On Wed 2023-06-21 20:33:35, Tetsuo Handa wrote: > On 2023/06/21 19:40, Sebastian Andrzej Siewior wrote: > > printk_deferred_enter() has to be invoked in non-migrate-able context to > > ensure that deferred printing is enabled and disabled on the same CPU. > > I can't catch. local_irq_save(flags); makes non-migrate-able context > because sleeping is not allowed while IRQ is disabled, doesn't it? > > > This is the case after zonelist_update_seq has been acquired. > > > > Acquire zonelist_update_seq with write_seqlock_irqsave() and then defer > > printk output. > > What guarantees that write_seqlock_irqsave() never calls printk() > (e.g. lockdep warning) before printk_deferred_enter() takes effect? I think that we should explicitly disable preemption in printk_deferred_enter(). The disabled interrupts are not strictly necessary. I am going to resurrect the patch https://lore.kernel.org/r/20230419074210.17646-1-pmladek@xxxxxxxx and add the preempt_disable()/enable() at the same time. Is this going to work for you? Best Regards, Petr
