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Date: Mon, 12 Aug 2002 16:45:05 -0700 (PDT)
From: Linus Torvalds <torvalds@transmeta.com>
To: Andrew Morton <akpm@zip.com.au>
cc: Robert Love <rml@tech9.net>, Skip Ford <skip.ford@verizon.net>,
       "Adam J. Richter" <adam@yggdrasil.com>, <ryan.flanigan@intel.com>,
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Subject: Re: 2.5.31: modules don't work at all
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On Mon, 12 Aug 2002, Andrew Morton wrote:
> Linus Torvalds wrote:
> > 
> > On Mon, 12 Aug 2002, Andrew Morton wrote:
> > >
> > > Gets tricky with nested lock_kernels.
> > 
> > No, lock-kernel already only increments once, at the first lock_kernel. We
> > have a totally separate counter for the BKL depth, see <asm/smplock.h>
> > 
> 
> There are eighteen smplock.h's, all different.  At least one (SuperH)
> hasn't been converted to preempt.

Note that this should all be trivial, and in fact I think everybody shares 
the same smplock.h these days. The x86 smplock.h is 100% C - even though 
it's not actually totally visible because we still have some old asm 
routines visible that are just #ifdef'ed out.

In fact, I'll clean that up a bit to make it clearer.

> However, soldiering on leads us to some difficulties.  You're proposing,
> effectively, that preempt_count gets shifted left one bit and that bit
> zero becomes "has done lock_kernel()".

Actually, on slight introspection I suspect the better answer is to make
the BKL bit somewhere higher up, since BKL is much less interesting than
most spinlocks, and getting increasingly more so. But yes.

			Linus

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