Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754728AbaFRT3D (ORCPT ); Wed, 18 Jun 2014 15:29:03 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:45948 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753724AbaFRT3A (ORCPT ); Wed, 18 Jun 2014 15:29:00 -0400 Date: Wed, 18 Jun 2014 12:40:59 -0400 From: Konrad Rzeszutek Wilk To: Peter Zijlstra Cc: Waiman.Long@hp.com, tglx@linutronix.de, mingo@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, paolo.bonzini@gmail.com, boris.ostrovsky@oracle.com, paulmck@linux.vnet.ibm.com, riel@redhat.com, torvalds@linux-foundation.org, raghavendra.kt@linux.vnet.ibm.com, david.vrabel@citrix.com, oleg@redhat.com, gleb@redhat.com, scott.norton@hp.com, chegu_vinod@hp.com, Peter Zijlstra Subject: Re: [PATCH 08/11] qspinlock: Revert to test-and-set on hypervisors Message-ID: <20140618164059.GA2390@laptop.dumpdata.com> References: <20140615124657.264658593@chello.nl> <20140615130153.940699466@chello.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140615130153.940699466@chello.nl> User-Agent: Mutt/1.5.23 (2014-03-12) X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jun 15, 2014 at 02:47:05PM +0200, Peter Zijlstra wrote: > When we detect a hypervisor (!paravirt, see later patches), revert to Please spell out the name of the patches. > a simple test-and-set lock to avoid the horrors of queue preemption. Heheh. > > Signed-off-by: Peter Zijlstra > --- > arch/x86/include/asm/qspinlock.h | 14 ++++++++++++++ > include/asm-generic/qspinlock.h | 7 +++++++ > kernel/locking/qspinlock.c | 3 +++ > 3 files changed, 24 insertions(+) > > --- 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 > > #if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE) > @@ -20,6 +21,19 @@ static inline void queue_spin_unlock(str > > #endif /* !CONFIG_X86_OOSTORE && !CONFIG_X86_PPRO_FENCE */ > > +#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 */ > --- a/include/asm-generic/qspinlock.h > +++ b/include/asm-generic/qspinlock.h > @@ -98,6 +98,13 @@ static __always_inline void queue_spin_u > } > #endif > > +#ifndef virt_queue_spin_lock > +static __always_inline bool virt_queue_spin_lock(struct qspinlock *lock) > +{ > + return false; > +} > +#endif > + > /* > * Initializier > */ > --- a/kernel/locking/qspinlock.c > +++ b/kernel/locking/qspinlock.c > @@ -247,6 +247,9 @@ void queue_spin_lock_slowpath(struct qsp > > 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 > * > > -- 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/