[LTP] [PATCH] futex/futex_wake04.c: fix issues with hugepages and usleep

[Cyril Hrubis]

Hi!
> This commit fixes 2 observed issues:
> 
> 1) usleep() time is too small if test is being executed in slower
> terminal devices (specially embedded systems). Raising it to 0.001
> seconds was enough to finish 10240 iterations in around 90 seconds in a
> 4 vcpu kvm guest (fully emulated serial being used as console).
> 
> 2) Test was changing number of hugepages during setup()/cleanup() phase
> despite the system had (or not) available hugepages. This was causing
> overhead of destroying (or creating) hugepages during the test
> execution.  Now, if system has > 0 hugepages available, the test doesn't
> touch it.

Can you please split this into separate patches? Generally it's
considered a good practice to split unrelated changes like these.

> Link: https://bugs.linaro.org/show_bug.cgi?id=3984
> Signed-off-by: Rafael David Tinoco <rafael.tinoco@linaro.org>
> ---
>  testcases/kernel/syscalls/futex/futex_wake04.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/testcases/kernel/syscalls/futex/futex_wake04.c b/testcases/kernel/syscalls/futex/futex_wake04.c
> index 3c7038317..93d36ac33 100644
> --- a/testcases/kernel/syscalls/futex/futex_wake04.c
> +++ b/testcases/kernel/syscalls/futex/futex_wake04.c
> @@ -76,14 +76,17 @@ static void setup(void)
>  	tst_tmpdir();
>  
>  	SAFE_FILE_SCANF(NULL, PATH_NR_HUGEPAGES, "%ld", &orig_hugepages);
> -	SAFE_FILE_PRINTF(NULL, PATH_NR_HUGEPAGES, "%d", 1);
> +
> +	if (!orig_hugepages)

Maybe <= 0 would be a bit more robust.

> +		SAFE_FILE_PRINTF(NULL, PATH_NR_HUGEPAGES, "%d", 1);
>  
>  	TEST_PAUSE;
>  }
>  
>  static void cleanup(void)
>  {
> -	SAFE_FILE_PRINTF(NULL, PATH_NR_HUGEPAGES, "%ld", orig_hugepages);
> +	if (!orig_hugepages)
> +		SAFE_FILE_PRINTF(NULL, PATH_NR_HUGEPAGES, "%d", 0);
>  
>  	tst_rmdir();
>  }
> @@ -172,8 +175,9 @@ static void wakeup_thread2(void)
>  				tst_strerrno(res));
>  	}
>  
> +	/* 0.001 seconds: less might cause lockups for slower terminals */

I would avoid comments like this, you can check the git changelog to
figure out why the value was changed.

>  	while (wait_for_threads(2))
> -		usleep(100);
> +		usleep(1000);
>  
>  	futex_wake(futex2, 1, 0);
>  
> -- 
> 2.19.1
> 

-- 
Cyril Hrubis
chrubis@suse.cz