Re: [Xenomai-core] Pending ownership and resource stealing

[Jan Kiszka <jan.kiszka@domain.hid>]

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Philippe Gerum wrote:
> Jan Kiszka wrote:
> 
>> Besides this, we then may want to consider if introducing a pending
>> ownership of synch objects is worthwhile to improve efficiency of PIP
>> users. Not critical, but if it comes at a reasonable price... Will try
>> to draft something.
>>
> 
> I've committed an implementation of this stuff to the trunk, tested on
> your testcase over the simulator. So far, it's ok.

I'll give up, you are too fast for me. ;)

> The only thing that
> should change downstream compared to the previous behaviour is that
> xnsynch_sleep_on() might unblock immediately at skin level without any
> xnsynch_wakeup_sleeper() calls being previously invoked, since the
> blocking call does the stealing during the pending ownership window.
> 
> This means that skins now _must_ fix their internal state when unblocked
> from xnsynch_sleep_on() if they happen to track their own resource owner
> field for instance, since they might become the owner of such resource
> without any unlock/release/whatever routine being called at the said
> skin level. I've fixed a couple of skins for that purpose (not checked
> RTDM btw), but it would be safer if you could double-check the impact of
> such change on the interfaces you've crafted.

Well, if this means that once you have called xnsynch_wakeup_sleeper()
for some lower-prio task, you must call xnsynch_sleep_on() to steal it
for a higher-prio task, then RTDM needs fixing (it only sets a private
lock bit in this case).

> 
> This change only affects PIP-enabled synchronization objects in a
> reasonably limited manner and seems to behave properly, but please, give
> this code hell on your side too.
> 

Will do.

Jan


PS: The usage can be checked also via the cross reference:
http://www.rts.uni-hannover.de/xenomai/lxr/ident?v=SVN-trunk;i=XNSYNCH_PIP


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