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From: Jan Kiszka <jan.kiszka@siemens.com>
To: Avi Kivity <avi@redhat.com>
Cc: kvm-devel <kvm@vger.kernel.org>, Marcelo Tosatti <mtosatti@redhat.com>
Subject: [PATCH v2 2/2] kvm: x86: Drop useless atomic test from timer function
Date: Tue, 09 Jun 2009 15:37:03 +0200	[thread overview]
Message-ID: <4A2E657F.8080908@siemens.com> (raw)
In-Reply-To: <4A2E2B3B.5020408@siemens.com>

The current code tries to optimize the setting of KVM_REQ_PENDING_TIMER
but used atomic_inc_and_test - which always returns true unless pending
had the invalid value of -1 on entry. This patch drops the test part
preserving the original semantic but expressing it less confusingly.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

 arch/x86/kvm/timer.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/timer.c b/arch/x86/kvm/timer.c
index 36054e9..8dd1a55 100644
--- a/arch/x86/kvm/timer.c
+++ b/arch/x86/kvm/timer.c
@@ -15,9 +15,9 @@ static int __kvm_timer_fn(struct kvm_vcpu *vcpu, struct kvm_timer *ktimer)
 	 * case anyway.
 	 */
 	if (ktimer->reinject || !atomic_read(&ktimer->pending)) {
+		atomic_inc(&ktimer->pending);
 		/* FIXME: this code should not know anything about vcpus */
-		if (!atomic_inc_and_test(&ktimer->pending))
-			set_bit(KVM_REQ_PENDING_TIMER, &vcpu->requests);
+		set_bit(KVM_REQ_PENDING_TIMER, &vcpu->requests);
 	}
 
 	if (waitqueue_active(q))

      parent reply	other threads:[~2009-06-09 13:37 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-06-09  9:28 [PATCH] kvm: x86: Fix racy event propagation in kmv timer Jan Kiszka
2009-06-09 13:37 ` [PATCH v2 1/2] " Jan Kiszka
2009-06-09 13:59   ` Marcelo Tosatti
2009-06-14 11:18     ` Avi Kivity
2009-06-09 13:37 ` Jan Kiszka [this message]

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