Messages in this thread | | | Subject | Re: Spinlocks: Factor our GENERIC_LOCKBREAK in order to avoid spin with irqs disable | From | Peter Zijlstra <> | Date | Mon, 23 Jun 2008 19:54:13 +0200 |
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On Mon, 2008-06-23 at 19:19 +0200, Petr Tesarik wrote: > On Wed, 2008-05-07 at 11:49 -0700, Christoph Lameter wrote: > > Subject: Spinlocks: Factor our GENERIC_LOCKBREAK in order to avoid spin with irqs disabled > > > > The nice spinlock functions that enable interrupts while spinning are only > > usable if GENERIC_LOCKBREAK is set (and we do not debug locks but lock > > debugging would not be used for a production configuration). > > > > Factor out the dependencies on the ->lock_break field from the nice functions > > into a set of BREAKLOCK macros (cannot be functions since the type of the lock > > variable varies). > > > > The nice spinlock function can then also be used if !GENERIC_LOCKBREAK > > > > Signed-off-by: Christoph Lameter <clameter@sgi.com> > > > > --- > > kernel/spinlock.c | 40 ++++++++++++++++++++++++++++++---------- > > 1 file changed, 30 insertions(+), 10 deletions(-) > > > > Index: linux-2.6/kernel/spinlock.c > > =================================================================== > > --- linux-2.6.orig/kernel/spinlock.c 2008-05-07 11:19:31.000000000 -0700 > > +++ linux-2.6/kernel/spinlock.c 2008-05-07 11:40:56.000000000 -0700 > > @@ -65,7 +65,7 @@ EXPORT_SYMBOL(_write_trylock); > > * even on CONFIG_PREEMPT, because lockdep assumes that interrupts are > > * not re-enabled during lock-acquire (which the preempt-spin-ops do): > > */ > > -#if !defined(CONFIG_GENERIC_LOCKBREAK) || defined(CONFIG_DEBUG_LOCK_ALLOC) > > +#ifdef CONFIG_DEBUG_LOCK_ALLOC > > Maybe I'm just blind, but doesn't this change effectively disable any > arch-specific optimized code for _raw_*_lock? > > If CONFIG_DEBUG_LOCK_ALLOC is set, then CONFIG_DEBUG_SPINLOCK must also > be set, so in that case the debugging versions of _raw_*_lock are used. > But if CONFIG_DEBUG_LOCK_ALLOC is _not_ set, then the locks are built > with _trylock and _can_lock primitives. > > What am I missing here?
No, I think you're right.
I've been playing with these patches:
http://programming.kicks-ass.net/kernel-patches/spinlocks/
But as it stands it breaks !CONFIG_PREEMPT... ought to find some other cycles to spend on it..
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