Re: [PATCH v4 2/5] printk/nmi: use IRQ work only when ready

Sergey Senozhatsky
2016-04-04T04:55:16Z

Hello,

On (03/30/16 17:53), Petr Mladek wrote:
> NMIs could happen at any time. This patch makes sure that the safe
> printk() in NMI will schedule IRQ work only when the related structs are
> initialized.
>
> All pending messages are flushed when the IRQ work is being initialized.

so, does this patch 'fix' 0001 (in a way)? shouldn't it then be folded?
sorry if I'm missing something.

-ss

> DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
> +static int printk_nmi_irq_ready;
>
> #define NMI_LOG_BUF_LEN (4096 - sizeof(atomic_t) - sizeof(struct irq_work))
>
> @@ -84,8 +85,11 @@ again:
> goto again;
>
> /* Get flushed in a more safe context. */
> - if (add)
> + if (add && printk_nmi_irq_ready) {
> + /* Make sure that IRQ work is really initialized. */
> + smp_rmb();
> irq_work_queue(&s->work);
> + }
>
> return add;
> }
> @@ -195,6 +199,13 @@ void __init printk_nmi_init(void)
>
> init_irq_work(&s->work, __printk_nmi_flush);
> }
> +
> + /* Make sure that IRQ works are initialized before enabling. */
> + smp_wmb();
> + printk_nmi_irq_ready = 1;
> +
> + /* Flush pending messages that did not have scheduled IRQ works. */
> + printk_nmi_flush();
> }