[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v8 02/10] qspinlock, x86: Enable x86-64 to use queue spinlock
This patch makes the necessary changes at the x86 architecture specific layer to enable the use of queue spinlock for x86-64. As x86-32 machines are typically not multi-socket. The benefit of queue spinlock may not be apparent. So queue spinlock is not enabled. Currently, there is some incompatibilities between the para-virtualized spinlock code (which hard-codes the use of ticket spinlock) and the queue spinlock. Therefore, the use of queue spinlock is disabled when the para-virtualized spinlock is enabled. The arch/x86/include/asm/qspinlock.h header file includes some x86 specific optimization which will make the queue spinlock code perform better than the generic implementation. Signed-off-by: Waiman Long <Waiman.Long@xxxxxx> Acked-by: Rik van Riel <riel@xxxxxxxxxx> --- arch/x86/Kconfig | 1 + arch/x86/include/asm/qspinlock.h | 41 +++++++++++++++++++++++++++++++++ arch/x86/include/asm/spinlock.h | 5 ++++ arch/x86/include/asm/spinlock_types.h | 4 +++ 4 files changed, 51 insertions(+), 0 deletions(-) create mode 100644 arch/x86/include/asm/qspinlock.h diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 0af5250..de573f9 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -17,6 +17,7 @@ config X86_64 depends on 64BIT select X86_DEV_DMA_OPS select ARCH_USE_CMPXCHG_LOCKREF + select ARCH_USE_QUEUE_SPINLOCK ### Arch settings config X86 diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h new file mode 100644 index 0000000..44cefee --- /dev/null +++ b/arch/x86/include/asm/qspinlock.h @@ -0,0 +1,41 @@ +#ifndef _ASM_X86_QSPINLOCK_H +#define _ASM_X86_QSPINLOCK_H + +#include <asm-generic/qspinlock_types.h> + +#if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE) + +#define _ARCH_SUPPORTS_ATOMIC_8_16_BITS_OPS + +/* + * x86-64 specific queue spinlock union structure + */ +union arch_qspinlock { + struct qspinlock slock; + u8 lock; /* Lock bit */ +}; + +#define queue_spin_unlock queue_spin_unlock +/** + * queue_spin_unlock - release a queue spinlock + * @lock : Pointer to queue spinlock structure + * + * No special memory barrier other than a compiler one is needed for the + * x86 architecture. A compiler barrier is added at the end to make sure + * that the clearing the lock bit is done ASAP without artificial delay + * due to compiler optimization. + */ +static inline void queue_spin_unlock(struct qspinlock *lock) +{ + union arch_qspinlock *qlock = (union arch_qspinlock *)lock; + + barrier(); + ACCESS_ONCE(qlock->lock) = 0; + barrier(); +} + +#endif /* !CONFIG_X86_OOSTORE && !CONFIG_X86_PPRO_FENCE */ + +#include <asm-generic/qspinlock.h> + +#endif /* _ASM_X86_QSPINLOCK_H */ diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index 0f62f54..958d20f 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -42,6 +42,10 @@ extern struct static_key paravirt_ticketlocks_enabled; static __always_inline bool static_key_false(struct static_key *key); +#ifdef CONFIG_QUEUE_SPINLOCK +#include <asm/qspinlock.h> +#else + #ifdef CONFIG_PARAVIRT_SPINLOCKS static inline void __ticket_enter_slowpath(arch_spinlock_t *lock) @@ -180,6 +184,7 @@ static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock, { arch_spin_lock(lock); } +#endif /* CONFIG_QUEUE_SPINLOCK */ static inline void arch_spin_unlock_wait(arch_spinlock_t *lock) { diff --git a/arch/x86/include/asm/spinlock_types.h b/arch/x86/include/asm/spinlock_types.h index 4f1bea1..7960268 100644 --- a/arch/x86/include/asm/spinlock_types.h +++ b/arch/x86/include/asm/spinlock_types.h @@ -23,6 +23,9 @@ typedef u32 __ticketpair_t; #define TICKET_SHIFT (sizeof(__ticket_t) * 8) +#ifdef CONFIG_QUEUE_SPINLOCK +#include <asm-generic/qspinlock_types.h> +#else typedef struct arch_spinlock { union { __ticketpair_t head_tail; @@ -33,6 +36,7 @@ typedef struct arch_spinlock { } arch_spinlock_t; #define __ARCH_SPIN_LOCK_UNLOCKED { { 0 } } +#endif /* CONFIG_QUEUE_SPINLOCK */ #include <asm/rwlock.h> -- 1.7.1 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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