From mboxrd@z Thu Jan  1 00:00:00 1970
From: Carsten Otte <cotte@de.ibm.com>
Subject: Re: [PATCH 3/6] kvm-s390: make sigp restart return busy when stop
 pending
Date: Mon, 06 Feb 2012 12:53:42 +0100
Message-ID: <4F2FBF46.2090604@de.ibm.com>
References: <1328522347-54635-1-git-send-email-borntraeger@de.ibm.com> <1328522347-54635-4-git-send-email-borntraeger@de.ibm.com>
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Cc: Avi Kivity <avi@redhat.com>, Marcelo Tossati <mtosatti@redhat.com>,
	Alexander Graf <agraf@suse.de>,
	Jens Freimann <jfrei@linux.vnet.ibm.com>,
	Cornelia Huck <cornelia.huck@de.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	KVM <kvm@vger.kernel.org>
To: Christian Borntraeger <borntraeger@de.ibm.com>
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Am 06.02.2012 10:59, schrieb Christian Borntraeger:
> +static int __sigp_restart(struct kvm_vcpu *vcpu, u16 cpu_addr)
> +{
> +	int rc = 0;
> +	struct kvm_s390_float_interrupt *fi =&vcpu->kvm->arch.float_int;
> +
> +	spin_lock(&fi->lock);
> +	if (fi->local_int[cpu_addr]->action_bits&  ACTION_STOP_ON_STOP)
> +		rc = 2; /* busy */
> +	else
> +		VCPU_EVENT(vcpu, 4, "sigp restart %x to handle userspace",
> +			cpu_addr);
> +	spin_unlock(&fi->lock);
> +
> +	return rc;
> +}
>
local_int->action_bits is protected by the local int lock of subject CPU,
as one can see in patch #2 of this series. This is racy.