[LTP] [PATCH] lib/mem.c: handle the case oom0{3, 5} exit with EAGAIN situation

[Jan Stancek]

----- Original Message -----
> From: "Li Wang" <liwang@redhat.com>
> To: jstancek@redhat.com
> Cc: ltp@lists.linux.it
> Sent: Wednesday, 16 September, 2015 7:06:51 AM
> Subject: [PATCH] lib/mem.c: handle the case oom0{3,5} exit with EAGAIN situation
> 
> Sometimes oom0{3,5} failed as the following results:
> 
> oom05       0  TINFO  :  start OOM testing for mlocked pages.
> oom05       0  TINFO  :  expected victim is 3371.
> oom05       0  TINFO  :  thread (3fff788ff1c0), allocating 3221225472 bytes.
> ...
> oom05       5  TFAIL  :  mem.c:153: victim unexpectedly ended with retcode:
> 11, expected: 12
> 
> In the OOM test, that tries to consume all memory. But the test doesn't retry
> to mlock, it simply
> exits with errno returned by mlock. At the moment testcase is expecting
> either ENOMEM or getting
> killed by kernel.
> 
> Here do retry the function if mlock() fail with 'EAGAIN' errno.
> 
> Signed-off-by: Li Wang <liwang@redhat.com>
> Signed-off-by: Jan Stancek <jstancek@redhat.com>

Hi,

Please don't include my "Signed-off-by" for patches I haven't written/modified.

> ---
>  testcases/kernel/mem/lib/mem.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/testcases/kernel/mem/lib/mem.c b/testcases/kernel/mem/lib/mem.c
> index 8fe4bf0..dc9d958 100644
> --- a/testcases/kernel/mem/lib/mem.c
> +++ b/testcases/kernel/mem/lib/mem.c
> @@ -39,8 +39,13 @@ static int alloc_mem(long int length, int testcase)
>  	if (s == MAP_FAILED)
>  		return errno;
>  
> -	if (testcase == MLOCK && mlock(s, length) == -1)
> -		return errno;
> +	if (testcase == MLOCK) {
> +		while (mlock(s, length) == -1) {
> +			if (EAGAIN != errno)
> +				return errno;
> +		}
> +	}
> +

Isn't this going to introduce infinite loop? Shouldn't we limit
the number of retries by some finite number before we let it
touch the pages (and hit OOM)?

Regards,
Jan

>  #ifdef HAVE_MADV_MERGEABLE
>  	if (testcase == KSM && madvise(s, length, MADV_MERGEABLE) == -1)
>  		return errno;
> --
> 1.8.3.1
> 
>