Re: [Xenomai-core] [Xenomai-git] Jan Kiszka : nucleus: Fix interrupt handler tails

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

On 2011-06-17 18:53, Gilles Chanteperdrix wrote:
> On 06/17/2011 04:38 PM, GIT version control wrote:
>> Module: xenomai-jki
>> Branch: for-upstream
>> Commit: 7203b1a66ca0825d5bcda1c3abab9ca048177914
>> URL:    http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=7203b1a66ca0825d5bcda1c3abab9ca048177914
>>
>> Author: Jan Kiszka <jan.kiszka@domain.hid>
>> Date:   Fri Jun 17 09:46:19 2011 +0200
>>
>> nucleus: Fix interrupt handler tails
>>
>> Our current interrupt handlers assume that they leave over the same task
>> and CPU they entered. But commit f6af9b831c broke this assumption:
>> xnpod_schedule invoked from the handler tail can now actually trigger a
>> domain migration, and that can also include a CPU migration. This causes
>> subtle corruptions as invalid xnstat_exectime_t objects may be restored
>> and - even worse - we may improperly flush XNHTICK of the old CPU,
>> leaving Linux timer-wise dead there (as happened to us).
>>
>> Fix this by moving XNHTICK replay and exectime accounting before the
>> scheduling point. Note that this introduces a tiny imprecision in the
>> accounting.
> 
> I am not sure I understand why moving the XNHTICK replay is needed: if
> we switch to secondary mode, the HTICK is handled by xnpod_schedule
> anyway, or am I missing something?

The replay can work on an invalid sched (after CPU migration in
secondary mode). We could reload the sched, but just moving the replay
is simpler.

Jan

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