May  7 00:46:20 danielleite kernel: [  238.246830] Modules linked in: xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter ip_tables x_tables pci_stub vboxpci(OE) vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) ctr ccm binfmt_misc rfcomm bnep arc4 uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_core v4l2_common intel_rapl iosf_mbi btusb x86_pkg_temp_thermal videodev bluetooth intel_powerclamp media iwlmvm coretemp mac80211 kvm_intel kvm snd_hda_codec_hdmi snd_hda_codec_conexant snd_hda_codec_generic iwlwifi joydev snd_hda_intel serio_raw snd_hda_controller snd_hda_codec snd_hwdep thinkpad_acpi nvram cfg80211 rtsx_pci_ms lpc_ich snd_seq_midi snd_pcm snd_seq_midi_event snd_rawmidi memstick mei_me mei shpchp snd_seq snd_seq_device snd_timer snd soundcore intel_smartconnect mac_hid parport_pc ppdev lp parport autofs4 btrfs xor raid6_pq dm_crypt rtsx_pci_sdmmc crct10dif_pclmul crc32_pclmul amdkfd amd_iommu_v2 ghash_clmulni_intel radeon aesni_intel aes_x86_64 lrw gf128mul glue_helper i915 ablk_helper cryptd psmouse ttm i2c_algo_bit drm_kms_helper ahci libahci drm r8169 rtsx_pci mii video
May  7 00:46:20 danielleite kernel: [  238.247160] CPU: 0 PID: 3323 Comm: steam Tainted: G           OE   4.0.0-040000-generic #201504121935
May  7 00:46:20 danielleite kernel: [  238.247182] Hardware name: LENOVO 20AYA05KPG/20AYA05KPG, BIOS J3ET59WW (1.59 ) 07/15/2014
May  7 00:46:20 danielleite kernel: [  238.247203] task: ffff8802249c5a00 ti: ffff8800bb0a0000 task.ti: ffff8800bb0a0000
May  7 00:46:20 danielleite kernel: [  238.247221] RIP: 0010:[<ffffffffc046d049>]  [<ffffffffc046d049>] radeon_fence_signaled+0x49/0x90 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247253] RSP: 0018:ffff8800bb0a3978  EFLAGS: 00010246
May  7 00:46:20 danielleite kernel: [  238.247266] RAX: 0000000000000000 RBX: ffff8800c6d0f480 RCX: 000000010040001c
May  7 00:46:20 danielleite kernel: [  238.247283] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
May  7 00:46:20 danielleite kernel: [  238.247301] RBP: ffff8800bb0a3998 R08: ffff8802235fc8c0 R09: 000000010040001c
May  7 00:46:20 danielleite kernel: [  238.247318] R10: ffffffffc04e032c R11: 0000000000018bf8 R12: 0000000000000000
May  7 00:46:20 danielleite kernel: [  238.247335] R13: 0000000000000d60 R14: 0000000000000100 R15: ffff8802249c5a00
May  7 00:46:20 danielleite kernel: [  238.247353] FS:  0000000000000000(0000) GS:ffff88022f200000(0063) knlGS:00000000f39b2b40
May  7 00:46:20 danielleite kernel: [  238.247372] CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
May  7 00:46:20 danielleite kernel: [  238.247386] CR2: 0000000000000d60 CR3: 0000000223512000 CR4: 00000000001407f0
May  7 00:46:20 danielleite kernel: [  238.247411] Stack:
May  7 00:46:20 danielleite kernel: [  238.247421]  ffff8800bb0a3998 ffff880224a83c40 ffff88020c3e56c0 ffff880221305a38
May  7 00:46:20 danielleite kernel: [  238.247443]  ffff8800bb0a39c8 ffffffffc04e03b4 ffff8800bb0a3c00 ffff880221305990
May  7 00:46:20 danielleite kernel: [  238.247463]  ffff8800bb0a3c00 0000000000005d00 ffff8800bb0a3ac8 ffffffffc04e0ac8
May  7 00:46:20 danielleite kernel: [  238.247483] Call Trace:
May  7 00:46:20 danielleite kernel: [  238.247508]  [<ffffffffc04e03b4>] radeon_sa_bo_try_free+0x64/0x80 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247540]  [<ffffffffc04e0ac8>] radeon_sa_bo_new+0xf8/0x3b0 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247567]  [<ffffffffc0489050>] ? radeon_irq_kms_disable_hpd+0xb0/0xb0 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247599]  [<ffffffffc053bfb2>] radeon_ib_get+0x42/0xe0 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247625]  [<ffffffffc04891e5>] radeon_cs_ib_fill+0x85/0x220 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247652]  [<ffffffffc048a35b>] radeon_cs_ioctl+0x10b/0x200 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247677]  [<ffffffffc0135ee6>] drm_ioctl+0x2e6/0x590 [drm]
May  7 00:46:20 danielleite kernel: [  238.247702]  [<ffffffffc048a250>] ? radeon_cs_parser_init+0x400/0x400 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247722]  [<ffffffff810f8372>] ? futex_wake+0x72/0x140
May  7 00:46:20 danielleite kernel: [  238.247742]  [<ffffffffc045134d>] radeon_drm_ioctl+0x5d/0xa0 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247769]  [<ffffffffc054c9a4>] radeon_kms_compat_ioctl+0x14/0x30 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247788]  [<ffffffff81250308>] compat_SyS_ioctl+0xb8/0x220
May  7 00:46:20 danielleite kernel: [  238.247804]  [<ffffffff817f25ea>] sysenter_dispatch+0x7/0x21
May  7 00:46:20 danielleite kernel: [  238.247817] Code: 89 fb 4c 89 6d f8 74 39 8b 77 68 4c 8b 67 60 48 8b 7f 58 89 f0 48 89 c2 48 c1 e0 08 48 c1 e2 04 48 29 d0 4c 8d ac 07 60 0d 00 00 <49> 8b 45 00 49 39 c4 77 1e 48 89 df e8 96 e0 0e c1 b8 01 00 00 
May  7 00:46:20 danielleite kernel: [  238.247893] RIP  [<ffffffffc046d049>] radeon_fence_signaled+0x49/0x90 [radeon]
May  7 00:46:20 danielleite kernel: [  238.247919]  RSP <ffff8800bb0a3978>
May  7 00:46:20 danielleite kernel: [  238.247927] CR2: 0000000000000d60
May  7 00:46:20 danielleite kernel: [  238.252481] ---[ end trace b0a26b210316c3d3 ]---

Thanks for the help and for mesa & open drivers!