Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754543AbaBQUmv (ORCPT ); Mon, 17 Feb 2014 15:42:51 -0500 Received: from g1t0027.austin.hp.com ([15.216.28.34]:10913 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752086AbaBQUmH (ORCPT ); Mon, 17 Feb 2014 15:42:07 -0500 From: Waiman Long To: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Arnd Bergmann Cc: linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Steven Rostedt , Andrew Morton , Michel Lespinasse , Andi Kleen , Rik van Riel , "Paul E. McKenney" , Linus Torvalds , Raghavendra K T , George Spelvin , Tim Chen , Daniel J Blueman , Alexander Fyodorov , Aswin Chandramouleeswaran , Scott J Norton , Thavatchai Makphaibulchoke , Waiman Long Subject: [PATCH v4 2/3] qspinlock, x86: Enable x86-64 to use queue spinlock Date: Mon, 17 Feb 2014 15:41:23 -0500 Message-Id: <1392669684-4807-3-git-send-email-Waiman.Long@hp.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1392669684-4807-1-git-send-email-Waiman.Long@hp.com> References: <1392669684-4807-1-git-send-email-Waiman.Long@hp.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Acked-by: Rik van Riel --- arch/x86/Kconfig | 1 + arch/x86/include/asm/qspinlock.h | 55 +++++++++++++++++++++++++++++++++ arch/x86/include/asm/spinlock.h | 5 +++ arch/x86/include/asm/spinlock_types.h | 4 ++ 4 files changed, 65 insertions(+), 0 deletions(-) create mode 100644 arch/x86/include/asm/qspinlock.h diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 1b4ff87..5bf70ab 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..7316ec4 --- /dev/null +++ b/arch/x86/include/asm/qspinlock.h @@ -0,0 +1,55 @@ +#ifndef _ASM_X86_QSPINLOCK_H +#define _ASM_X86_QSPINLOCK_H + +#include + +#if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE) + +/* + * Queue spinlock union structure to be used within this header file only + */ +union qspinlock_x86 { + struct qspinlock slock; + u8 lock; /* Lock bit */ +}; + +#define queue_spin_trylock_unfair queue_spin_trylock_unfair +/** + * queue_spin_trylock_unfair - try to acquire the lock ignoring the qcode + * @lock: Pointer to queue spinlock structure + * Return: 1 if lock acquired, 0 if failed + */ +static __always_inline int queue_spin_trylock_unfair(struct qspinlock *lock) +{ + union qspinlock_x86 *qlock = (union qspinlock_x86 *)lock; + + if (!ACCESS_ONCE(qlock->lock) && + (cmpxchg(&qlock->lock, 0, _QSPINLOCK_LOCKED) == 0)) + return 1; + return 0; +} + +#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 qspinlock_x86 *qlock = (union qspinlock_x86 *)lock; + + barrier(); + ACCESS_ONCE(qlock->lock) = 0; + barrier(); +} + +#endif /* !CONFIG_X86_OOSTORE && !CONFIG_X86_PPRO_FENCE */ + +#include + +#endif /* _ASM_X86_QSPINLOCK_H */ diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index bf156de..6e6de1f 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -43,6 +43,10 @@ extern struct static_key paravirt_ticketlocks_enabled; static __always_inline bool static_key_false(struct static_key *key); +#ifdef CONFIG_QUEUE_SPINLOCK +#include +#else + #ifdef CONFIG_PARAVIRT_SPINLOCKS static inline void __ticket_enter_slowpath(arch_spinlock_t *lock) @@ -181,6 +185,7 @@ 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..98da00b 100644 --- a/arch/x86/include/asm/spinlock_types.h +++ b/arch/x86/include/asm/spinlock_types.h @@ -11,6 +11,9 @@ #define TICKET_SLOWPATH_FLAG ((__ticket_t)0) #endif +#ifdef CONFIG_QUEUE_SPINLOCK +#include +#else #if (CONFIG_NR_CPUS < (256 / __TICKET_LOCK_INC)) typedef u8 __ticket_t; typedef u16 __ticketpair_t; @@ -33,6 +36,7 @@ typedef struct arch_spinlock { } arch_spinlock_t; #define __ARCH_SPIN_LOCK_UNLOCKED { { 0 } } +#endif /* CONFIG_QUEUE_SPINLOCK */ #include -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/