Re: Planning for NetBSD 5.0

[Michael Lorenz <macallan%NetBSD.org@localhost>]

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Hello,

On May 6, 2008, at 08:33, Izumi Tsutsui wrote:
> -current kernel with DIAGNOSTIC + DEBUG gets the following assert:
>
> ---
> panic: kernel diagnostic assertion "evt != 0" failed: \
> file "../../../../arch/macppc/macppc/pic_ohare.c", line 272
> Stopped in pid 13155.1 (cc1) at netbsd:cpu_Debugger+0x10:       \
> lwz     r0, r1, 0x14
> db> tr
> 0x008f2ed0: at panic+0x210
> 0x008f2f20: at __kernassert+0x4c
> 0x008f2f30: at ohare_get_irq+0x160
> 0x008f2f50: at pic_handle_intr+0x5c
> 0x008f2fa0: at trapstart+0x8fc
> 0xffffcb70: at _prop_dictionary_keysym32_pool+0x4b71f098
> ---
>
> Any clue?

Yes, it's the ohare PIC handler. Please build a kernel with options  
OHARE_DEBUG and try again. What happened is that ohare_get_irq() had  
more than one interrupt pending, tried to return them according to  
priority but ended up with nothing - it ORs up all the priorities of  
all the pending interrupts, then looks for pending interrupts at the  
highest found priority and didn't find anything. Your machine must  
have triggered some corner case that doesn't happen on my PowerBook.
That said, I'm not sure the interrupt ordering stuff is worth the  
trouble anyway.
Hmm, mask shouldn't be an int, it should be uint32_t but that  
shouldn't matter, we don't do anything with it where the sign bit  
could do anything funny.
And the code screws up if you ever disestablish an interrupt -  
ohare_establish_irq() should always re-calculate all bitmasks to be  
safe. Actually that would cause exactly the problem you're seeing.

Please try this pseudo-patch too, it should bypass the priority code  
and simply return interrupts from left to right:
        /*
         * if we get here we have more than one irq pending so return them
         * according to priority
         */
        evt = ohare->pending_events & ~mask;
+#if 0
        prio = ohare->irqs[bit];
        while (evt != 0) {
                bit = 31 - cntlzw(evt);
                prio |= ohare->irqs[bit];
                evt &= ~(1 << bit);
#ifdef OHARE_DEBUG
                bail++;
                if (bail > 31)
                        panic("hanging in ohare_get_irq");
#endif
        }
        lvl = 31 - cntlzw(prio);
        evt = ohare->pending_events & ohare->irqs[lvl];
#ifdef OHARE_DEBUG
        if (evt == 0) {
                printf("ohare interrupt fuckup\n");
                printf("pending: %08x\n", ohare->pending_events);
                /* should bitch a bit more here */
        }
#else
        KASSERT(evt != 0);
#endif
+#endif /* bypass priority stuff */
        bit = 31 - cntlzw(evt);
        mask = 1 << bit;
        ohare->pending_events &= ~mask;
        return bit;     

have fun
Michael

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