Re: [RFC][PATCH 0/7] improve printk reliability

[Peter Zijlstra]

On Wed, 2011-12-21 at 11:57 +0100, Peter Zijlstra wrote:
> Hi,
> 
> So these are my current efforts to make my own console output more
> reliable. I've hit every deadlock described in this series and a few
> more.
> 
> With these patches applied I can printk() and WARN() from inside 
> scheduler context and not have my machine deadlock, even without the 
> aid of early_printk().
> 
> While I'll go an remove the sole printk() I found in the scheduler
> so that we don't have to rely on the console doing this, it is good
> to have a reliable console that can do this.
> 
> As it stands some of the patches, the semaphore one in particular,
> are really too ugly to live so I won't push those but wanted to share
> anyway.
> 
> Debugging this was 'fun', and I really hope to not have to do it
> again :-)

Also, these patches enable lockdep over printk(), allowing lockdep to
detect previously undetected deadlocks with console implementations,
irrespective of rq->lock.


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