Re: [LTP] mem/min_free_kbytes: Fix incorrect pass/fail accounting

[linuxtestproject.agent@gmail.com]

Hi Sachin,

On Wed, 08 Jul 2026 18:12:05 +0530, Sachin Sant wrote:
> mem/min_free_kbytes: Fix incorrect pass/fail accounting

> @@ -57,8 +57,7 @@ static void min_free_kbytes_test(void)
>  	pid = SAFE_FORK();
>  	if (pid == 0) {
>  		/* startup the check monitor */
> -		check_monitor();
> -		exit(0);
> +		exit(check_monitor());
>  	}

> +	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
> +		if (WIFEXITED(status) && WEXITSTATUS(status) == 1)
> +			tst_res(TFAIL, "MemFree dropped below min_free_kbytes");
> +		else
> +			tst_res(TFAIL, "check_monitor child failed: %s",
> +				tst_strstatus(status));
> +	} else {
> +		tst_res(TPASS, "min_free_kbytes test pass");
> +	}

The fix works in practice, but the design trades one problem for another:
encoding pass/fail as a child exit code and interpreting it in the parent
is explicitly the pattern LTP asks to avoid.

The test already sets .forks_child = 1, so the framework's shared-memory
result propagation is active.  tst_res() calls made inside check_monitor()
are automatically visible to the parent's result accounting -- no exit-code
relay needed.

> -static void check_monitor(void)
> +static int check_monitor(void)
>  {
> +	int violated = 0;

The 'violated' flag is fine for deciding when to emit the TINFO line, but
the TPASS/TFAIL themselves should be emitted by the child rather than
signalled through exit():

  if (violated)
      tst_res(TFAIL, "MemFree dropped below min_free_kbytes");
  else
      tst_res(TPASS, "min_free_kbytes test pass");

With that, check_monitor() returns void and the child exits 0 always.
The parent's wait block only needs to guard against truly unexpected
termination (signal, unknown non-zero exit), and must not re-emit a
TPASS/TFAIL for the violation outcome:

  SAFE_KILL(pid, SIGUSR1);
  SAFE_WAITPID(pid, &status, WUNTRACED | WCONTINUED);

  if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
      tst_res(TFAIL, "check_monitor child failed: %s",
          tst_strstatus(status));
  /* pass/fail already reported by the child */

This also solves the original double-accounting bug because the parent
no longer emits any result for the monitor outcome at all.

Verdict - Needs revision

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