Re: [PATCHv3 00/13] scripts/gdb: Linux awareness debug commands

[Kieran Bingham]

On 13/03/16 16:35, Jan Kiszka wrote:
> On 2016-03-03 12:40, Kieran Bingham wrote:
>> Hi Jan,
>>
>> V3 of the patchset respun. Now finally adding the lx-interrupts command
>> after I resolved my issues with the Radix Tree parsing.
>>
>> This command only provides the interrupts that are available generically,
>> and it seems that the /proc/interrupts function calls into arch specific
>> layers to add extra information about arch specific interrupts.
>>
>> I'm not sure what to do about this yet - The values returned appear to be
>> accurate - but it's just a subset of the information returned by proc.
>>
> 
> I didn't test this (due to the breakage in patch 10): Can you give
> examples of what is missing, e.g. on ARM or x86?
On ARM this is :

(gdb) lx-interrupts
            CPU0       CPU1
  18:     587828     150187
  36:      66574          0
  41:          8          0
  42:        106          0
  43:        100          0
(gdb) c


vs

root@ArmACookieMonster:~# cat /proc/interrupts
           CPU0       CPU1
 18:     588057     150274     GIC-0  27 Edge      arch_timer
 20:          0          0     GIC-0  34 Level     timer
 36:      66599          0     GIC-0  47 Level     eth0
 39:          0          0     GIC-0  41 Level     mmci-pl18x (cmd)
 40:          0          0     GIC-0  42 Level     mmci-pl18x (pio)
 41:          8          0     GIC-0  44 Level     kmi-pl050
 42:        106          0     GIC-0  45 Level     kmi-pl050
 43:        112          0     GIC-0  37 Level     uart-pl011
 49:          0          0     GIC-0  36 Level     rtc-pl031
IPI0:          0          1  CPU wakeup interrupts
IPI1:          0          0  Timer broadcast interrupts
IPI2:      15867     281362  Rescheduling interrupts
IPI3:          0          6  Function call interrupts
IPI4:          0          0  CPU stop interrupts
IPI5:          0          0  IRQ work interrupts
IPI6:          0          0  completion interrupts
Err:          0

So quite a substantial subset :(

> 
>> lx_thread_info_by_pid has been useful to me while looking at thread
>> awareness, so I've included it into this patch set now. It makes finding
>> internal thread information much more convenient.
>>
>> dentry_name has been moved to the utils module, as I am already using it
>> in another command, so it's just not appropriate to be in proc.py
>>
>> The cpu_list mask iterators make calling for cpu in each_online_cpu() read
>> nicely, and I've left the print_cpus() function in for now as a hidden
>> helper. It can be used by calling:
>>   python linux.cpus.print_cpus()
>> to check these generators, which I thought was quite nice - but I didn't
>> know if it warranted a full command class for this.
>>
>> For convenience, this patch set submission can be found at
>>   http://git.linaro.org/people/kieran.bingham/linux.git gdb-scripts-2016-03-03-lkml-submission
>>
>> Patchset Changelog:
>> v3:
>>  - Radix Tree parser introduced
>>  - cpu_list mask iterators added
>>  - lx-interrupts command implemented
>>  - dentry_name function moved to utils
>>  - lx-meminfo command PEP8 warnings fixed
>>  - lx_thread_info_by_pid introduced
>>
>> v2:
>>  - Reworked iterators with improved versions from Jeff Mahoney
>>  - Fixed !CONFIG_MODULES and !CONFIG_MMU support
>>  - Improvements on lx-meminfo
>>  - constants.py generated by Kbuild
>>  - IS_BUILTIN facility used to provide LX_CONFIG values
>>
>> v1:
>>  - Introduced lx-iomem, lx-ioports, lx-mounts, lx-meminfo
>>
>> Kieran Bingham (13):
>>   scripts/gdb: Provide linux constants
>>   scripts/gdb: Provide kernel list item generators
>>   scripts/gdb: Convert modules usage to lists functions
>>   scripts/gdb: Provide exception catching parser
>>   scripts/gdb: Support !CONFIG_MODULES gracefully
>>   scripts/gdb: Provide a dentry_name VFS path helper
>>   scripts/gdb: Add io resource readers
>>   scripts/gdb: Add mount point list command
>>   scripts/gdb: Add meminfo command
>>   scripts/gdb: Add cpu iterators
>>   scripts/gdb: Add a Radix Tree Parser
>>   scripts/gdb: Add interrupts command
>>   scripts/gdb: Add lx_thread_info_by_pid helper
>>
>>  Kbuild                            |  10 +
>>  scripts/gdb/linux/Makefile        |  12 +-
>>  scripts/gdb/linux/constants.py.in |  93 ++++++++
>>  scripts/gdb/linux/cpus.py         |  21 ++
>>  scripts/gdb/linux/lists.py        |  20 ++
>>  scripts/gdb/linux/modules.py      |  22 +-
>>  scripts/gdb/linux/proc.py         | 449 ++++++++++++++++++++++++++++++++++++++
>>  scripts/gdb/linux/radixtree.py    |  74 +++++++
>>  scripts/gdb/linux/tasks.py        |  19 ++
>>  scripts/gdb/linux/utils.py        |  15 ++
>>  scripts/gdb/vmlinux-gdb.py        |   2 +
>>  11 files changed, 724 insertions(+), 13 deletions(-)
>>  create mode 100644 scripts/gdb/linux/constants.py.in
>>  create mode 100644 scripts/gdb/linux/radixtree.py
>>
> 
> Besides the required rebase and, thus, the missing adjustment of the cpu
> masks, I only have minor remarks. Maybe I will have more once I can play
> with lx-interrupts ;).

Ok - well it's fixed up locally, it's just a matter of prefixing the
strings with two underscores. I should be able to get the updated
patches out soon I hope.

> However, I have a growing concern - I think we already discussed this
> offline: Without automated tests, all these helpers may quickly fall
> apart as the kernel changes. This should not block these patches, but
> maybe you can think about some testing approaches before we have dozens
> of helpers which can only be validated manually.

Yes, indeed - and the breakage already seen between v4.4 and v4.5 only
solidifies the need!

I was able to chat to a few of the Linaro LAVA guys on this topic while
I was at Connect, and they already have virtual kernels being boot
tested. This should provide a good infrastructure to run some automated
tests on.

So we have the infrastructure - we just need to get the tests written,
and included.

--
Kieran

> Thanks,
> Jan
>