X-Received: by 10.112.171.41 with SMTP id ar9mr4932650lbc.24.1429902621077; Fri, 24 Apr 2015 12:10:21 -0700 (PDT) X-BeenThere: linux.kernel@googlegroups.com Received: by 10.152.22.134 with SMTP id d6ls501488laf.95.gmail; Fri, 24 Apr 2015 12:10:02 -0700 (PDT) X-Received: by 10.152.184.73 with SMTP id es9mr4934034lac.4.1429902602403; Fri, 24 Apr 2015 12:10:02 -0700 (PDT) MIME-Version: 1.0 Path: rq4ni23131lbb.1!nntp.google.com!goblin1!goblin.stu.neva.ru!news.panservice.it!diesel.cu.mi.it!bofh.it!news.nic.it!robomod From: Waiman Long Newsgroups: linux.kernel Subject: [PATCH v16 07/14] qspinlock: Revert to test-and-set on hypervisors Date: Fri, 24 Apr 2015 21:10:02 +0200 Message-ID: References: X-Original-To: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra X-Mailer: git-send-email 1.7.1 Sender: rob...@news.nic.it List-ID: X-Mailing-List: linux-...@vger.kernel.org Approved: rob...@news.nic.it Lines: 86 Organization: linux.* mail to news gateway X-Original-Cc: linux...@vger.kernel.org, x...@kernel.org, linux-...@vger.kernel.org, virtual...@lists.linux-foundation.org, xen-...@lists.xenproject.org, k...@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 X-Original-Date: Fri, 24 Apr 2015 14:56:36 -0400 X-Original-Message-ID: <1429901803-29771-8-git...@hp.com> X-Original-References: <1429901803-29771-1-git...@hp.com> X-Original-Sender: linux-ker...@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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majo...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/