Re: [PATCH -rt] printk: Don't emit console_cpu_notify() for CPU_DYING

[Yong Zhang <yong.zhang0@gmail.com>]

On Wed, Nov 16, 2011 at 03:48:11PM +0100, Thomas Gleixner wrote:
> On Wed, 16 Nov 2011, Steven Rostedt wrote:
> > Thomas, doesn't printk not print to serial in atomic contexts? Or did

I guess you mean console_trylock_for_printk() will fail in atomic context?
If so, yeah, that doesn't change.

But the issue is console_cpu_notify() call console_lock() directly.
That means below scenario could also happen in mainline:

	CPU A				CPU B

doing printk with console_sem held
				take_cpu_down();
				  cpu_notify(CPU_DYING);
				    console_cpu_notify();
				      console_lock();
				        down(&console_sem);
					  *bang*
  up(&console_sem);

Sounds I should also send this patch to mainline.

Thanks,
Yong