[Mesa-dev] [PATCH 2/2] gallium/util: libunwind support

[Rob Clark]

On Tue, Apr 4, 2017 at 6:28 AM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> On 4 April 2017 at 10:00, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>> On 04/03/2017 11:09 PM, Rob Clark wrote:
>>> On Mon, Apr 3, 2017 at 4:57 PM, Rob Clark <robdclark at gmail.com> wrote:
>>>> On Mon, Apr 3, 2017 at 4:06 PM, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>>>>> On 04/03/2017 07:33 PM, Thomas Hellstrom wrote:
>>>>>> On 04/03/2017 07:13 PM, Rob Clark wrote:
>>>>>>> On Mon, Apr 3, 2017 at 12:56 PM, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>>>>>>>> Hi, Rob,
>>>>>>>>
>>>>>>>> On 03/24/2017 10:21 PM, Rob Clark wrote:
>>>>>>>>> It's kinda sad that (a) we don't have debug_backtrace support on !X86
>>>>>>>>> and that (b) we re-invent our own crude backtrace support in the first
>>>>>>>>> place.  If available, use libunwind instead.  The backtrace format is
>>>>>>>>> based on what xserver and weston use, since it is nice not to have to
>>>>>>>>> figure out a different format.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Rob Clark <robdclark at gmail.com>
>>>>>>>> Did you consider glibc "backtrace()", I think it's also available on ARM...
>>>>>>> I had not.. although xserver and weston are already using libunwind.
>>>>>>> I'm not sure about portability of libunwind to other libc
>>>>>>> implementations (but I guess it is at least not worse than using a
>>>>>>> glibc specific API).
>>>>>>>
>>>>>>> I suppose we could always add a fallback to backtrace().
>>>>>>>
>>>>> Hmm. This commit (bisected) appears to break svga/vmwgfx in DEBUG mode:
>>>>>
>>>>> *** Error in `glxgears': malloc(): memory corruption: 0x00000000025c09c0 ***
>>>>> Aborted (core dumped)
>>>>>
>>>>> The svga linux winsys makes extensive use of the backtrace functionality
>>>>> using u_debug_flush.c
>>>> ok, I can reproduce.. hopefully patch following shortly..
>>>>
>>> So, I found one other minor issue, but the big problem is
>>> debug_stack_frame size difference, because u_debug_flush.c doesn't
>>> #include config.h..  adding:
>>>
>>> #ifdef HAVE_CONFIG_H
>>> #include <config.h>
>>> #endif
>> Hmm,
>>
>> Actually it seems we don't have a config.h, but rather -DHAVE_LIBUNWIND
>> is included in the compile command.
>
> That's correct. HAVE_CONFIG_H is never defined and the only config.h
> file we have is completely unrelated. Thus I'm not sure how the above
> ifdef hunk helped anyone.
>


hmm.. odd.. unless touching the .h file somehow triggered something to
recompile?  That was definitely the last change I made before it
stopped crashing.  But possibly something got out of whack with
timestamps or something on my end.

BR,
-R