On Sun, Oct 25, 2020 at 8:12 AM Pingfan Liu <kernelfans@xxxxxxxxx> wrote: > > On Thu, Oct 22, 2020 at 4:37 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > > > > On Thu, Oct 22 2020 at 13:56, Pingfan Liu wrote: > > > I hit a irqflood bug on powerpc platform, and two years ago, on a x86 platform. > > > When the bug happens, the kernel is totally occupies by irq. Currently, there > > > may be nothing or just soft lockup warning showed in console. It is better > > > to warn users with irq flood info. > > > > > > In the kdump case, the kernel can move on by suppressing the irq flood. > > > > You're curing the symptom not the cause and the cure is just magic and > > can't work reliably. > Yeah, it is magic. But at least, it is better to printk something and > alarm users about what happens. With current code, it may show nothing > when system hangs. Thanks Pingfan and Thomas for the points - I'd like to have a mechanism in the kernel to warn users when an IRQ flood is potentially happening. Some time ago (2 years) we faced a similar issue in x86-64, a hard to debug problem in kdump, that eventually was narrowed to a buggy NIC FW flooding IRQs in kdump kernel, and no messages showed (although kernel changed a lot since that time, today we might have better IRQ handling/warning). We tried an early-boot fix, by disabling MSIs (as per PCI spec) early in x86 boot, but it wasn't accepted - Bjorn asked pertinent questions that I couldn't respond (I lost the reproducer) [0]. Cheers, Guilherme [0] lore.kernel.org/linux-pci/20181018183721.27467-1-gpiccoli@xxxxxxxxxxxxx _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
