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SubjectRe: [PATCH 4/7] ufs: remove the BKL
On 2011-03-02 00:13 +0100, Arnd Bergmann wrote:
> This introduces a new per-superblock mutex in UFS to replace
> the big kernel lock. I have been careful to avoid nested
> calls to lock_ufs and to get the lock order right with
> respect to other mutexes, in particular lock_super.
>
> I did not make any attempt to prove that the big kernel
> lock is not needed in a particular place in the code,
> which is very possible.
>
> The code is still only compile-tested,

This isn't true anymore; I've been running with this patch (well, the
previous versions thereof) for some time now. On the other hand, I
don't use all of this driver's features.

> but it should at least be harmless on non-SMP systems, since the new
> mutex is not taken on those.

I think this part of the patch is strange. It seems like a gratuitous
difference between SMP/preempt and other systems to #if out the code
that takes the mutex. This might make problems with the conversion fly
under the radar longer because people with older systems won't encounter
them.
--
Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/)


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