Re: [Xenomai] Target frozen with rtcan_virt

[Thierry Bultel <thierry.bultel@wanadoo.fr>]

Hi Gilles,

Many thanks,
The first patch does not work, the second does.
I think the reason for 1st patch why is that in rtcan_virt, we have

rtdm_lock_get_irqsave(&rtcan_recv_list_lock, lock_ctx);
rtdm_lock_get(&rtcan_socket_lock);

...
--->        rtcan_rcv(rx_dev, &skb);
....

rtdm_lock_put(&rtcan_socket_lock);
rtdm_lock_put_irqrestore(&rtcan_recv_list_lock, lock_ctx);

and rtcan_rcv->rtcan_rcv_deliver->rtdm_sem_up(&sock->recv_sem);

thus the same re-scheduling stuff with interrupts locked.

Are you not not afraid of side effects with the second patch, 
since you change the overall behaviour ?
Won't you prefer a only locally modified rtcan_virt ?

eg something (not tested) like:

    xnpod_lock_sched()
    rtdm_lock_get_irqsave(&rtcan_recv_list_lock, lock_ctx);
    rtdm_lock_get(&rtcan_socket_lock);

...

                rtcan_rcv(rx_dev, &skb);

....

    rtdm_lock_put(&rtcan_socket_lock);
    rtdm_lock_put_irqrestore(&rtcan_recv_list_lock, lock_ctx);
    xnpod_unlock_sched()

Cheers
Thierry


Le 09/10/2012 23:51, Gilles Chanteperdrix a écrit :
> On 10/09/2012 11:41 PM, Gilles Chanteperdrix wrote:
>
>> Another possible fix would be to lock xenomai scheduler when taking an
>> rtdm_spin_lock, as it is almost always wrong to call xnpod_schedule in
>> such a situation. It works for other RT-CAN drivers, because they call
>> rtdm_sem_up from interrupt context where the scheduler is locked by the
>> XNINIRQ bit.
>>
>
> IOW, something like:
>
> diff --git a/include/rtdm/rtdm_driver.h b/include/rtdm/rtdm_driver.h
> index 68135e4..7b18c34 100644
> --- a/include/rtdm/rtdm_driver.h
> +++ b/include/rtdm/rtdm_driver.h
> @@ -730,6 +730,7 @@ typedef unsigned long rtdm_lockctx_t;
>  	do {							\
>  		XENO_BUGON(RTDM, !rthal_local_irq_disabled());	\
>  		rthal_spin_lock(lock);				\
> +		xnpod_lock_sched();				\
>  	} while (0)
>  #endif
>  
> @@ -749,7 +750,11 @@ typedef unsigned long rtdm_lockctx_t;
>   *
>   * Rescheduling: never.
>   */
> -#define rtdm_lock_put(lock)	rthal_spin_unlock(lock)
> +#define rtdm_lock_put(lock)					\
> +	do {							\
> +		rthal_spin_unlock(lock);			\
> +		xnpod_unlock_sched();				\
> +	} while (0)
>  
>  /**
>   * Acquire lock and disable preemption
> @@ -768,8 +773,11 @@ typedef unsigned long rtdm_lockctx_t;
>   *
>   * Rescheduling: never.
>   */
> -#define rtdm_lock_get_irqsave(lock, context)	\
> -	rthal_spin_lock_irqsave(lock, context)
> +#define rtdm_lock_get_irqsave(lock, context)				\
> +	do {								\
> +		rthal_spin_lock_irqsave(lock, context);			\
> +		xnpod_lock_sched();					\
> +	} while (0)
>  
>  /**
>   * Release lock and restore preemption state
> @@ -788,8 +796,12 @@ typedef unsigned long rtdm_lockctx_t;
>   *
>   * Rescheduling: possible.
>   */
> -#define rtdm_lock_put_irqrestore(lock, context)	\
> -	rthal_spin_unlock_irqrestore(lock, context)
> +#define rtdm_lock_put_irqrestore(lock, context)			\
> +	do {							\
> +		rthal_spin_unlock(lock);			\
> +		xnpod_unlock_sched();				\
> +		rthal_local_irq_restore(context);		\
> +	} while (0)
>  
>  /**
>   * Disable preemption locally
>
>
>