Re: [RFC][PATCHv4 5/6] printk: use printk_safe buffers

[Sergey Senozhatsky]

On (11/25/16 15:28), Petr Mladek wrote:
[..]
> I really like this patch. The only small problem is that it enables
> lockdep and it does not explain why it is safe. The change itself
> looks fine but it took me some time to prove why. IMHO, it is
> worth a comment.
> 
> One thing is printk() recursion caused by lockdep warning
> triggered from inside vprintk_emit(). It is safe because
> the critical sections are guarded by printk_safe_enter()/exit()
> now.
> 
> Another thing is lockdep recursion caused by catching another lockdep
> issue when printing warning about the first one. This is safe
> because lockdep protects itself. First, it sets and checks
> current->lockdep_recursion around the critical sections.
> Second, further checks are disabled entirely once first
> lockdep issue is found.
> 
> If you add some comments about lockdep, feel free to use:

ok, I'll try to.

	-ss