Re: [Xenomai] Function to get state of lock variable

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2015-08-18 14:14, Wolfgang Netbal wrote:
> Hi All,
> 
> is there a function te returns true or false if a rtdm_lock_t variable
> is set ?
> What I have to do is  to check in an interrupt routine if the list is
> locked,
> if this is the case I leave the interrupt handler befor accessing the list.

Why? Why can't you simply spin until the lock is released - provided the
section that holds it is as short as in the code below?

Testing for a lock being held is usually only reasonable for debugging
purposes. trylock services make some sense in complex nested locking
scenarios or when creatively having to optimize the fast path. I dare to
say trying to use those mechanisms in a real-time context indicates that
the design has some other problem.

Jan

> 
> I use the following code to lock the add and replace of list elements.
> 
> static rtdm_lock_t opendev_list_lock;
> static int open(struct rtdm_dev_context *context, rtdm_user_info_t *
> user_info, int oflags)
> {
>     lrtdrv_context_t *ctx = (lrtdrv_context_t *) context->dev_private;
>     rtdm_lockctx_t s;
> 
> ....
> 
>     rtdm_lock_get_irqsave(&opendev_list_lock, s);
>     list_add_tail(&ctx->opendev_entry, &lrtdrv_opendev_list);
>     rtdm_lock_put_irqrestore(&opendev_list_lock, s);
> 
> 
>     return 0;
> }
> 
> Kind regards

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