Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753434AbbEHN2y (ORCPT ); Fri, 8 May 2015 09:28:54 -0400 Received: from terminus.zytor.com ([198.137.202.10]:48526 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753400AbbEHN2g (ORCPT ); Fri, 8 May 2015 09:28:36 -0400 Date: Fri, 8 May 2015 06:27:21 -0700 From: "tip-bot for Peter Zijlstra (Intel)" Message-ID: Cc: tglx@linutronix.de, mingo@kernel.org, oleg@redhat.com, hpa@zytor.com, raghavendra.kt@linux.vnet.ibm.com, daniel@numascale.com, akpm@linux-foundation.org, paolo.bonzini@gmail.com, david.vrabel@citrix.com, linux-kernel@vger.kernel.org, riel@redhat.com, doug.hatch@hp.com, konrad.wilk@oracle.com, scott.norton@hp.com, boris.ostrovsky@oracle.com, bp@alien8.de, torvalds@linux-foundation.org, paulmck@linux.vnet.ibm.com, Waiman.Long@hp.com, peterz@infradead.org Reply-To: raghavendra.kt@linux.vnet.ibm.com, daniel@numascale.com, hpa@zytor.com, mingo@kernel.org, oleg@redhat.com, tglx@linutronix.de, torvalds@linux-foundation.org, paulmck@linux.vnet.ibm.com, Waiman.Long@hp.com, peterz@infradead.org, bp@alien8.de, boris.ostrovsky@oracle.com, scott.norton@hp.com, konrad.wilk@oracle.com, riel@redhat.com, doug.hatch@hp.com, akpm@linux-foundation.org, paolo.bonzini@gmail.com, david.vrabel@citrix.com, linux-kernel@vger.kernel.org In-Reply-To: <1429901803-29771-8-git-send-email-Waiman.Long@hp.com> References: <1429901803-29771-8-git-send-email-Waiman.Long@hp.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/core] locking/qspinlock: Revert to test-and-set on hypervisors Git-Commit-ID: 2aa79af64263190eec610422b07f60e99a7d230a X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3839 Lines: 112 Commit-ID: 2aa79af64263190eec610422b07f60e99a7d230a Gitweb: http://git.kernel.org/tip/2aa79af64263190eec610422b07f60e99a7d230a Author: Peter Zijlstra (Intel) AuthorDate: Fri, 24 Apr 2015 14:56:36 -0400 Committer: Ingo Molnar CommitDate: Fri, 8 May 2015 12:36:58 +0200 locking/qspinlock: Revert to test-and-set on hypervisors 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 Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Daniel J Blueman Cc: David Vrabel Cc: Douglas Hatch Cc: H. Peter Anvin Cc: Konrad Rzeszutek Wilk Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Paolo Bonzini Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Raghavendra K T Cc: Rik van Riel Cc: Scott J Norton Cc: Thomas Gleixner Cc: virtualization@lists.linux-foundation.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1429901803-29771-8-git-send-email-Waiman.Long@hp.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/qspinlock.h | 14 ++++++++++++++ include/asm-generic/qspinlock.h | 7 +++++++ kernel/locking/qspinlock.c | 3 +++ 3 files changed, 24 insertions(+) diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h index e2aee82..f079b70 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 queued_spin_unlock queued_spin_unlock @@ -15,6 +16,19 @@ static inline void queued_spin_unlock(struct qspinlock *lock) smp_store_release((u8 *)lock, 0); } +#define virt_queued_spin_lock virt_queued_spin_lock + +static inline bool virt_queued_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 569abcd..83bfb87 100644 --- a/include/asm-generic/qspinlock.h +++ b/include/asm-generic/qspinlock.h @@ -111,6 +111,13 @@ static inline void queued_spin_unlock_wait(struct qspinlock *lock) cpu_relax(); } +#ifndef virt_queued_spin_lock +static __always_inline bool virt_queued_spin_lock(struct qspinlock *lock) +{ + return false; +} +#endif + /* * Initializier */ diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 0338721..fd31a47 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -249,6 +249,9 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); + if (virt_queued_spin_lock(lock)) + return; + /* * wait for in-progress pending->locked hand-overs * -- 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/