Re: Help debugging linux-next.

[Valdis . Kletnieks]

On Sun, 13 Sep 2015 14:09:21 -0300, Lucas Tanure said:

> 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.

> 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 ?

Since you obviously had a non-linux-next kernel that *did* boot, 'git bisect'
is the fastest way to find the buggy commit. The best part is that it requires
almost no actual understanding of the code.

General scheme for using git bisect, even if you have *no* idea what
the problem is:

Say you know that a 4.0 kernel works OK.  You then do:

git bisect start
get bisect bad next-201150910(or whatever the earliest known-bad is)
git bisect good v4.0 (Round stable releases like 4.0.9 to the base)

Repeat the following:

Build the kernel.  Boot it.  Reboot to a known good kernel if needed.

If it was good, use 'git bisect good'  If it died, 'git bisect bad'.
end repeat

until it tells you the bad commit. (It won't take long - going from 4.0
to current linux-next will probably take 11 to 13 times around).  And it's
simple enough to do that most of the time I have to bisect something, I'll
do it on my laptop while watching something on Netflix

*** NOTE ***
* Avoid the temptation to try to bisect between two next-2015...  tags
* because you know the problem commit is between two tags a week apart.
* Due to the way that linux-next is built, this *won't* work.  This is
* probably the single biggest cause of failure to bisect a problem in
* linux-next
*** END NOTE

Since you know the problem is i915 related, you can speed the process
up even more by doing

git bisect start -- drivers/gpu/drm/i915

which instead of considering *all* commits, will only bisect across commits
that touch that part of the source tree...


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Help debugging linux-next.

[Lucas Tanure]

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:

[ cut here ]
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
  5ca47666 88060f70b9d0 812b9159
  88060f70ba08 81074e62 880612d39000
 a06c7100 880612f66098 a06c7100 a0691760
Call Trace:
 [] dump_stack+0x4b/0x72
 [] warn_slowpath_common+0x82/0xc0
 [] warn_slowpath_null+0x1a/0x20
 [] drm_dev_alloc+0x251/0x320 [drm]
 [] drm_get_pci_dev+0x3b/0x1e0 [drm]
 [] i915_pci_probe+0x34/0x50 [i915]
 [] local_pci_probe+0x45/0xa0
 [] ? pci_match_device+0xe0/0x110
 [] pci_device_probe+0x103/0x150
 [] driver_probe_device+0x222/0x490
 [] __driver_attach+0x84/0x90
 [] ? driver_probe_device+0x490/0x490
 [] bus_for_each_dev+0x6c/0xc0
 [] driver_attach+0x1e/0x20
 [] bus_add_driver+0x1eb/0x280
 [] driver_register+0x60/0xe0
 [] __pci_register_driver+0x4c/0x50
 [] drm_pci_init+0xe0/0x110 [drm]
 [] ? 0xa06e6000
 [] i915_init+0xa4/0xab [i915]
 [] do_one_initcall+0xb3/0x200
 [] ? __vunmap+0x91/0xe0
 [] do_init_module+0x5f/0x1ef
 [] load_module+0x2197/0x27e0
 [] ? symbol_put_addr+0x50/0x50
 [] ? __pte_alloc_kernel+0xa5/0xf0
 [] SyS_init_module+0x14e/0x190
 [] entry_SYSCALL_64_fastpath+0x12/0x71
---[ end trace d2652104b24a32ff ]---
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Re: Help debugging linux-next.

[Raul Piper]

I m a newbie.is there a doc which developers follow for using
git-bisect.google misleads !!
On Sep 13, 2015 10:50 PM, "leo kirotawa"  wrote:

