linux-kernel - RE: [PATCH 4/5] selftests/resctrl: Kill the child process before exiting the parent process if an exception occurs

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Date:   Tue, 27 Sep 2022 09:02:07 +0000
From:   "tan.shaopeng@...itsu.com" <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 4/5] selftests/resctrl: Kill the child process before
 exiting the parent process if an exception occurs

Hi Reinette,

> On 9/13/2022 6:51 PM, Shaopeng Tan wrote:
> 
> ...
> 
> > @@ -218,11 +219,11 @@ int cat_perf_miss_val(int cpu_no, int n, char
> *cache_type)
> >  			}
> >  		}
> >  		close(pipefd[0]);
> > -		kill(bm_pid, SIGKILL);
> >  	}
> >
> > -	if (bm_pid)
> > -		umount_resctrlfs();
> > +out:
> > +	kill(bm_pid, SIGKILL);
> > +	umount_resctrlfs();
> >
> 
> From what I can tell both parent and child will now run this code. So both will
> attempt to unmount resctrl fs and the child will attempt to kill PID 0?

Thanks for your advice. There are problems as you point out.
I think it is complicated if we fix this bug like MBM/MBA/CMT test using sigaction().
It seems this bug cannot be solved easily.
Please give me some time.

Best Regards,
Shaopeng