Re: [patch, -rc5-mm3] better lock debugging: remove mutex deadlock checking code

[Andy Whitcroft <apw@shadowen.org>]

Ingo Molnar wrote:
> * Randy.Dunlap <rdunlap@xenotime.net> wrote:
> 
> 
>>BUG: unable to handle kernel paging request at virtual address 22222232
> 
> 
> ok, this was a big thinko on my part, and it was right before our eyes. 
> Mutex deadlock checking relied on the 'big mutex debugging lock', but 
> that one is gone now - so mutex deadlock checking became racy (as your 
> crashes nicely pinpointed that). The races are more likely with an 
> increasing number of CPUs.
> 
> so the patch below finishes the cleanup i started: it removes deadlock 
> checking from the mutex code and lets the lock validator do that. This 
> should also be (much) faster on SMP, because the lock validator is 
> lockless in the fastpath. (if CONFIG_DEBUG_LOCKDEP is disabled)
> 
> 	Ingo
> 
> ----------------
> Subject: better lock debugging: remove mutex deadlock checking code
> From: Ingo Molnar <mingo@elte.hu>
> 
> with the lock validator we detect mutex deadlocks (and more), the mutex
> deadlock checking code is both redundant and slower. So remove it.
> 
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> ---

Ok, this patch in combination with either fix for the swap max bug are
showing passes across the board.

Acked-by: Andy Whitcroft <apw@shadowen.org>

-apw