> git bisect would be a choice.
> Seems your issue is around i915, that is related to intel graphics,
> isolate commits in this area would be another way
>
>
>
> On Sun, Sep 13, 2015 at 2:09 PM, Lucas Tanure  wrote:
> > 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:
> >
> > [ cut here ]
> > 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
> >   5ca47666 88060f70b9d0 812b9159
> >   88060f70ba08 81074e62 880612d39000
> >  a06c7100 880612f66098 a06c7100 a0691760
> > Call Trace:
> >  [] dump_stack+0x4b/0x72
> >  [] warn_slowpath_common+0x82/0xc0
> >  [] warn_slowpath_null+0x1a/0x20
> >  [] drm_dev_alloc+0x251/0x320 [drm]
> >  [] drm_get_pci_dev+0x3b/0x1e0 [drm]
> >  [] i915_pci_probe+0x34/0x50 [i915]
> >  [] local_pci_probe+0x45/0xa0
> >  [] ? pci_match_device+0xe0/0x110
> >  [] pci_device_probe+0x103/0x150
> >  [] driver_probe_device+0x222/0x490
> >  [] __driver_attach+0x84/0x90
> >  [] ? driver_probe_device+0x490/0x490
> >  [] bus_for_each_dev+0x6c/0xc0
> >  [] driver_attach+0x1e/0x20
> >  [] bus_add_driver+0x1eb/0x280
> >  [] driver_register+0x60/0xe0
> >  [] __pci_register_driver+0x4c/0x50
> >  [] drm_pci_init+0xe0/0x110 [drm]
> >  [] ? 0xa06e6000
> >  [] i915_init+0xa4/0xab [i915]
> >  [] do_one_initcall+0xb3/0x200
> >  [] ? __vunmap+0x91/0xe0
> >  [] do_init_module+0x5f/0x1ef
> >  [] load_module+0x2197/0x27e0
> >  [] ? symbol_put_addr+0x50/0x50
> >  [] ? __pte_alloc_kernel+0xa5/0xf0
> >  [] SyS_init_module+0x14e/0x190
> >  [] entry_SYSCALL_64_fastpath+0x12/0x71
> > ---[ end trace d2652104b24a32ff ]---
> >
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>
>
>
> --
>
> --
> Leônidas S. Barbosa (Kirotawa)
> blog: corecode.wordpress.com
>
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Re: Help debugging linux-next.

[leo kirotawa]

git bisect would be a choice.
Seems your issue is around i915, that is related to intel graphics,
isolate commits in this area would be another way



On Sun, Sep 13, 2015 at 2:09 PM, Lucas Tanure  wrote:
> 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:
>
> [ cut here ]
> 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
>   5ca47666 88060f70b9d0 812b9159
>   88060f70ba08 81074e62 880612d39000
>  a06c7100 880612f66098 a06c7100 a0691760
> Call Trace:
>  [] dump_stack+0x4b/0x72
>  [] warn_slowpath_common+0x82/0xc0
>  [] warn_slowpath_null+0x1a/0x20
>  [] drm_dev_alloc+0x251/0x320 [drm]
>  [] drm_get_pci_dev+0x3b/0x1e0 [drm]
>  [] i915_pci_probe+0x34/0x50 [i915]
>  [] local_pci_probe+0x45/0xa0
>  [] ? pci_match_device+0xe0/0x110
>  [] pci_device_probe+0x103/0x150
>  [] driver_probe_device+0x222/0x490
>  [] __driver_attach+0x84/0x90
>  [] ? driver_probe_device+0x490/0x490
>  [] bus_for_each_dev+0x6c/0xc0
>  [] driver_attach+0x1e/0x20
>  [] bus_add_driver+0x1eb/0x280
>  [] driver_register+0x60/0xe0
>  [] __pci_register_driver+0x4c/0x50
>  [] drm_pci_init+0xe0/0x110 [drm]
>  [] ? 0xa06e6000
>  [] i915_init+0xa4/0xab [i915]
>  [] do_one_initcall+0xb3/0x200
>  [] ? __vunmap+0x91/0xe0
>  [] do_init_module+0x5f/0x1ef
>  [] load_module+0x2197/0x27e0
>  [] ? symbol_put_addr+0x50/0x50
>  [] ? __pte_alloc_kernel+0xa5/0xf0
>  [] SyS_init_module+0x14e/0x190
>  [] entry_SYSCALL_64_fastpath+0x12/0x71
> ---[ end trace d2652104b24a32ff ]---
>
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-- 

--
Leônidas S. Barbosa (Kirotawa)
blog: corecode.wordpress.com

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