Re: [PATCH v2] printk: Use the main logbuf in NMI when logbuf_lock is available

From: Petr Mladek
Date: Fri May 19 2017 - 09:02:31 EST


On Fri 2017-05-19 13:38:15, Sergey Senozhatsky wrote:
> On (05/19/17 11:58), Sergey Senozhatsky wrote:
> > > void printk_nmi_exit(void)
> > > {
> > > - this_cpu_and(printk_context, ~PRINTK_NMI_CONTEXT_MASK);
> > > + this_cpu_and(printk_context,
> > > + ~(PRINTK_NMI_CONTEXT_MASK ||
> > > + PRINTK_NMI_DEFERRED_CONTEXT_MASK));
> > > }
>
> [..]
>
> > the problem is that
> >
> > `PRINTK_NMI_CONTEXT_MASK || PRINTK_NMI_DEFERRED_CONTEXT_MASK' is 0x01
>
> d'oh... forgot to copy-paste this...

Grrr, thanks a lot for chasing this down and I am sorry for the troubles.

> ---
>
> diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
> index 6fec9cfb9a69..b6ff3fe4370a 100644
> --- a/kernel/printk/printk_safe.c
> +++ b/kernel/printk/printk_safe.c
> @@ -324,7 +324,7 @@ void printk_nmi_enter(void)
> void printk_nmi_exit(void)
> {
> this_cpu_and(printk_context,
> - ~(PRINTK_NMI_CONTEXT_MASK ||
> + ~(PRINTK_NMI_CONTEXT_MASK |
> PRINTK_NMI_DEFERRED_CONTEXT_MASK));
> }

I have rebased both for-4.13 and for-next branches in printk.git
with this fix. I wanted to get rid of this bug in linux-next
ASAP. Please, let me know if you would prefer to handle
this another way in the future.

Best Regards,
Petr