Hi,

I would like some tips about how debug a issue with linux-next.

I'm trying to find things to do in kernel, and the first thing is boot the linux-next tree.

I'm able to compile the source, but when I boot I got a black screen a few times, or a just a warn in dmesg.

I'm trying to understand the issue, but no success. I tried to get kdump from the issue, but didn't work. I also tried to go back a few commits in linux-next, but my system doesn't boot at all.

How I can find the commit that create the problem, since every commit that I tested I got black screen ?

Whats the best way to debug this kind of issue ?

Thanks!

My full warning:

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WARNING: CPU: 3 PID: 243 at drivers/gpu/drm/drm_drv.c:569 drm_dev_alloc+0x251/0x320 [drm]()

Modules linked in: i915(+) joydev input_leds mousedev intel_rapl iosf_mbi x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm ttm hid_generic drm_kms_helper crct10dif_pclmul snd_hda_intel crc32_pclmul usbhid snd_hda_codec crc32c_intel drm hid ghash_clmulni_intel snd_hda_core eeepc_wmi asus_wmi aesni_intel iTCO_wdt sparse_keymap snd_hwdep led_class aes_x86_64 lrw snd_pcm iTCO_vendor_support rfkill mxm_wmi evdev gf128mul intel_gtt e1000e glue_helper mac_hid snd_timer syscopyarea ablk_helper cryptd sysfillrect psmouse snd sysimgblt pcspkr fb_sys_fops ptp mei_me i2c_i801 i2c_algo_bit soundcore mei shpchp i2c_core pps_core lpc_ich serio_raw wmi fan battery processor thermal video button sch_fq_codel ip_tables x_tables ext4 crc16 mbcache jbd2 sd_mod atkbd libps2 ahci libahci libata

xhci_pci xhci_hcd ehci_pci ehci_hcd scsi_mod usbcore usb_common i8042 serio

CPU: 3 PID: 243 Comm: systemd-udevd Not tainted 4.2.0-next-20150912-ARCH #5

Hardware name: System manufacturer System Product Name/Maximus IV GENE-Z, BIOS 3603 11/09/2012

0000000000000000 000000005ca47666 ffff88060f70b9d0 ffffffff812b9159

0000000000000000 ffff88060f70ba08 ffffffff81074e62 ffff880612d39000

ffffffffa06c7100 ffff880612f66098 ffffffffa06c7100 ffffffffa0691760

Call Trace:

[<ffffffff812b9159>] dump_stack+0x4b/0x72

[<ffffffff81074e62>] warn_slowpath_common+0x82/0xc0

[<ffffffff81074faa>] warn_slowpath_null+0x1a/0x20

[<ffffffffa0422291>] drm_dev_alloc+0x251/0x320 [drm]

[<ffffffffa0424d0b>] drm_get_pci_dev+0x3b/0x1e0 [drm]

[<ffffffffa05dd2d4>] i915_pci_probe+0x34/0x50 [i915]

[<ffffffff812fdec5>] local_pci_probe+0x45/0xa0

[<ffffffff812fde10>] ? pci_match_device+0xe0/0x110

[<ffffffff812ff053>] pci_device_probe+0x103/0x150

[<ffffffff813d7942>] driver_probe_device+0x222/0x490

[<ffffffff813d7c34>] __driver_attach+0x84/0x90

[<ffffffff813d7bb0>] ? driver_probe_device+0x490/0x490

[<ffffffff813d557c>] bus_for_each_dev+0x6c/0xc0

[<ffffffff813d70fe>] driver_attach+0x1e/0x20

[<ffffffff813d6c4b>] bus_add_driver+0x1eb/0x280

[<ffffffff813d8540>] driver_register+0x60/0xe0

[<ffffffff812fd73c>] __pci_register_driver+0x4c/0x50

[<ffffffffa0424f90>] drm_pci_init+0xe0/0x110 [drm]

[<ffffffffa06e6000>] ? 0xffffffffa06e6000

[<ffffffffa06e60a4>] i915_init+0xa4/0xab [i915]

[<ffffffff81002123>] do_one_initcall+0xb3/0x200

[<ffffffff81199801>] ? __vunmap+0x91/0xe0

[<ffffffff811589a0>] do_init_module+0x5f/0x1ef

[<ffffffff810fa707>] load_module+0x2197/0x27e0

[<ffffffff810f7550>] ? symbol_put_addr+0x50/0x50

[<ffffffff81188695>] ? __pte_alloc_kernel+0xa5/0xf0

[<ffffffff810fae9e>] SyS_init_module+0x14e/0x190

[<ffffffff8157046e>] entry_SYSCALL_64_fastpath+0x12/0x71

---[ end trace d2652104b24a32ff ]---