linux-kernel - Re: [PATCH v4 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

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Date:   Thu, 1 Dec 2022 10:12:29 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     "Shaopeng Tan (Fujitsu)" <tan.shaopeng@...itsu.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>,
        "Shuah Khan" <skhan@...uxfoundation.org>
Subject: Re: [PATCH v4 4/5] selftests/resctrl: Cleanup properly when an error
 occurs in CAT test

Hi Shaopeng,

On 12/1/2022 12:20 AM, Shaopeng Tan (Fujitsu) wrote:
> Hi Reinette,
> 
>> On 11/30/2022 12:32 AM, Shaopeng Tan (Fujitsu) wrote:
>>
>>> Removing ctrl_handler() is only part of the fix in the next version(v5).
>>> All fixes as follows.
>>>
>>> --- a/tools/testing/selftests/resctrl/cat_test.c
>>> +++ b/tools/testing/selftests/resctrl/cat_test.c
>>> @@ -98,12 +98,17 @@ void cat_test_cleanup(void)
>>>         remove(RESULT_FILE_NAME2);
>>>  }
>>>
>>> +static void ctrlc_handler_child(int signum, siginfo_t *info, void
>>> +*ptr) {
>>> +       exit(EXIT_SUCCESS);
>>> +}
>>> +
>>
>> Could you please elaborate why this is necessary?
> 
> If enter "ctrl-c" when running "resctrl_tests -t cat",
> SIGINT will be sent to all processes (parent&child).
> 
> At this time, the child process receives a SIGINT signal, but does not take any action.
> In this case the parent process may not call ctrlc_handler() as expected.

Apologies, but I am not able to follow. My understanding is that the
ideal in working an failing case is for the parent to kill the child.
Could you please elaborate why the ctrlc_handler() may not be called?

> Therefore, ctrlc_handler_child() is necessary.
> 
> It may be better to ignore the signal, then code can be simple as follows.
> ----
>         if (bm_pid == 0) {
>                 param.mask = l_mask_1;
>                 strcpy(param.ctrlgrp, "c1");
>                 strcpy(param.mongrp, "m1");
>                 param.span = cache_size * n / count_of_bits;
>                 strcpy(param.filename, RESULT_FILE_NAME1);
>                 param.num_of_runs = 0;
>                 param.cpu_no = sibling_cpu_no;
>                 /* Ignore the signal,and wait to be cleaned up by the parent process */
>                 sigfillset(&sigact.sa_mask);
>                 sigact.sa_handler = SIG_IGN;
>                 //sigact.sa_sigaction = ctrlc_handler_child;  //delete
>                 if (sigaction(SIGINT, &sigact, NULL) ||
>                     sigaction(SIGTERM, &sigact, NULL) ||
>                     sigaction(SIGHUP, &sigact, NULL))
>                         perror("# sigaction");
>         } else {

Reinette