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From:   Marco Elver <elver@google.com>
Date:   Tue, 18 Jan 2022 12:40:04 +0100
Message-ID: <CANpmjNMPoU+1b1fKFuYDYwisW2YfjQHxGt5hgLp1tioG7C2jmg@mail.gmail.com>
Subject: Re: [PATCH] perf test: Test 73 Sig_trap fails on s390
To:     Leo Yan <leo.yan@linaro.org>
Cc:     John Garry <john.garry@huawei.com>,
        Thomas Richter <tmricht@linux.ibm.com>,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        acme@kernel.org, svens@linux.ibm.com, gor@linux.ibm.com,
        sumanthk@linux.ibm.com, hca@linux.ibm.com,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>
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On Tue, 18 Jan 2022 at 10:18, Leo Yan <leo.yan@linaro.org> wrote:
>
> On Mon, Jan 17, 2022 at 03:39:10PM +0000, John Garry wrote:
> > On 16/12/2021 15:48, Marco Elver wrote:
> >
> > +
> >
> > > On Thu, 16 Dec 2021 at 16:15, Thomas Richter<tmricht@linux.ibm.com>  wrote:
> > > > In Linux next kernel
> > > > Commit 5504f67944484 ("perf test sigtrap: Add basic stress test for sigtrap handling")
> > > > introduced the new test which uses breakpoint events.
> > > > These events are not supported on s390 and PowerPC and always fail:
> > > >
> > > >   # perf test -F 73
> > > >   73: Sigtrap                                                         : FAILED!
> > > >   #
> > > >
> > > > Fix it the same way as in the breakpoint tests in file
> > > > tests/bp_account.c where these type of tests are skipped on
> > > > s390 and PowerPC platforms.
> > > >
> > > > With this patch skip this test on both platforms.
> > > >
> > > > Output after:
> > > >   # ./perf test -F 73
> > > >   73: Sigtrap
> > > >
> > > > Fixes: 5504f67944484 ("perf test sigtrap: Add basic stress test for sigtrap handling")
> > > >
> > > > Cc: Marco Elver<elver@google.com>
> > > > Signed-off-by: Thomas Richter<tmricht@linux.ibm.com>
> > > Acked-by: Marco Elver<elver@google.com>
> > >
> > > Thanks, and sorry for missing this case!
> > >
> >
> > I am finding that this test hangs on my arm64 machine:
> >
> > john@debian:~/kernel-dev2/tools/perf$ sudo ./perf test -vvv 73
> >  73: Sigtrap:
> > --- start ---
> > test child forked, pid 45193
>
> Both Arm and Arm64 platforms cannot support signal handler with
> breakpoint, please see the details in [1].  So I think we need
> something like below:
>
> static int test__sigtrap(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
> {
>         ...
>
>         if (!BP_SIGNAL_IS_SUPPORTED) {
>                 pr_debug("Test not supported on this architecture");
>                 return TEST_SKIP;
>         }
>
>         ...
> }
>
> Since we have defined BP_SIGNAL_IS_SUPPORTED, I think we can reuse it at
> here.
>
> [1] https://lore.kernel.org/lkml/157169993406.29376.12473771029179755767.tip-bot2@tip-bot2/

Does this limitation also exist for address watchpoints? The sigtrap
test does not make use of instruction breakpoints, but instead just
sets up a watchpoint on access to a data address.

Thanks,
-- Marco