From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f49.google.com (mail-pa0-f49.google.com [209.85.220.49]) by kanga.kvack.org (Postfix) with ESMTP id 035166B00B7 for ; Tue, 21 Jan 2014 18:36:14 -0500 (EST) Received: by mail-pa0-f49.google.com with SMTP id hz1so9056188pad.22 for ; Tue, 21 Jan 2014 15:36:14 -0800 (PST) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTP id l8si7292700pao.65.2014.01.21.15.36.13 for ; Tue, 21 Jan 2014 15:36:13 -0800 (PST) Subject: [PATCH v9 4/6] MCS Lock: Allow architectures to hook in to contended paths From: Tim Chen In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Date: Tue, 21 Jan 2014 15:36:10 -0800 Message-ID: <1390347370.3138.65.camel@schen9-DESK> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar , Andrew Morton , Thomas Gleixner , "Paul E.McKenney" , Will Deacon Cc: linux-kernel@vger.kernel.org, linux-mm , linux-arch@vger.kernel.org, Linus Torvalds , Waiman Long , Andrea Arcangeli , Alex Shi , Andi Kleen , Michel Lespinasse , Davidlohr Bueso , Matthew R Wilcox , Dave Hansen , Peter Zijlstra , Rik van Riel , Peter Hurley , Tim Chen , Raghavendra K T , George Spelvin , "H. Peter Anvin" , Arnd Bergmann , Aswin Chandramouleeswaran , Scott J Norton , "Figo.zhang" From: Will Deacon Signed-off-by: Will Deacon Signed-off-by: Tim Chen --- include/linux/mcs_spinlock.h | 42 ++++++++++++++++++++++++++++-------------- 1 file changed, 28 insertions(+), 14 deletions(-) diff --git a/include/linux/mcs_spinlock.h b/include/linux/mcs_spinlock.h index 143fa42..e9a4d74 100644 --- a/include/linux/mcs_spinlock.h +++ b/include/linux/mcs_spinlock.h @@ -17,6 +17,28 @@ struct mcs_spinlock { int locked; /* 1 if lock acquired */ }; +#ifndef arch_mcs_spin_lock_contended +/* + * Using smp_load_acquire() provides a memory barrier that ensures + * subsequent operations happen after the lock is acquired. + */ +#define arch_mcs_spin_lock_contended(l) \ +do { \ + while (!(smp_load_acquire(l))) \ + arch_mutex_cpu_relax(); \ +} while (0) +#endif + +#ifndef arch_mcs_spin_unlock_contended +/* + * smp_store_release() provides a memory barrier to ensure all + * operations in the critical section has been completed before + * unlocking. + */ +#define arch_mcs_spin_unlock_contended(l) \ + smp_store_release((l), 1) +#endif + /* * Note: the smp_load_acquire/smp_store_release pair is not * sufficient to form a full memory barrier across @@ -58,13 +80,9 @@ void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node) return; } ACCESS_ONCE(prev->next) = node; - /* - * Wait until the lock holder passes the lock down. - * Using smp_load_acquire() provides a memory barrier that - * ensures subsequent operations happen after the lock is acquired. - */ - while (!(smp_load_acquire(&node->locked))) - arch_mutex_cpu_relax(); + + /* Wait until the lock holder passes the lock down. */ + arch_mcs_spin_lock_contended(&node->locked); } /* @@ -86,13 +104,9 @@ void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node) while (!(next = ACCESS_ONCE(node->next))) arch_mutex_cpu_relax(); } - /* - * Pass lock to next waiter. - * smp_store_release() provides a memory barrier to ensure - * all operations in the critical section has been completed - * before unlocking. - */ - smp_store_release(&next->locked, 1); + + /* Pass lock to next waiter. */ + arch_mcs_spin_unlock_contended(&next->locked); } #endif /* __LINUX_MCS_SPINLOCK_H */ -- 1.7.11.7 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org