On Mon, 2009-11-09 at 14:51 +0100, Jan Kiszka wrote: > Philippe Gerum wrote: > > On Mon, 2009-11-09 at 14:37 +0100, Philippe Gerum wrote: > >> On Mon, 2009-11-09 at 14:00 +0100, Jan Kiszka wrote: > >>> Hi Philippe, > >>> > >>> a customer just stumbled over some unclear spots in current I-pipe > >>> patches: > >>> > >>> Why is there local_irq_enable_hw in task_hijacked? Looks like it was > >>> once paired with prepare_arch_switch, but that call is now only used by > >>> legacy 2.4 PPC. > >> It is still used in all trees, since we define it in asm/ipipe.h. We > >> could not context switch properly on the linux side with hw interrupts > >> on anyway, due to the conflicts that would raise with Xenomai's tasking > >> code. > >> > >>> Can we safely drop it from all other patches (it's in > >>> the context switch fast-path...)? > >> No, since prepare_arch_switch() is still applicable. > >> > >>> Moreover, I bet the > >>> ENABLE_INTERRUPTS_HW_COND in entry_32.S' ret_from_fork is related to > >>> this as well, right? > >> No, it's there to prevent the scheduling tail from running hw IRQs off, > >> given that copy_thread() may set a copy for eflags which prevents > >> preemption. > > > > Forget about this one, this does not apply to x86 anymore. So the answer > > to this question is rather: that used to be required on x86 a long time > > ago due to the implementation of the task switching code in system.h > > (2.4 era IIRC); but in any case, yes, this is still required for the > > reasons explained above, since we must run the switch code with hw IRQs > > off. > > Still can't follow: Where is prepare_arch_switch referenced?
prepare_task_switch(), kernel/sched.c > My dumb > approach to do a text search over the ipipe patch and Xenomai failed to > find that spot. And then the question: How is disabling the IRQs that > task_hijacked reenables? > > Thanks, > Jan > -- Philippe. _______________________________________________ Adeos-main mailing list [email protected] https://mail.gna.org/listinfo/adeos-main
