Re: patch for common networking error messages

[Andrew Morton <akpm@xxxxxxxxx>]

Andi Kleen <ak@xxxxxxx> wrote:
>
> > Actually it already does, to cover the case where an interrupt handler calls
> > printk while process-context code is performing a printk.
> 
> I don't think it'll work. Both printk and release_console_sem take the 
> logbuf_lock,
> which will deadlock if the same CPU already holds it.

Look more closely.

logbuf_lock is only held to protect the logbuf contents and its indices. 
And to pin down the current console_sem holder to reliably ensure that
he'll print the text which the nested printer just placed in the buffer.

We do not call the console drivers while holding logbuf_lock.  console_sem
is held across the console driver call.