Cc printk maintainers On Tue 03-09-19 17:42:28, Qian Cai wrote: > > > I suppose what happens is those skb_build() allocations are from softirq, > > > and > > > once one of them failed, it calls printk() which generates more interrupts. > > > Hence, the infinite loop. > > > > Please elaborate more. > > > > If you look at the original report, the failed allocation dump_stack() is, > > <IRQ> > warn_alloc.cold.43+0x8a/0x148 > __alloc_pages_nodemask+0x1a5c/0x1bb0 > alloc_pages_current+0x9c/0x110 > allocate_slab+0x34a/0x11f0 > new_slab+0x46/0x70 > ___slab_alloc+0x604/0x950 > __slab_alloc+0x12/0x20 > kmem_cache_alloc+0x32a/0x400 > __build_skb+0x23/0x60 > build_skb+0x1a/0xb0 > igb_clean_rx_irq+0xafc/0x1010 [igb] > igb_poll+0x4bb/0xe30 [igb] > net_rx_action+0x244/0x7a0 > __do_softirq+0x1a0/0x60a > irq_exit+0xb5/0xd0 > do_IRQ+0x81/0x170 > common_interrupt+0xf/0xf > </IRQ> > > Since it has no __GFP_NOWARN to begin with, it will call, > > printk > vprintk_default > vprintk_emit > wake_up_klogd > irq_work_queue > __irq_work_queue_local > arch_irq_work_raise > apic->send_IPI_self(IRQ_WORK_VECTOR) > smp_irq_work_interrupt > exiting_irq > irq_exit > > and end up processing pending net_rx_action softirqs again which are plenty due > to connected via ssh etc. -- Michal Hocko SUSE Labs
