On 07/11/2011 09:16 PM, Jan Kiszka wrote:
> On 2011-07-11 21:10, Jan Kiszka wrote:
>> On 2011-07-11 20:53, Gilles Chanteperdrix wrote:
>>> On 07/08/2011 06:29 PM, GIT version control wrote:
>>>> @@ -2528,6 +2534,22 @@ static inline void do_taskexit_event(struct 
>>>> task_struct *p)
>>>>    magic = xnthread_get_magic(thread);
>>>>    xnlock_get_irqsave(&nklock, s);
>>>> +
>>>> +  gksched = thread->gksched;
>>>> +  if (gksched) {
>>>> +          xnlock_put_irqrestore(&nklock, s);
>>> Are we sure irqs are on here? Are you sure that what is needed is not an
>>> xnlock_clear_irqon?
>> We are in the context of do_exit. Not only IRQs are on, also preemption.
>> And surely no nklock is held.
>>> Furthermore, I do not understand how we
>>> "synchronize" with the gatekeeper, how is the gatekeeper garanteed to
>>> wait for this assignment?
>> The gatekeeper holds the gksync token while it's active. We request it,
>> thus we wait for the gatekeeper to become idle again. While it is idle,
>> we reset the queued reference - but I just realized that this may tramp
>> on other tasks' values. I need to add a check that the value to be
>> null'ified is actually still ours.
> Thinking again, that's actually not a problem: gktarget is only needed
> while gksync is zero - but then we won't get hold of it anyway and,
> thus, can't cause any damage.

Well, you make it look like it does not work. From what I understand,
what you want is to set gktarget to null if a task being hardened is
destroyed. But by waiting for the semaphore, you actually wait for the
harden to be complete, so setting to NULL is useless. Or am I missing
something else?


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