On Fri, Nov 22, 2013 at 02:04:45PM -0500, Waiman Long wrote: > This patch makes the necessary changes at the x86 architecture specific > layer to enable the presence of the CONFIG_QUEUE_RWLOCK kernel option > to replace the read/write lock by the queue read/write lock. > > It also enables the CONFIG_QUEUE_RWLOCK option by default for x86 which > will force the use of queue read/write lock. That will greatly improve > the fairness of read/write lock and eliminate live-lock situation > where one task may not get the lock for an indefinite period of time. > > Signed-off-by: Waiman Long <[email protected]>
Reviewed-by: Paul E. McKenney <[email protected]> > --- > arch/x86/Kconfig | 1 + > arch/x86/include/asm/spinlock.h | 2 ++ > arch/x86/include/asm/spinlock_types.h | 4 ++++ > 3 files changed, 7 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index e903c71..c4a9c54 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -124,6 +124,7 @@ config X86 > select RTC_LIB > select HAVE_DEBUG_STACKOVERFLOW > select HAVE_IRQ_EXIT_ON_IRQ_STACK if X86_64 > + select QUEUE_RWLOCK > > config INSTRUCTION_DECODER > def_bool y > diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h > index bf156de..8fb88c5 100644 > --- a/arch/x86/include/asm/spinlock.h > +++ b/arch/x86/include/asm/spinlock.h > @@ -188,6 +188,7 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t > *lock) > cpu_relax(); > } > > +#ifndef CONFIG_QUEUE_RWLOCK > /* > * Read-write spinlocks, allowing multiple readers > * but only one writer. > @@ -270,6 +271,7 @@ static inline void arch_write_unlock(arch_rwlock_t *rw) > asm volatile(LOCK_PREFIX WRITE_LOCK_ADD(%1) "%0" > : "+m" (rw->write) : "i" (RW_LOCK_BIAS) : "memory"); > } > +#endif /* CONFIG_QUEUE_RWLOCK */ > > #define arch_read_lock_flags(lock, flags) arch_read_lock(lock) > #define arch_write_lock_flags(lock, flags) arch_write_lock(lock) > diff --git a/arch/x86/include/asm/spinlock_types.h > b/arch/x86/include/asm/spinlock_types.h > index 4f1bea1..a585635 100644 > --- a/arch/x86/include/asm/spinlock_types.h > +++ b/arch/x86/include/asm/spinlock_types.h > @@ -34,6 +34,10 @@ typedef struct arch_spinlock { > > #define __ARCH_SPIN_LOCK_UNLOCKED { { 0 } } > > +#ifdef CONFIG_QUEUE_RWLOCK > +#include <asm-generic/qrwlock.h> > +#else > #include <asm/rwlock.h> > +#endif > > #endif /* _ASM_X86_SPINLOCK_TYPES_H */ > -- > 1.7.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
