linux-kernel - [PATCH RFC V7 6/12] xen/pvticketlocks: add xen_nopvspin parameter to disable xen pv ticketlocks

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Message-Id: <20120419201435.5411.86444.sendpatchset@codeblue>
Date:	Fri, 20 Apr 2012 01:44:39 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>
Cc:	Attilio Rao <attilio.rao@...rix.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Virtualization <virtualization@...ts.linux-foundation.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	KVM <kvm@...r.kernel.org>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Andi Kleen <andi@...stfloor.org>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Xen Devel <xen-devel@...ts.xensource.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Andrew Jones <drjones@...hat.com>, Avi Kivity <avi@...hat.com>,
	Stephan Diestelhorst <stephan.diestelhorst@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH RFC V7 6/12]  xen/pvticketlocks: add xen_nopvspin parameter to disable xen pv ticketlocks

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
---
 arch/x86/xen/spinlock.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 982e64b..c9bf890 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -223,12 +223,26 @@ void xen_uninit_lock_cpu(int cpu)
 	unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
 }
 
+static bool xen_pvspin __initdata = true;
+
 void __init xen_init_spinlocks(void)
 {
+	if (!xen_pvspin) {
+		printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
+		return;
+	}
+
 	pv_lock_ops.lock_spinning = xen_lock_spinning;
 	pv_lock_ops.unlock_kick = xen_unlock_kick;
 }
 
+static __init int xen_parse_nopvspin(char *arg)
+{
+	xen_pvspin = false;
+	return 0;
+}
+early_param("xen_nopvspin", xen_parse_nopvspin);
+
 #ifdef CONFIG_XEN_DEBUG_FS
 
 static struct dentry *d_spin_debug;

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