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Subject: Re: [PATCH 5/5] perf arm-spe: Snapshot mode test
To:     Leo Yan <leo.yan@linaro.org>, German Gomez <german.gomez@arm.com>
Cc:     linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        John Garry <john.garry@huawei.com>,
        Will Deacon <will@kernel.org>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Mike Leach <mike.leach@linaro.org>,
        linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org
References: <20210916154635.1525-1-german.gomez@arm.com>
 <20210916154635.1525-5-german.gomez@arm.com>
 <20211020131339.GG49614@leoy-ThinkPad-X240s>
From:   James Clark <james.clark@arm.com>
Message-ID: <fd65eb63-d4ca-2105-74cb-c717ad2eb7d3@arm.com>
Date:   Tue, 2 Nov 2021 14:07:42 +0000
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On 20/10/2021 14:13, Leo Yan wrote:
> On Thu, Sep 16, 2021 at 04:46:35PM +0100, German Gomez wrote:
>> Shell script test_arm_spe.sh has been added to test the recording of SPE
>> tracing events in snapshot mode.
>>
>> Reviewed-by: James Clark <james.clark@arm.com>
>> Signed-off-by: German Gomez <german.gomez@arm.com>
>> ---
>>  tools/perf/tests/shell/test_arm_spe.sh | 91 ++++++++++++++++++++++++++
>>  1 file changed, 91 insertions(+)
>>  create mode 100755 tools/perf/tests/shell/test_arm_spe.sh
>>
>> diff --git a/tools/perf/tests/shell/test_arm_spe.sh b/tools/perf/tests/shell/test_arm_spe.sh
>> new file mode 100755
>> index 000000000000..9ed817e76f95
>> --- /dev/null
>> +++ b/tools/perf/tests/shell/test_arm_spe.sh
>> @@ -0,0 +1,91 @@
>> +#!/bin/sh
>> +# Check Arm SPE trace data recording and synthesized samples
>> +
>> +# Uses the 'perf record' to record trace data of Arm SPE events;
>> +# then verify if any SPE event samples are generated by SPE with
>> +# 'perf script' and 'perf report' commands.
>> +
>> +# SPDX-License-Identifier: GPL-2.0
>> +# German Gomez <german.gomez@arm.com>, 2021
>> +
>> +skip_if_no_arm_spe_event() {
>> +	perf list | egrep -q 'arm_spe_[0-9]+//' && return 0
>> +
>> +	# arm_spe event doesn't exist
>> +	return 2
>> +}
>> +
>> +skip_if_no_arm_spe_event || exit 2
>> +
>> +perfdata=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
>> +glb_err=0
>> +
>> +cleanup_files()
>> +{
>> +	rm -f ${perfdata}
>> +	trap - exit term int
>> +	kill -2 $$ # Forward sigint to parent
> 
> I understand you copy this code from Arm cs-etm testing, but I found
> the sentence 'kill -2 $$' will cause a failure at my side with the
> command:
> 
> root@ubuntu:/home/leoy/linux/tools/perf# ./perf test 85 -v
> 85: Check Arm SPE trace data recording and synthesized samples      :
> --- start ---
> test child forked, pid 29053
> Recording trace with snapshot mode /tmp/__perf_test.perf.data.uughb
> Looking at perf.data file for dumping samples:
> Looking at perf.data file for reporting samples:
> SPE snapshot testing: PASS
> test child finished with -1
> ---- end ----
> Check Arm SPE trace data recording and synthesized samples: FAILED!
> 
> I changed to use below code and looks it works for me:
> 
>         if [[ "$1" == "int" ]]; then
>                 kill -SIGINT $$
>         fi
>         if [[ "$1" == "term" ]]; then
>                 kill -SIGTERM $$
>         fi
> 
> Thanks,
> Leo

This is quite interesting. It looks like the issue is caused by the update from dash 0.5.8
on Ubuntu 18 to dash 0.5.10 on Ubuntu 20. Specifically the commit that causes the issue is:

   commit 9e5cd41d9605e4caaac3aacdc0482f6ee220a298
   Author: Herbert Xu <herbert@gondor.apana.org.au>
   Date:   Mon May 7 00:40:34 2018 +0800

    jobs - Do not block when waiting on SIGCHLD
    
    Because of the nature of SIGCHLD, the process may have already been
    waited on and therefore we must be prepared for the case that wait
    may block.  So ensure that it doesn't by using WNOHANG.
    
