Re: [RFC PATCH v1 10/25] printk: redirect emit/store to new ringbuffer

[Petr Mladek]

On Wed 2019-02-20 22:25:00, John Ogness wrote:
> On 2019-02-20, Petr Mladek <pmladek@xxxxxxxx> wrote:
> >> vprintk_emit and vprintk_store are the main functions that all printk
> >> variants eventually go through. Change these to store the message in
> >> the new printk ring buffer that the printk kthread is reading.
> >
> > Please, are there any candidates or plans to reuse the new ring
> > buffer implementation?
> 
> As you pointed out below, this patch already uses the ring buffer
> implementation for a totally different purpose: NMI safe dynamic memory
> allocation.

I have found an alternative solution. We could calculate the length
of the formatted string without any buffer:

	va_list args_copy;

	va_copy(args_copy, args);
	len = vscprintf(NULL, fmt, args_copy);
	va_end(args_copy);

This vsprintf() mode was implemented for exactly this purpose.

Best Regards,
Petr