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From:   Marco Elver <elver@google.com>
Date:   Fri, 18 Feb 2022 10:44:15 +0100
Message-ID: <CANpmjNMVz0VoBvV74AJhCYoP5yVad0JwOpY47YhUrqsZqF7NZw@mail.gmail.com>
Subject: Re: [PATCH v2] perf test: Skip Sigtrap test for arm+aarch64
To:     John Garry <john.garry@huawei.com>
Cc:     peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
        mark.rutland@arm.com, jolsa@kernel.org, namhyung@kernel.org,
        leo.yan@linaro.org, dvyukov@google.com, will@kernel.org,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux@armlinux.org.uk,
        tmricht@linux.ibm.com, irogers@google.com
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On Fri, 18 Feb 2022 at 10:39, John Garry <john.garry@huawei.com> wrote:
>
> 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"). For
> this, reuse BP_SIGNAL_IS_SUPPORTED - meaning that the arch can use BP to
> generate signals - instead of BP_ACCOUNT_IS_SUPPORTED, which is
> appropriate.
>
> 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@huawei.com>

Acked-by: Marco Elver <elver@google.com>

Thanks !

> diff --git a/tools/perf/tests/sigtrap.c b/tools/perf/tests/sigtrap.c
> index 1f147fe6595f..e32ece90e164 100644
> --- a/tools/perf/tests/sigtrap.c
> +++ b/tools/perf/tests/sigtrap.c
> @@ -22,19 +22,6 @@
>  #include "tests.h"
>  #include "../perf-sys.h"
>
> -/*
> - * PowerPC and S390 do not support creation of instruction breakpoints using the
> - * perf_event interface.
> - *
> - * Just disable the test for these architectures until these issues are
> - * resolved.
> - */
> -#if defined(__powerpc__) || defined(__s390x__)
> -#define BP_ACCOUNT_IS_SUPPORTED 0
> -#else
> -#define BP_ACCOUNT_IS_SUPPORTED 1
> -#endif
> -
>  #define NUM_THREADS 5
>
>  static struct {
> @@ -135,7 +122,7 @@ static int test__sigtrap(struct test_suite *test __maybe_unused, int subtest __m
>         char sbuf[STRERR_BUFSIZE];
>         int i, fd, ret = TEST_FAIL;
>
> -       if (!BP_ACCOUNT_IS_SUPPORTED) {
> +       if (!BP_SIGNAL_IS_SUPPORTED) {
>                 pr_debug("Test not supported on this architecture");
>                 return TEST_SKIP;
>         }
> --
> 2.26.2
>