Re: [PATCH v2] perf symbol: Remove psw_idle() from list of idle symbols

[Arnaldo Melo]

On February 23, 2026 6:46:21 PM GMT-03:00, Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>On Thu, Feb 19, 2026 at 12:38:50PM +0100, Thomas Richter wrote:
>> Commit fa2ae4a377c0 ("s390/idle: Rewrite psw_idle() in C")
>> 
>> removes symbols psw_idle() and psw_idle_exit() from the linux
>> kernel for s390. Remove them in perf tool's list of idle
>> functions. They can not be detected anymore.
>
>But I think old kernels may still run somewhere.  It seems the above
>commit was merged to v6.10.  Maybe we should wait some more time before
>removing it in the tool.

Right, people keep asking if one can use a new version of perf on an old kernel and vice versa. 

So I think we should not apply this patch. 

There has been efforts in the past to try to have have some info per sample indicating the "context" for a sample, if it was in idle processing, hard/soft irq processing, etc, but that didn't come to fruition so far. 

With that we could get rid of this flaky heuristic of looking at a symbol name.

- Arnaldo


>
>Thanks,
>Namhyung
>
>> 
>> Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>
>> Suggested-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
>> ---
>>  tools/perf/util/symbol.c | 2 --
>>  1 file changed, 2 deletions(-)
>> 
>> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
>> index 814f960fa8f8..575951d98b1b 100644
>> --- a/tools/perf/util/symbol.c
>> +++ b/tools/perf/util/symbol.c
>> @@ -752,8 +752,6 @@ static bool symbol__is_idle(const char *name)
>>  		"poll_idle",
>>  		"ppc64_runlatch_off",
>>  		"pseries_dedicated_idle_sleep",
>> -		"psw_idle",
>> -		"psw_idle_exit",
>>  		NULL
>>  	};
>>  	int i;
>> -- 
>> 2.53.0
>> 

- Arnaldo