Re: [PATCH 1/2] perf test python: Robustify the 'perf test python' test case
From: Ian Rogers
Date: Mon Nov 04 2024 - 16:00:13 EST
On Mon, Nov 4, 2024 at 10:00 AM Arnaldo Carvalho de Melo
<acme@xxxxxxxxxx> wrote:
>
> From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>
> While working on a patch to not build the 'perf test' entry that tests
> the python binding when NO_LIBPYTHON=1 is used when building perf,
> meaning that the python binding will not be built, thus no need to test
> it, I noticed this inconsistency:
>
> $ perf test 17
> 17: 'import perf' in python : Ok
> $ perf test -F 17
> 17: 'import perf' in python : Ok
> $
> $ perf check feature libpython
> libpython: [ OFF ] # HAVE_LIBPYTHON_SUPPORT
> $ ldd ~/bin/perf | grep python
> $
>
> Even without any python binding or support for loading it present in
> perf, it says that testing that feature somehow "passes":
>
> $ strace -s1024 -f -e execve perf test 17
> execve("/home/acme/bin/perf", ["perf", "test", "17"], 0x7ffe99ae5d50 /* 38 vars */) = 0
> strace: Process 519319 attached
> 17: 'import perf' in python : Running (1 active)
> strace: Process 519320 attached
> [pid 519320] execve("/bin/sh", ["sh", "-c", "--", "echo \"import sys ; sys.path.insert(0, '/tmp/build/perf-tools-next/python'); import perf\" | 2> /dev/null"], 0x377ba9a0 /* 40 vars */) = 0
> strace: Process 519321 attached
> strace: Process 519322 attached
> [pid 519321] +++ exited with 0 +++
> [pid 519322] +++ exited with 0 +++
> [pid 519320] --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=519321, si_uid=1000, si_status=0, si_utime=0, si_stime=0} ---
> [pid 519320] +++ exited with 0 +++
> [pid 519319] --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=519320, si_uid=1000, si_status=0, si_utime=0, si_stime=0} ---
> [pid 519319] +++ exited with 0 +++
> 17: 'import perf' in python : Ok
> +++ exited with 0 +++
> $
>
> It doesn't matter if we fork a new perf process to run just that test
> entry or if we don't:
>
> $ perf test -h -F
>
> Usage: perf test [<options>] [{list <test-name-fragment>|[<test-name-fragments>|<test-numbers>]}]
>
> -F, --dont-fork Do not fork for testcase
> $
>
> $ strace -s1024 -f -e execve perf test -F 17
> execve("/home/acme/bin/perf", ["perf", "test", "-F", "17"], 0x7ffda8fafed8 /* 38 vars */) = 0
> strace: Process 519336 attached
> [pid 519336] execve("/bin/sh", ["sh", "-c", "--", "echo \"import sys ; sys.path.insert(0, '/tmp/build/perf-tools-next/python'); import perf\" | 2> /dev/null"], 0x159d99a0 /* 40 vars */) = 0
> strace: Process 519337 attached
> strace: Process 519338 attached
> [pid 519337] +++ exited with 0 +++
> [pid 519338] +++ exited with 0 +++
> [pid 519336] --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=519337, si_uid=1000, si_status=0, si_utime=0, si_stime=0} ---
> [pid 519336] +++ exited with 0 +++
> --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=519336, si_uid=1000, si_status=0, si_utime=0, si_stime=0} ---
> 17: 'import perf' in python : Ok
> +++ exited with 0 +++
> $
>
> The system() call (that execve) will return zero even with that echo
> being piped into nothing:
>
> # sh -c -- echo \"import sys ; sys.path.insert(0, '/tmp/build/perf-tools-next/python'); import perf\" | 2> /dev/null
> -bash: syntax error near unexpected token `0,'
> # echo $?
> 2
> # sh -c -- echo \"import sys ; sys.path.insert(0, '/tmp/build/perf-tools-next/python'); import perf\" |
> -bash: syntax error near unexpected token `0,'
> # echo $?
> 2
> #
>
> If we instead avoid the echo and use 'python -c' to pass that simple
> python script just trying to load the non-existent perf binding we get
> less processes and a more consistent result even in this pathological
> case where PYTHON="":
>
> $ perf test 17
> 17: 'import perf' in python : FAILED!
> $ perf test -F 17
> 17: 'import perf' in python : FAILED!
> $
> $ perf test -vv 17
> Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc
> 17: 'import perf' in python:
> --- start ---
> test child forked, pid 522859
> python usage test: " -c "import sys ; sys.path.insert(0, '/tmp/build/perf-tools-next/python'); import perf" "
> sh: line 1: -c: command not found
> ---- end(-1) ----
> 17: 'import perf' in python : FAILED!
> $
>
> The next patch will sidestep all this by plain not building the python
> binding test when the binding isn't built, i.e. with NO_LIBPYTHON=1.
>
> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Cc: Athira Rajeev <atrajeev@xxxxxxxxxxxxxxxxxx>
> Cc: Howard Chu <howardchu95@xxxxxxxxx>
> Cc: Ian Rogers <irogers@xxxxxxxxxx>
> Cc: James Clark <james.clark@xxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> Cc: Leo Yan <leo.yan@xxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: Thomas Richter <tmricht@xxxxxxxxxxxxx>
> Cc: Veronika Molnarova <vmolnaro@xxxxxxxxxx>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Fwiw, I found the commit message overly long.
Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
Thanks,
Ian
> ---
> tools/perf/tests/python-use.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/tests/python-use.c b/tools/perf/tests/python-use.c
> index 0ebc22ac8d5b47ed..b7325caad22bab10 100644
> --- a/tools/perf/tests/python-use.c
> +++ b/tools/perf/tests/python-use.c
> @@ -14,8 +14,8 @@ static int test__python_use(struct test_suite *test __maybe_unused, int subtest
> char *cmd;
> int ret;
>
> - if (asprintf(&cmd, "echo \"import sys ; sys.path.insert(0, '%s'); import perf\" | %s %s",
> - PYTHONPATH, PYTHON, verbose > 0 ? "" : "2> /dev/null") < 0)
> + if (asprintf(&cmd, "%s -c \"import sys ; sys.path.insert(0, '%s'); import perf\" %s",
> + PYTHON, PYTHONPATH, verbose > 0 ? "" : "2> /dev/null") < 0)
> return -1;
>
> pr_debug("python usage test: \"%s\"\n", cmd);
> --
> 2.47.0
>