Re: [PATCH] printk: Add printk_flush() to force buffered text to console

[Joe Perches <joe@perches.com>]

On Thu, 2012-06-21 at 13:41 -0400, Steven Rostedt wrote:
> On Thu, 2012-06-21 at 10:13 -0700, Greg Kroah-Hartman wrote:
> 
> > > So mind re-sending the latest version of your printk flushing 
> > > fix? I'll apply it for v3.5-rc if other trees won't pick it up.
> > 
> > I'll be glad to pick it up, just make it work properly :)
> 
> I'm playing around with making a KERN_FLUSH "<f>". Think that's a better
> approach?

I don't think that's better.  I think it's worse
because it intermixes the idea of a kernel message
logging level with a specific functionality to
emit any fragmentary message immediately.

I think a global setting via a some functions like:

(printk private variable)
bool printk_buffered = true;

bool printk_set_buffering(bool enable)
{
	bool old_state = printk_buffered;
	printk_buffered = enable;

	return old_state;
}

and maybe:

bool printk_get_buffering(void)
{
	return printk_buffered;
}

would be better because the non-buffered use should
really be pretty isolated to last_breath type output
and to pretty isolated cases like your long running
tests.

A separate printk_flush() function if really necessary
but sprinking a bunch of printk_flush() calls seems
wasteful.