linux-kernel - Re: [PATCH] perf test: Skip Sigtrap test for arm+aarch64

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Date:   Thu, 17 Feb 2022 17:34:23 +0000
From:   John Garry <john.garry@...wei.com>
To:     Marco Elver <elver@...gle.com>
CC:     <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
        <mark.rutland@....com>, <jolsa@...nel.org>, <namhyung@...nel.org>,
        <leo.yan@...aro.org>, <dvyukov@...gle.com>, <will@...nel.org>,
        <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux@...linux.org.uk>,
        <irogers@...gle.com>, Thomas Richter <tmricht@...ux.ibm.com>
Subject: Re: [PATCH] perf test: Skip Sigtrap test for arm+aarch64

On 17/02/2022 16:45, Marco Elver wrote:
> On Thu, 17 Feb 2022 at 17:28, John Garry <john.garry@...wei.com> wrote:

+ Ian, Thomas

>>
>> Skip the Sigtrap test for arm + arm64, same as was done for s390 in
>> commit a840974e96fd ("perf test: Test 73 Sig_trap fails on s390").
>>
>> As described by Will at [0], in the test we get stuck in a loop of handling
>> the HW breakpoint exception and never making progress. GDB handles this
>> by stepping over the faulting instruction, but with perf the kernel is
>> expected to handle the step (which it doesn't for arm).
>>
>> Dmitry made an attempt to get this work, also mentioned in the same thread
>> as [0], which was appreciated. But the best thing to do is skip the test
>> for now.
>>
>> [0] https://lore.kernel.org/linux-perf-users/20220118124343.GC98966@leoy-ThinkPad-X240s/T/#m13b06c39d2a5100d340f009435df6f4d8ee57b5a
>>
>> Fixes: Fixes: 5504f67944484 ("perf test sigtrap: Add basic stress test for sigtrap handling")
>> Signed-off-by: John Garry <john.garry@...wei.com>
>>
>> diff --git a/tools/perf/tests/sigtrap.c b/tools/perf/tests/sigtrap.c
>> index 1f147fe6595f..3f0b5c1398b5 100644
>> --- a/tools/perf/tests/sigtrap.c
>> +++ b/tools/perf/tests/sigtrap.c
>> @@ -29,7 +29,8 @@
>>    * Just disable the test for these architectures until these issues are
>>    * resolved.
>>    */
>> -#if defined(__powerpc__) || defined(__s390x__)
>> +#if defined(__powerpc__) || defined(__s390x__) || \
>> +       defined(__arm__) || defined(__aarch64__)
>>   #define BP_ACCOUNT_IS_SUPPORTED 0
>>   #else
>>   #define BP_ACCOUNT_IS_SUPPORTED 1
> 
> This is now equivalent to BP_SIGNAL_IS_SUPPORTED
> tools/perf/tests/tests.h -- and different from the original
> BP_ACCOUNT_IS_SUPPORTED (and makes me wonder why
> BP_SIGNAL_IS_SUPPORTED wasn't just used from the beginning). Perhaps
> just use BP_SIGNAL_IS_SUPPORTED.
> 

We currently have BP_ACCOUNT_IS_SUPPORTED defined now in 2x locations:

tests/sigtrap.c
tests/bp_account.c

bp_account works for arm64, and we don't want to skip that test. So, as 
long as the macro meaning is appropriate, we can reuse 
BP_SIGNAL_IS_SUPPORTED for sigtrap.c

Thanks,
John