Philippe Gerum wrote: > 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
Ah, this is mainline! Thought is was an ipipe extension. OK, thanks, clear now: prepare_task_switch pairs with enabling in task_hijacked & ret_from_fork. Jan -- Siemens AG, Corporate Technology, CT SE 2 Corporate Competence Center Embedded Linux _______________________________________________ Adeos-main mailing list [email protected] https://mail.gna.org/listinfo/adeos-main
