linux-kernel - [PATCH 09/13] x86/pvticketlocks: we only need to kick if there's waiters

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Message-Id: <a2b685fa9d44cf93fc1d1bf69199f5d355e02f82.1314922370.git.jeremy.fitzhardinge@citrix.com>
Date:	Thu,  1 Sep 2011 17:55:02 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...nel.dk>, Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	KVM <kvm@...r.kernel.org>, Andi Kleen <andi@...stfloor.org>,
	Xen Devel <xen-devel@...ts.xensource.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: [PATCH 09/13] x86/pvticketlocks: we only need to kick if there's waiters

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

If we're releasing the lock into an uncontended state, there's nobody
waiting on it, so there's no need to kick anyone.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 arch/x86/kernel/paravirt-spinlocks.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c
index 21b6986..71b8557 100644
--- a/arch/x86/kernel/paravirt-spinlocks.c
+++ b/arch/x86/kernel/paravirt-spinlocks.c
@@ -47,8 +47,7 @@ void __ticket_unlock_release_slowpath(struct arch_spinlock *lock)
 		    old.head_tail, new.head_tail) != old.head_tail) {
 		/* still people waiting */
 		__ticket_unlock_release(lock);
+		__ticket_unlock_kick(lock, new.tickets.head);
 	}
-
-	__ticket_unlock_kick(lock, new.tickets.head);
 }
 EXPORT_SYMBOL(__ticket_unlock_release_slowpath);
-- 
1.7.6

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