Re: [PATCH 0/4] Modernize frame unwinders and add disable feature

[Luis Machado <luis.machado@arm.com>]

On 3/13/24 12:08, Guinevere Larsen wrote:
> On 11/03/2024 16:10, Luis Machado wrote:
>> On 3/11/24 15:00, Guinevere Larsen wrote:
>>> On 11/03/2024 15:56, Luis Machado wrote:
>>>> Hi,
>>>>
>>>> On 3/6/24 12:51, Guinevere Larsen wrote:
>>>>> This patch series started with me trying to make it easier to test GDB's
>>>>> ability to unwind using CFI data, to improve a previous patch I sent to
>>>>> the list. However, once I finished these changes, I realized there was
>>>>> an unrelated bug I should fix before proposing the CFI test. Since these
>>>>> changes are significant enough already, and I think would be interesting
>>>>> on their own, I figured I shoudl submit this patch series as is right
>>>>> now while I figure out the other bug.
>>>>>
>>>>> The first patch is just a minor change, storing frame unwinders in a
>>>>> vector instead of through an unwinder table accessible using the
>>>>> registry system. This isn't required (like I originally thought it was),
>>>>> but it does make the whole system more readable in my opinion.
>>>>>
>>>>> Patch 3 has the real meat of the modernization, making GDB use
>>>>> polymorphism to handle frame unwinders. This is slightly slower than
>>>>> using function pointers, but much more readable in my opinion.
>>>>>
>>>>> As for the unwinder classes, they were chosen somewhat arbitrarily,
>>>>> mostly based on where I found an unwinder and its name. I almost expect
>>>>> some unwinders to be mis-categorized, but that should be easy to fix.
>>>>>
>>>>> The changes up to patch 3 have been tested with a try-branch, no
>>>>> regressions as far as I could see.
>>>>>
>>>>> Guinevere Larsen (4):
>>>>>     gdb: make gdbarch store a vector of frame unwinders
>>>>>     gdb: add "unwinder class" to frame unwinders
>>>>>     gdb: Migrate frame unwinders to use C++ classes
>>>>>     GDB: introduce ability to disable frame unwinders
>>>> I haven't gone through the series in detail, but I thought I'd give it a try on one of the
>>>> aarch64 machines I have access to. I didn't look particularly healthy:
>>>>
>>>>
>>>> # of unexpected core files      47
>>>> # of expected passes            116521
>>>> # of unexpected failures        581
>>>> # of expected failures          77
>>>> # of known failures             116
>>>> # of untested testcases         128
>>>> # of unresolved testcases       1102
>>>> # of unsupported tests          458
>>>> # of duplicate test names       10
>>>>
>>>> I see a number of internal errors going on. Mostly like these:
>>>>
>>>>           ../../../repos/binutils-gdb/gdbsupport/errors.cc:58
>>>> 0xaaaad27e7877 check_ptrace_stopped_lwp_gone
>>>>           ../../../repos/binutils-gdb/gdb/linux-nat.c:1634
>>>> 0xaaaad27e7877 check_ptrace_stopped_lwp_gone
>>>>           ../../../repos/binutils-gdb/gdb/linux-nat.c:1630
>>>> 0xaaaad2ae0fa3 linux_resume_one_lwp
>>>>
>>> Oh no! Linaro CI had showed something was wrong, but I wasn't able to grab an aarch64 machine to test yet. I'll check it out when I can, thanks for narrowing it down for me
>>>
>> You're welcome. Do let me know if you can't easily find an aarch64 machine to try things on, and I can provide more info
>> and take a deeper look.
>>
> I think I found the reason why aarch64 started failing so many cases. Can you try the following change and see if it works?
> 
> I'm not 100% sure because the machine I'm using seems to have some rather unstable results, but I think it should have solved the problem.
> 

The attached fixlet completely clears things up, and the testsuite for aarch64-linux is back to normal.

# of unexpected core files      1
# of expected passes            119178
# of unexpected failures        22
# of expected failures          77
# of known failures             120
# of untested testcases         128
# of unsupported tests          458
# of duplicate test names       3