Re: [Xenomai-help] Interrupt management under rtdm driver

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

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Jan Kiszka wrote:
> DOURNES Guillaume wrote:
>> Since I add the watchdog option in my kernel configuration, The software doesn't block.
>> But I obtain an EPREM (-1) error on the second call of rtdm_event_timedwait, and in dmesg : Xenomai: assertion failed at kernel/xenomai/skins/rtdm/drvlib.c:919 (!xnpod_unblockable_p()).
> 
> See, that is interesting.
> 
>> I don't understand why I have this error, because the rtdm_event_timedwait is used as the 16550A rtserial rtdm driver. And I use this rtserial driver, and it works.
>> Note that this problem doesn't appears when I call rt_task_suspend just after my rtdm_event_timedwait, and I resume the task by a gets.
> 
> After having a look at your driver source meanwhile, the problem is that
> you register your IOCTL handler also for handling invocation from non-RT
> (precisely: "secondary") context. But rtdm_event_timedwait always
> requires primary (RT) context. That is something you either have to
> check in the IOCTL handler before trying to block a caller - or you
> simply do not register for nrt_ioctl (or use a different handler for the
> set of IOCTLs in that context).
> 
> The reason that suspending the caller made this issue go away was that
> you have several plain Linux services in your RT loop that switches the
> caller automatically to secondary mode. Thus the first IOCTL succeeded,
> but the second failed after re-entering it now as a plain Linux caller.

...But suspending the thread shortly before IOCTL re-entry automatically
switch it back into the right (==RT) context.

Jan


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