linux-kernel - Re: [rfc] lock bitops

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Message-ID: <20070508224548.GE20174@wotan.suse.de>
Date:	Wed, 9 May 2007 00:45:48 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Matthew Wilcox <matthew@....cx>
Cc:	linux-arch@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [rfc] lock bitops

On Tue, May 08, 2007 at 04:40:36PM -0600, Matthew Wilcox wrote:
> On Wed, May 09, 2007 at 12:29:27AM +0200, Nick Piggin wrote:
> > On Tue, May 08, 2007 at 09:06:32AM -0600, Matthew Wilcox wrote:
> > > On Tue, May 08, 2007 at 01:37:09PM +0200, Nick Piggin wrote:
> > > > --
> > > > Introduce test_and_set_bit_lock / clear_bit_unlock bitops with lock semantics.
> > > > Add non-trivial for powerpc and ia64. Convert page lock, buffer lock,
> > > > bit_spin_lock, tasklet locks to use the new locks.
> > > 
> > > The names are a bit clumsy.  How about naming them after the effect,
> > > rather than the implementation?  It struck me that really these things
> > > are bit mutexes -- you can sleep while holding the lock.  How about
> > > calling them bit_mutex_trylock() and bit_mutex_unlock()?
> > 
> > bit_spin_trylock / bit_spin_unlock be OK? ;)
> 
> We already have a bit_spin_trylock -- it keeps preempt disabled until
> you bit_spin_unlock.  Oh, and it only actually sets a bit if you've got
> SMP or lock debugging on.  Nice try though ;-)

OK, I'll be blunt then. I think s/test_and_set_bit_lock/bit_mutex_trylock
is much worse ;)
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