[LTP] [PATCH 1/2] ltp-aiodio: sleep less time when waiting for target file creation

[Cyril Hrubis]

Hi!
> dio_sparse calls read_sparse() to check the content of sparse file,
> which is direct written by another process. It waits for the file to be
> existent in a loop and sleeps 0.1s in each loop if the file isn't there
> yet.
> 
> But the sleep time is too long, if the target file doesn't exist in the
> first loop, the reading process might never read the file before it gets
> killed. e.g. Running ADSP045 on extN I got:
> 
> dio_sparse    0  TINFO  :  Dirtying free blocks
> dio_sparse    0  TINFO  :  Starting I/O tests
> Child 4554 waits for 'dio_sparse' to appear
> dio_sparse    0  TINFO  :  Killing childrens(s)
> dio_sparse    1  TPASS  :  Test passed)
> 
> The child for reading got killed before it read anything.
> 
> So shorten the sleep time, give the child a chance to read the file and
> really do the test.
> 
> dio_sparse    0  TINFO  :  Dirtying free blocks
> dio_sparse    0  TINFO  :  Starting I/O tests
> Child 4767 waits for 'dio_sparse' to appear
> Child 4767 has opened 'dio_sparse' for reading
> Child 4767 loop 0
> Child 4767 loop 1
> dio_sparse    0  TINFO  :  Killing childrens(s)
> dio_sparse    1  TPASS  :  Test passed)
> 
> Signed-off-by: Eryu Guan <eguan@redhat.com>
> ---
>  testcases/kernel/io/ltp-aiodio/common_sparse.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/testcases/kernel/io/ltp-aiodio/common_sparse.h b/testcases/kernel/io/ltp-aiodio/common_sparse.h
> index f7f4ef4..a7f5035 100644
> --- a/testcases/kernel/io/ltp-aiodio/common_sparse.h
> +++ b/testcases/kernel/io/ltp-aiodio/common_sparse.h
> @@ -123,7 +123,7 @@ static void read_sparse(char *filename, int filesize)
>  			fprintf(stderr, "Child %i waits for '%s' to appear\n",
>  			        getpid(), filename);
>  
> -		usleep(100000);
> +		usleep(10);

This is just another band aid instead of fixing the real problem. Why
don't we use real synchronization instead?

What about we do:

* Remove the loops that kills children from the parent
* Limit the number of iterations in read_sparse to something
  more reasonable, i.e. 10 or so

That way the parent would actually wait for the children to read the
file in the loop that does wait().

-- 
Cyril Hrubis
chrubis@suse.cz