Messages in this thread | | | Date | Fri, 11 May 2018 18:50:04 +0900 | From | Sergey Senozhatsky <> | Subject | Re: printk feature for syzbot? |
| |
On (05/11/18 11:17), Dmitry Vyukov wrote: > > From what I see, it seems that interrupts can be nested:
Hm, I thought that in general IRQ handlers run with local IRQs disabled on CPU. So, generally, IRQs don't nest. Was I wrong? NMIs can nest, that's true; but I thought that at least IRQs don't.
> https://syzkaller.appspot.com/bug?id=72eddef9cedcf81486adb9dd3e789f0d77505ba5 > https://syzkaller.appspot.com/bug?id=66fcf61c65f8aa50bbb862eb2fde27c08909a4ff > > Will this in_nmi()/in_irq()/in_serving_softirq()/else be enough to > untangle output printed by such nested interrupts?
Well, hm. __irq_enter() does preempt_count_add(HARDIRQ_OFFSET) and __irq_exit() does preempt_count_sub(HARDIRQ_OFFSET). So, technically, you can store
preempt_count() & HARDIRQ_MASK preempt_count() & SOFTIRQ_MASK preempt_count() & NMI_MASK
in that extended context tracking. The numbers will not tell you the IRQ line number, for instance, but at least you'll be able to distinguish different hard/soft IRQs, NMIs. Just an idea, I didn't check it, may be it won't work at all.
Ideally, the serial log should be like this
i:1 ... foo() i:1 ... bar() i:2 ... foo() // __irq_enter() i:2 ... bar() i:2 ... buz() // __irq_exit() i:1 ... buz()
but I may be completely wrong.
Petr and Steven probably will have better ideas.
-ss
| |