Re: [LTP] [PATCH] Pipeio: Fix Error Use of Semctl(2)

[Subrata M. <su...@li...>]

On Thu, 2009-03-19 at 11:09 +0800, CAI Qian wrote:
> Hi,
> 
> The patch named
> 
>   [PATCH] aio and nonblocking io in tlibio.c and pipeio.c
>   http://article.gmane.org/gmane.linux.ltp/6643
> 
> unfortunately introduced a segmentation fault on PPC64.
> 
> # ./pipeio -T pipeio_1 -c 5 -s 4090 -i 100 -b -f x80
> Segmentation fault
> 
> This is due to the error use of semctl(2) pointed by Jakub Jelinek,
> 
>   The testcase is buggy. See man 3p semctl: The semctl() function
>   provides a variety of semaphore control operations as specified by
>   cmd. The fourth argument is optional and depends upon the operation
>   requested. If required, it is of type union semun, which the
>   application shall explicitly declare:
> 
>               union semun {
>                   int val;
>                   struct semid_ds *buf;
>                   unsigned short  *array;
>               } arg;
> 
>   If you fix the testcase up, particularly add:
>   union semun { int val; struct semid_ds *buf; unsigned short int
>   	      	*array;
>   };
>   and call
>   if(semctl(sem_id, 0, SETVAL, ((union semun) { .val = 0 })) == -1)
>   or
>   union u;
>   u.val = 0;
>   if(semctl(sem_id, 0, SETVAL, u) == -1)
>   it works just fine.
> 
> Signed-off-by: CAI Qian <ca...@cc...>

Thanks.

Regards--
Subrata

> 
> --- testcases/kernel/ipc/pipeio/pipeio.c.orig	2009-03-19 10:39:00.000000000 +0800
> +++ testcases/kernel/ipc/pipeio/pipeio.c	2009-03-19 10:42:45.000000000 +0800
> @@ -155,7 +155,13 @@
>  	char *toutput;		/* for getenv() */
>  	int sem_id;
>  	struct sembuf sem_op;
> -
> +	union semun {		/* for semctl() */
> +	  int val;
> +	  struct semid_ds *buf;
> +	  unsigned short int *array;
> +	} u;
> +	
> +	u.val = 0;
>  	format = HEX;
>  	blk_type = NON_BLOCKING_IO;
>  	dir[0] = '\0';
> @@ -443,7 +449,7 @@
>  		tst_brkm(TBROK, tst_exit, "Couldn't allocate semaphore: %s", strerror(errno));
>  	}
> 
> -	if(semctl(sem_id, 0, SETVAL, 0) == -1)
> +	if(semctl(sem_id, 0, SETVAL, u) == -1)
>  		tst_brkm(TBROK, tst_exit, "Couldn't initialize semaphore value: %s", strerror(errno));
> 
>  	if ( background ) {
> 
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