Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755729Ab3IYWKz (ORCPT ); Wed, 25 Sep 2013 18:10:55 -0400 Received: from mga02.intel.com ([134.134.136.20]:5797 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754860Ab3IYWKx (ORCPT ); Wed, 25 Sep 2013 18:10:53 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.90,981,1371106800"; d="scan'208";a="409401462" Subject: [PATCH v6 5/6] MCS Lock: Restructure the MCS lock defines and locking code into its own file From: Tim Chen To: Ingo Molnar , Andrew Morton Cc: Andrea Arcangeli , Alex Shi , Andi Kleen , Michel Lespinasse , Davidlohr Bueso , Matthew R Wilcox , Dave Hansen , Peter Zijlstra , Rik van Riel , Peter Hurley , Tim Chen , linux-kernel@vger.kernel.org, linux-mm In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Date: Wed, 25 Sep 2013 15:10:49 -0700 Message-ID: <1380147049.3467.67.camel@schen9-DESK> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 (2.32.3-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5301 Lines: 190 We will need the MCS lock code for doing optimistic spinning for rwsem. Extracting the MCS code from mutex.c and put into its own file allow us to reuse this code easily for rwsem. Signed-off-by: Tim Chen Signed-off-by: Davidlohr Bueso --- include/linux/mcslock.h | 58 +++++++++++++++++++++++++++++++++++++++++++++++ kernel/mutex.c | 58 +++++----------------------------------------- 2 files changed, 65 insertions(+), 51 deletions(-) create mode 100644 include/linux/mcslock.h diff --git a/include/linux/mcslock.h b/include/linux/mcslock.h new file mode 100644 index 0000000..20fd3f0 --- /dev/null +++ b/include/linux/mcslock.h @@ -0,0 +1,58 @@ +/* + * MCS lock defines + * + * This file contains the main data structure and API definitions of MCS lock. + */ +#ifndef __LINUX_MCSLOCK_H +#define __LINUX_MCSLOCK_H + +struct mcs_spin_node { + struct mcs_spin_node *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_spin_node **lock, struct mcs_spin_node *node) +{ + struct mcs_spin_node *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(); +} + +static void mcs_spin_unlock(struct mcs_spin_node **lock, struct mcs_spin_node *node) +{ + struct mcs_spin_node *next = ACCESS_ONCE(node->next); + + if (likely(!next)) { + /* + * Release the lock by setting it to NULL + */ + if (cmpxchg(lock, node, NULL) == node) + return; + /* Wait until the next pointer is set */ + while (!(next = ACCESS_ONCE(node->next))) + arch_mutex_cpu_relax(); + } + ACCESS_ONCE(next->locked) = 1; + smp_wmb(); +} + +#endif diff --git a/kernel/mutex.c b/kernel/mutex.c index 6d647ae..1b6ba3f 100644 --- a/kernel/mutex.c +++ b/kernel/mutex.c @@ -25,6 +25,7 @@ #include #include #include +#include /* * In the DEBUG case we are using the "NULL fastpath" for mutexes, @@ -111,54 +112,9 @@ EXPORT_SYMBOL(mutex_lock); * more or less simultaneously, the spinners need to acquire a MCS lock * first before spinning on the owner field. * - * We don't inline mspin_lock() so that perf can correctly account for the - * time spent in this lock function. */ -struct mspin_node { - struct mspin_node *next ; - int locked; /* 1 if lock acquired */ -}; -#define MLOCK(mutex) ((struct mspin_node **)&((mutex)->spin_mlock)) -static noinline -void mspin_lock(struct mspin_node **lock, struct mspin_node *node) -{ - struct mspin_node *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(); -} - -static void mspin_unlock(struct mspin_node **lock, struct mspin_node *node) -{ - struct mspin_node *next = ACCESS_ONCE(node->next); - - if (likely(!next)) { - /* - * Release the lock by setting it to NULL - */ - if (cmpxchg(lock, node, NULL) == node) - return; - /* Wait until the next pointer is set */ - while (!(next = ACCESS_ONCE(node->next))) - arch_mutex_cpu_relax(); - } - ACCESS_ONCE(next->locked) = 1; - smp_wmb(); -} +#define MLOCK(mutex) ((struct mcs_spin_node **)&((mutex)->spin_mlock)) /* * Mutex spinning code migrated from kernel/sched/core.c @@ -448,7 +404,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, for (;;) { struct task_struct *owner; - struct mspin_node node; + struct mcs_spin_node node; if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) { struct ww_mutex *ww; @@ -470,10 +426,10 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, * If there's an owner, wait for it to either * release the lock or go to sleep. */ - mspin_lock(MLOCK(lock), &node); + mcs_spin_lock(MLOCK(lock), &node); owner = ACCESS_ONCE(lock->owner); if (owner && !mutex_spin_on_owner(lock, owner)) { - mspin_unlock(MLOCK(lock), &node); + mcs_spin_unlock(MLOCK(lock), &node); goto slowpath; } @@ -488,11 +444,11 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, } mutex_set_owner(lock); - mspin_unlock(MLOCK(lock), &node); + mcs_spin_unlock(MLOCK(lock), &node); preempt_enable(); return 0; } - mspin_unlock(MLOCK(lock), &node); + mcs_spin_unlock(MLOCK(lock), &node); /* * When there's no owner, we might have preempted between the -- 1.7.4.4 -- 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/