[LTP] [PATCH] fcntl36: make sure write threads complete at least 1 loop

[Murphy Zhou]

On Fri, Feb 22, 2019 at 08:01:11PM +0100, Jan Stancek wrote:
> A failure has been reported while this test ran on a 1 CPU KVM guest
> with 4.20 kernel:
>   ...
>   fcntl36.c:303: INFO: OFD r/w lock vs POSIX read lock
>   fcntl36.c:360: FAIL: Unexpected data offset 3072 value 1
> 
> I wasn't able to reproduce it, to test the theory that
> one of write threads was given time on CPU only after
> loop_flag changed. Which means it wasn't able to complete
> a single iteration.

Ack. Thanks!

> 
> This patch makes sure that write threads make at least
> one iteration.
> 
> Signed-off-by: Jan Stancek <jstancek@redhat.com>
> ---
>  testcases/kernel/syscalls/fcntl/fcntl36.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/testcases/kernel/syscalls/fcntl/fcntl36.c b/testcases/kernel/syscalls/fcntl/fcntl36.c
> index 2942e4e6adc2..58a37e7bc562 100644
> --- a/testcases/kernel/syscalls/fcntl/fcntl36.c
> +++ b/testcases/kernel/syscalls/fcntl/fcntl36.c
> @@ -95,7 +95,7 @@ static void *fn_ofd_w(void *arg)
>  		.l_pid    = 0,
>  	};
>  
> -	while (loop_flag) {
> +	do {
>  
>  		memset(buf, wt, pa->length);
>  
> @@ -113,7 +113,7 @@ static void *fn_ofd_w(void *arg)
>  			wt = pa->cnt;
>  
>  		sched_yield();
> -	}
> +	} while (loop_flag);
>  
>  	pthread_barrier_wait(&barrier);
>  	SAFE_CLOSE(fd);
> @@ -134,7 +134,7 @@ static void *fn_posix_w(void *arg)
>  		.l_len    = pa->length,
>  	};
>  
> -	while (loop_flag) {
> +	do {
>  
>  		memset(buf, wt, pa->length);
>  
> @@ -152,7 +152,7 @@ static void *fn_posix_w(void *arg)
>  			wt = pa->cnt;
>  
>  		sched_yield();
> -	}
> +	} while (loop_flag);
>  
>  	pthread_barrier_wait(&barrier);
>  	SAFE_CLOSE(fd);
> -- 
> 1.8.3.1
>