Re: [Xenomai] [PATCH 1/1] rtdm: get spinlocks to lock the scheduler

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On 10/12/2012 08:51 AM, Gilles Chanteperdrix wrote:
> On 10/12/2012 08:26 AM, Gilles Chanteperdrix wrote:
> 
>> In a context where callbacks are called with spinlocks held, it is not
>> possible for drivers callbacks to wake up threads without holding any
>> spinlock. So, we need a mechanism to lock the scheduler when a spinlock
>> is grabbed. As xnpod_lock_sched/xnpod_unlock_sched may be a bit heavy
>> weight for this case, we try and reimplement a lighter version.
> 
> 
> There is a concurrence issue if, say, xnpod_suspend_thread or
> xnpod_reset_thread is called on another cpu while the thread which holds
> the scheduler lock is using an rtdm spinlock. I guess the rtdm spinlocks
> have to take the nklock to serialize access to the scheduler structures,
> so, use xnpod_lock_sched/xnpod_unlock_sched instead of
> __xnpod_lock_sched / __xnpod_unlock_sched.

Doesn't work either. So, handling the scheduler lock has to take place
in xnpod_schedule. What we can simply do is add a shortcut for this case
in __xnpod_schedule.

-- 
					    Gilles.