linux-kernel - Re: [PATCH 2/2] tools/perf: Fix parallel-perf python script to replace new python syntax ":=" usage

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Date: Sun, 16 Jun 2024 18:03:28 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, acme@...nel.org,
 jolsa@...nel.org, irogers@...gle.com, namhyung@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, akanksha@...ux.ibm.com, maddy@...ux.ibm.com,
 kjain@...ux.ibm.com, disgoel@...ux.vnet.ibm.com
Subject: Re: [PATCH 2/2] tools/perf: Fix parallel-perf python script to
 replace new python syntax ":=" usage

On 14/06/24 20:27, Athira Rajeev wrote:
> perf test "perf script tests" fails as below in systems
> with python 3.6
> 
> 	File "/home/athira/linux/tools/perf/tests/shell/../../scripts/python/parallel-perf.py", line 442
> 	if line := p.stdout.readline():
>              ^
> 	SyntaxError: invalid syntax
> 	--- Cleaning up ---
> 	---- end(-1) ----
> 	92: perf script tests: FAILED!
> 
> This happens because ":=" is a new syntax that assigns values
> to variables as part of a larger expression. This is introduced
> from python 3.8 and hence fails in setup with python 3.6

According to below python 3.6 is end-of-life

	https://devguide.python.org/versions/

What was still using python 3.6?

> Address this by splitting the large expression and check the
> value in two steps:
> Previous line: if line := p.stdout.readline():
> Current change:
> 	line = p.stdout.readline()
> 	if line:
> 
> With patch
> 
> 	./perf test "perf script tests"
> 	 93: perf script tests:  Ok
> 
> Signed-off-by: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
>  tools/perf/scripts/python/parallel-perf.py | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/scripts/python/parallel-perf.py b/tools/perf/scripts/python/parallel-perf.py
> index 21f32ec5ed46..be85fd7f6632 100755
> --- a/tools/perf/scripts/python/parallel-perf.py
> +++ b/tools/perf/scripts/python/parallel-perf.py
> @@ -439,7 +439,8 @@ def ProcessCommandOutputLines(cmd, per_cpu, fn, *x):
>  	pat = re.compile(r"\s*\[[0-9]+\]")
>  	p = subprocess.Popen(cmd, stdout=subprocess.PIPE)
>  	while True:
> -		if line := p.stdout.readline():
> +		line = p.stdout.readline()
> +		if line:
>  			line = line.decode("utf-8")
>  			if pat.match(line):
>  				line = line.split()