On 2011-06-17 13:06, Gilles Chanteperdrix wrote: > On 06/17/2011 01:03 PM, Jan Kiszka wrote: >> On 2011-06-17 12:55, Gilles Chanteperdrix wrote: >>> On 06/17/2011 11:26 AM, Jan Kiszka wrote: >>>> Our current interrupt handlers assume that they leave over the same task >>>> and CPU they entered. But CONFIG_XENO_HW_UNLOCKED_SWITCH and commit >>>> f6af9b831c broke this assumption: xnpod_schedule invoked from the >>>> handler tail can now actually trigger a domain migration >>> >>> What unlocked context swith introduce from my point of view is simply >>> sections where interrupt happen which do not reschedule. >>> >>> f6af9b831c introduce a rescheduling point, but does not change what >>> happens during the interrupt handler either. >>> >>> So, I do not really understand this commit message. Either we can assume >>> that interrupt handlers migrate tasks or not, but this does not seem to >>> have anything to do with unlocked context switches or commit f6af9b831c. >> >> It has: Task is about to relax, re-enables interrupts in >> xnpod_resume_thread, IRQ hits, handler is entered over the relaxing RT >> task, xnpod_schedule in its tail performs the switch to root, which then >> continues to relaxed task, IRQ tail resumes over a different task, on >> SMP potentially also on a different CPU. I can send you a the trace if >> you want to have a closer look. > > Ok. Got it. But what has this to do with unlocked context switches ?
Also before commit f6af9b831c, there was a window with enabled IRQs in the relaxation path. So the above scenario should have been possible even earlier. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux _______________________________________________ Xenomai-core mailing list Xenomaiemail@example.com https://mail.gna.org/listinfo/xenomai-core