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Subject: Re: [PATCH v2 0/7] swait: Introduce and use swq_has_sleeper()
To: Davidlohr Bueso <dave@stgolabs.net>, mingo@kernel.org,
        peterz@infradead.org
Cc: npiggin@gmail.com, paulmck@linux.vnet.ibm.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Cornelia Huck <cohuck@redhat.com>
References: <20170913200824.28067-1-dave@stgolabs.net>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <ddde4bc5-ba8c-b7ec-717e-5655c8cbe15d@redhat.com>
Date: Fri, 15 Sep 2017 13:53:15 +0200
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On 13/09/2017 22:08, Davidlohr Bueso wrote:
> The following patches fix and/or justify (in baby steps) some of the
> callers. The main exception is s390, which I didn't follow how ->valid_wakeup
> can get hoisted as kvm_vcpu_block does not use that in the wait loop.

valid_wakeup is just an optimization, so it's not a problem.

There seems to be always an atomic_or or set_bit before
kvm_s390_vcpu_wakeup is called (except kvm_s390_idle_wakeup which has no
store at all and doesn't need any serialization).  So my suggestion is
to add an smp__mb_after_atomic in kvm_s390_vcpu_wakeup; I'll let the
s390 guys do it.

Paolo