From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758667AbbDXTBr (ORCPT ); Fri, 24 Apr 2015 15:01:47 -0400 Received: from g4t3427.houston.hp.com ([15.201.208.55]:36505 "EHLO g4t3427.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030735AbbDXS55 (ORCPT ); Fri, 24 Apr 2015 14:57:57 -0400 From: Waiman Long To: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra Cc: linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, Paolo Bonzini , Konrad Rzeszutek Wilk , Boris Ostrovsky , "Paul E. McKenney" , Rik van Riel , Linus Torvalds , Raghavendra K T , David Vrabel , Oleg Nesterov , Daniel J Blueman , Scott J Norton , Douglas Hatch , "Peter Zijlstra (Intel)" , Waiman Long Subject: [PATCH v16 07/14] qspinlock: Revert to test-and-set on hypervisors Date: Fri, 24 Apr 2015 14:56:36 -0400 Message-Id: <1429901803-29771-8-git-send-email-Waiman.Long@hp.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1429901803-29771-1-git-send-email-Waiman.Long@hp.com> References: <1429901803-29771-1-git-send-email-Waiman.Long@hp.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra (Intel) When we detect a hypervisor (!paravirt, see qspinlock paravirt support patches), revert to a simple test-and-set lock to avoid the horrors of queue preemption. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Waiman Long --- arch/x86/include/asm/qspinlock.h | 14 ++++++++++++++ include/asm-generic/qspinlock.h | 7 +++++++ kernel/locking/qspinlock.c | 3 +++ 3 files changed, 24 insertions(+), 0 deletions(-) diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h index 222995b..64c925e 100644 --- a/arch/x86/include/asm/qspinlock.h +++ b/arch/x86/include/asm/qspinlock.h @@ -1,6 +1,7 @@ #ifndef _ASM_X86_QSPINLOCK_H #define _ASM_X86_QSPINLOCK_H +#include #include #define queue_spin_unlock queue_spin_unlock @@ -15,6 +16,19 @@ static inline void queue_spin_unlock(struct qspinlock *lock) smp_store_release((u8 *)lock, 0); } +#define virt_queue_spin_lock virt_queue_spin_lock + +static inline bool virt_queue_spin_lock(struct qspinlock *lock) +{ + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) + return false; + + while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0) + cpu_relax(); + + return true; +} + #include #endif /* _ASM_X86_QSPINLOCK_H */ diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h index 315d6dc..bcbbc5e 100644 --- a/include/asm-generic/qspinlock.h +++ b/include/asm-generic/qspinlock.h @@ -111,6 +111,13 @@ static inline void queue_spin_unlock_wait(struct qspinlock *lock) cpu_relax(); } +#ifndef virt_queue_spin_lock +static __always_inline bool virt_queue_spin_lock(struct qspinlock *lock) +{ + return false; +} +#endif + /* * Initializier */ diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 99503ef..fc2e5ab 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -249,6 +249,9 @@ void queue_spin_lock_slowpath(struct qspinlock *lock, u32 val) BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); + if (virt_queue_spin_lock(lock)) + return; + /* * wait for in-progress pending->locked hand-overs * -- 1.7.1