linux-kernel - RE: [PATCH v5 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

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Message-ID: <TYAPR01MB6330317EADA62C45EAD8B0608BC99@TYAPR01MB6330.jpnprd01.prod.outlook.com>
Date:   Tue, 24 Jan 2023 02:16:27 +0000
From:   "Shaopeng Tan (Fujitsu)" <tan.shaopeng@...itsu.com>
To:     'Reinette Chatre' <reinette.chatre@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Shuah Khan <shuah@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
Subject: RE: [PATCH v5 4/5] selftests/resctrl: Cleanup properly when an error
 occurs in CAT test

Hi Reinette,

> On 1/22/2023 8:22 PM, Shaopeng Tan (Fujitsu) wrote:
> >> On 1/10/2023 11:58 PM, Shaopeng Tan wrote:
> 
> ...
> 
> >>> diff --git a/tools/testing/selftests/resctrl/cat_test.c
> >>> b/tools/testing/selftests/resctrl/cat_test.c
> >>> index 6a8306b0a109..87302b882929 100644
> >>> --- a/tools/testing/selftests/resctrl/cat_test.c
> >>> +++ b/tools/testing/selftests/resctrl/cat_test.c
> >>> @@ -103,7 +103,6 @@ int cat_perf_miss_val(int cpu_no, int n, char
> >> *cache_type)
> >>>  	unsigned long l_mask, l_mask_1;
> >>>  	int ret, pipefd[2], sibling_cpu_no;
> >>>  	char pipe_message;
> >>> -	pid_t bm_pid;
> >>>
> >>>  	cache_size = 0;
> >>>
> >>> @@ -181,28 +180,29 @@ int cat_perf_miss_val(int cpu_no, int n, char
> >> *cache_type)
> >>>  		strcpy(param.filename, RESULT_FILE_NAME1);
> >>>  		param.num_of_runs = 0;
> >>>  		param.cpu_no = sibling_cpu_no;
> >>> +	} else {
> >>> +		ret = signal_handler_register();
> >>> +		if (ret)
> >>> +			goto out;
> >>
> >> The "goto" will unregister the signal handler. Is that necessary if
> >> the registration failed?
> >>
> >> Also, if signal_handler_register() fails then the child will keep
> >> running and run its test ... would child not then run forever?
> >
> > A signal handler is needed here, but it is rarely used.
> > Also, the registration rarely fails.
> > Therefore, if registration failed,
> > just print a warning/info message as follow.
> > how about this idea?
> >
> > ksft_print_msg("Failed to register signal handler, signals
> > SIGINT/SIGTERM/SIGHUP will not be handled as expected");
> >
> 
> I do not think this is necessary considering that signal_handler_register()
> already prints an error on failure.
> 
> Adding an error message does not address the two issues I raised.

The previous idea was just to print a message instead of "goto".
How about the idea to keep the parent&child process running forever even if the signal handler registration fails.

+	} else {
+		signal_handler_register();
+	}

I don't think the test need stop when the signal handler registration fails,
since this signal handler is rarely used and registration of signal handlers rarely fails.

Best regards,
Shaopeng TAN