Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756232Ab3JXUCm (ORCPT ); Thu, 24 Oct 2013 16:02:42 -0400 Received: from g1t0027.austin.hp.com ([15.216.28.34]:25618 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755201Ab3JXUCk (ORCPT ); Thu, 24 Oct 2013 16:02:40 -0400 From: Waiman Long To: Ingo Molnar , Andrew Morton , Thomas Gleixner Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Rik van Riel , Peter Hurley , Davidlohr Bueso , Alex Shi , Tim Chen , Linus Torvalds , Peter Zijlstra , Andrea Arcangeli , Matthew R Wilcox , Dave Hansen , Michel Lespinasse , Andi Kleen , Raghavendra K T , "Paul E. McKenney" , George Spelvin , "H. Peter Anvin" , Arnd Bergmann , Aswin Chandramouleeswaran , Scott J Norton , Davidlohr Bueso , Jason Low , Waiman Long Subject: [PATCH v8 10/10] MCS Lock: Make mcs_spinlock.h includable in other files Date: Thu, 24 Oct 2013 16:01:52 -0400 Message-Id: <1382644912-16458-1-git-send-email-Waiman.Long@hp.com> X-Mailer: git-send-email 1.7.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4358 Lines: 144 The following changes are made to enable mcs_spinlock.h file to be widely included in other files without causing problem: 1) Include a number of prerequisite header files and define arch_mutex_cpu_relax(), if not previously defined. 2) Separate out mcs_spin_lock() into a mcs_spinlock.c file. 3) Make mcs_spin_unlock() an inlined function. Signed-off-by: Waiman Long --- include/linux/mcs_spinlock.h | 43 ++++++++++++++++------------------------- kernel/Makefile | 6 ++-- kernel/mcs_spinlock.c | 37 ++++++++++++++++++++++++++++++++++++ 3 files changed, 57 insertions(+), 29 deletions(-) create mode 100644 kernel/mcs_spinlock.c diff --git a/include/linux/mcs_spinlock.h b/include/linux/mcs_spinlock.h index b5de3b0..62979f3 100644 --- a/include/linux/mcs_spinlock.h +++ b/include/linux/mcs_spinlock.h @@ -12,38 +12,29 @@ #ifndef __LINUX_MCS_SPINLOCK_H #define __LINUX_MCS_SPINLOCK_H +/* + * asm/processor.h may define arch_mutex_cpu_relax(). + * If it is not defined, cpu_relax() will be used. + */ +#include +#include +#include +#include + +#ifndef arch_mutex_cpu_relax +# define arch_mutex_cpu_relax() cpu_relax() +#endif + struct mcs_spinlock { struct mcs_spinlock *next; int locked; /* 1 if lock acquired */ }; -/* - * We don't inline mcs_spin_lock() so that perf can correctly account for the - * time spent in this lock function. - */ -static noinline -void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node) -{ - struct mcs_spinlock *prev; - - /* Init node */ - node->locked = 0; - node->next = NULL; - - prev = xchg(lock, node); - if (likely(prev == NULL)) { - /* Lock acquired */ - node->locked = 1; - return; - } - ACCESS_ONCE(prev->next) = node; - smp_wmb(); - /* Wait until the lock holder passes the lock down */ - while (!ACCESS_ONCE(node->locked)) - arch_mutex_cpu_relax(); -} +extern +void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node); -static void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node) +static inline +void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node) { struct mcs_spinlock *next = ACCESS_ONCE(node->next); diff --git a/kernel/Makefile b/kernel/Makefile index 1ce4755..2ad8454 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -50,9 +50,9 @@ obj-$(CONFIG_SMP) += smp.o ifneq ($(CONFIG_SMP),y) obj-y += up.o endif -obj-$(CONFIG_SMP) += spinlock.o -obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o -obj-$(CONFIG_PROVE_LOCKING) += spinlock.o +obj-$(CONFIG_SMP) += spinlock.o mcs_spinlock.o +obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o mcs_spinlock.o +obj-$(CONFIG_PROVE_LOCKING) += spinlock.o mcs_spinlock.o obj-$(CONFIG_UID16) += uid16.o obj-$(CONFIG_MODULES) += module.o obj-$(CONFIG_MODULE_SIG) += module_signing.o modsign_pubkey.o modsign_certificate.o diff --git a/kernel/mcs_spinlock.c b/kernel/mcs_spinlock.c new file mode 100644 index 0000000..6b20324 --- /dev/null +++ b/kernel/mcs_spinlock.c @@ -0,0 +1,37 @@ +/* + * MCS lock + * + * The MCS lock (proposed by Mellor-Crummey and Scott) is a simple spin-lock + * with the desirable properties of being fair, and with each cpu trying + * to acquire the lock spinning on a local variable. + * It avoids expensive cache bouncings that common test-and-set spin-lock + * implementations incur. + */ +#include +#include + +/* + * We don't inline mcs_spin_lock() so that perf can correctly account for the + * time spent in this lock function. + */ +void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node) +{ + struct mcs_spinlock *prev; + + /* Init node */ + node->locked = 0; + node->next = NULL; + + prev = xchg(lock, node); + if (likely(prev == NULL)) { + /* Lock acquired */ + node->locked = 1; + return; + } + ACCESS_ONCE(prev->next) = node; + smp_wmb(); + /* Wait until the lock holder passes the lock down */ + while (!ACCESS_ONCE(node->locked)) + arch_mutex_cpu_relax(); +} +EXPORT_SYMBOL(mcs_spin_lock); -- 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/