On Wed, Nov 06, 2013 at 12:18:45PM +0100, Peter Zijlstra wrote:
> On Wed, Nov 06, 2013 at 10:31:31AM +0100, Peter Zijlstra wrote:
> > Subject: mm: Properly separate the bloated ptl from the regular case
> >
> > Use kernel/bounds.c to convert build-time spinlock_t size into a
> > preprocessor symbol and apply that to properly separate the page::ptl
> > situation.
> >
> > Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > ---
> > include/linux/mm.h | 24 +++++++++++++-----------
> > include/linux/mm_types.h | 9 +++++----
> > kernel/bounds.c | 2 ++
> > mm/memory.c | 11 +++++------
> > 4 files changed, 25 insertions(+), 21 deletions(-)
> >
> > diff --git a/kernel/bounds.c b/kernel/bounds.c
> > index e8ca97b5c386..5982437eca2c 100644
> > --- a/kernel/bounds.c
> > +++ b/kernel/bounds.c
> > @@ -11,6 +11,7 @@
> > #include <linux/kbuild.h>
> > #include <linux/page_cgroup.h>
> > #include <linux/log2.h>
> > +#include <linux/spinlock.h>
> >
> > void foo(void)
> > {
> > @@ -21,5 +22,6 @@ void foo(void)
> > #ifdef CONFIG_SMP
> > DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
> > #endif
> > + DEFINE(BLOATED_SPINLOCKS, sizeof(spinlock_t) > sizeof(int));
> > /* End of constants */
> > }
>
> Using that we could also do.. not been near a compiler.
>
[ Subject adjusted, CC: +Linus ]
> ---
> Subject: lockref: Use bloated_spinlocks to avoid explicit config dependencies
>
> Avoid the fragile Kconfig construct guestimating spinlock_t sizes; use a
> friendly compile-time test to determine this.
>
> Not-Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> ---
> lib/Kconfig | 3 ---
> lib/lockref.c | 2 +-
> 2 files changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/lib/Kconfig b/lib/Kconfig
> index b3c8be0da17f..254af289d1d0 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -54,9 +54,6 @@ config ARCH_USE_CMPXCHG_LOCKREF
> config CMPXCHG_LOCKREF
> def_bool y if ARCH_USE_CMPXCHG_LOCKREF
> depends on SMP
> - depends on !GENERIC_LOCKBREAK
> - depends on !DEBUG_SPINLOCK
> - depends on !DEBUG_LOCK_ALLOC
>
> config CRC_CCITT
> tristate "CRC-CCITT functions"
> diff --git a/lib/lockref.c b/lib/lockref.c
> index 6f9d434c1521..a158fd86aa1a 100644
> --- a/lib/lockref.c
> +++ b/lib/lockref.c
> @@ -1,7 +1,7 @@
> #include <linux/export.h>
> #include <linux/lockref.h>
>
> -#ifdef CONFIG_CMPXCHG_LOCKREF
> +#if defined(CONFIG_CMPXCHG_LOCKREF) && !BLOATED_SPINLOCKS
Having CONFIG_CMPXCHG_LOCKREF=y, but not really using it could be
misleading.
Should we get rid of CONFIG_CMPXCHG_LOCKREF completely and have here:
#if defined(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
defined(CONFIG_SMP) && !BLOATED_SPINLOCKS
?
--
Kirill A. Shutemov
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