linux-kernel - Re: [PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error occurs in CAT test

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Date:   Tue, 7 Feb 2023 16:05:04 +0200 (EET)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Shaopeng Tan <tan.shaopeng@...fujitsu.com>
cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Shuah Khan <shuah@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v6 4/5] selftests/resctrl: Cleanup properly when an error
 occurs in CAT test

On Tue, 31 Jan 2023, Shaopeng Tan wrote:

> After creating a child process with fork() in CAT test, if an error
> occurs or a signal such as SIGINT is received, the parent process will
> be terminated immediately, and therefor the child process will not
> be killed and also resctrlfs is not unmounted.
> 
> There is a signal handler registered in CMT/MBM/MBA tests, which kills
> child process, unmount resctrlfs, cleanups result files, etc., if a
> signal such as SIGINT is received.
> 
> Commonize the signal handler registered for CMT/MBM/MBA tests and reuse
> it in CAT too.
> 
> To reuse the signal handler, make the child process in CAT wait to be
> killed by parent process in any case (an error occurred or a signal was
> received), and when killing child process use global bm_pid instead of
> local bm_pid.
> 
> Also, since the MBA/MBA/CMT/CAT are run in order, unregister the signal
> handler at the end of each test so that the signal handler cannot be
> inherited by other tests.
> 
> Signed-off-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> ---

>  	if (bm_pid == 0) {
>  		/* Tell parent that child is ready */
>  		close(pipefd[0]);
>  		pipe_message = 1;
>  		if (write(pipefd[1], &pipe_message, sizeof(pipe_message)) <
> -		    sizeof(pipe_message)) {
> -			close(pipefd[1]);
> +		    sizeof(pipe_message))
> +			/*
> +			 * Just print the error message.
> +			 * Let while(1) run and wait for itself to be killed.
> +			 */
>  			perror("# failed signaling parent process");

If the write error is ignored here, won't it just lead to parent hanging 
forever waiting for the child to send the message through the pipe which 
will never come?


-- 
 i.