    Furthermore, multiple jobs may have exited when gotsigchld is set.
    Therefore we need to wait until there are no zombies left.
    
    Lastly, waitforjob needs to be called with interrupts off and
    the original patch broke that.
    
    Fixes: 03876c0743a5 ("eval: Reap zombies after built-in...")
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>


This also means that the Coresight shell test will not be working anymore because I added
the same trap to it so that it could be run in a loop. I'm going to compare the bahaviour
to bash to see which one is doing the right thing and what the correct change to make to 
fix it is. Or a bug needs to be reported.

Thanks
James

> 
>> +	exit $glb_err
>> +}
>> +
>> +trap cleanup_files exit term int
>> +
>> +arm_spe_report() {
>> +	if [ $2 != 0 ]; then
>> +		echo "$1: FAIL"
>> +		glb_err=$2
>> +	else
>> +		echo "$1: PASS"
>> +	fi
>> +}
>> +
>> +perf_script_samples() {
>> +	echo "Looking at perf.data file for dumping samples:"
>> +
>> +	# from arm-spe.c/arm_spe_synth_events()
>> +	events="(ld1-miss|ld1-access|llc-miss|lld-access|tlb-miss|tlb-access|branch-miss|remote-access|memory)"
>> +
>> +	# Below is an example of the samples dumping:
>> +	#	dd  3048 [002]          1    l1d-access:      ffffaa64999c __GI___libc_write+0x3c (/lib/aarch64-linux-gnu/libc-2.27.so)
>> +	#	dd  3048 [002]          1    tlb-access:      ffffaa64999c __GI___libc_write+0x3c (/lib/aarch64-linux-gnu/libc-2.27.so)
>> +	#	dd  3048 [002]          1        memory:      ffffaa64999c __GI___libc_write+0x3c (/lib/aarch64-linux-gnu/libc-2.27.so)
>> +	perf script -F,-time -i ${perfdata} 2>&1 | \
>> +		egrep " +$1 +[0-9]+ .* +${events}:(.*:)? +" > /dev/null 2>&1
>> +}
>> +
>> +perf_report_samples() {
>> +	echo "Looking at perf.data file for reporting samples:"
>> +
>> +	# Below is an example of the samples reporting:
>> +	#   73.04%    73.04%  dd    libc-2.27.so      [.] _dl_addr
>> +	#    7.71%     7.71%  dd    libc-2.27.so      [.] getenv
>> +	#    2.59%     2.59%  dd    ld-2.27.so        [.] strcmp
>> +	perf report --stdio -i ${perfdata} 2>&1 | \
>> +		egrep " +[0-9]+\.[0-9]+% +[0-9]+\.[0-9]+% +$1 " > /dev/null 2>&1
>> +}
>> +
>> +arm_spe_snapshot_test() {
>> +	echo "Recording trace with snapshot mode $perfdata"
>> +	perf record -o ${perfdata} -e arm_spe// -S \
>> +		-- dd if=/dev/zero of=/dev/null > /dev/null 2>&1 &
>> +	PERFPID=$!
>> +
>> +	# Wait for perf program
>> +	sleep 1
>> +
>> +	# Send signal to snapshot trace data
>> +	kill -USR2 $PERFPID
>> +
>> +	# Stop perf program
>> +	kill $PERFPID
>> +	wait $PERFPID
>> +
>> +	perf_script_samples dd &&
>> +	perf_report_samples dd
>> +
>> +	err=$?
>> +	arm_spe_report "SPE snapshot testing" $err
>> +}
>> +
>> +arm_spe_snapshot_test
>> +exit $glb_err
>> \ No newline at end of file
>> -- 
>> 2.17.1
>>